Provided by: cryptsetup-bin_2.0.4-2ubuntu2_amd64 bug

NAME

       cryptsetup - manage plain dm-crypt and LUKS encrypted volumes

SYNOPSIS

       cryptsetup <options> <action> <action args>

DESCRIPTION

       cryptsetup  is  used  to conveniently setup dm-crypt managed device-mapper mappings. These
       include plain dm-crypt volumes and LUKS volumes.  The  difference  is  that  LUKS  uses  a
       metadata  header and can hence offer more features than plain dm-crypt. On the other hand,
       the header is visible and vulnerable to damage.

       In addition, cryptsetup provides limited support for the use of loop-AES volumes  and  for
       TrueCrypt compatible volumes.

PLAIN DM-CRYPT OR LUKS?

       Unless  you  understand  the cryptographic background well, use LUKS.  With plain dm-crypt
       there are a number of possible user errors that massively decrease  security.  While  LUKS
       cannot fix them all, it can lessen the impact for many of them.

WARNINGS

       A  lot  of  good information on the risks of using encrypted storage, on handling problems
       and on security aspects can be found in the Cryptsetup FAQ.  Read  it.  Nonetheless,  some
       risks deserve to be mentioned here.

       Backup:  Storage  media die. Encryption has no influence on that.  Backup is mandatory for
       encrypted data as well, if the data has any worth. See the Cryptsetup FAQ  for  advice  on
       how to do a backup of an encrypted volume.

       Character  encoding:  If  you  enter a passphrase with special symbols, the passphrase can
       change depending on character encoding. Keyboard settings can also change, which can  make
       blind  input  hard  or impossible. For example, switching from some ASCII 8-bit variant to
       UTF-8 can lead to a different binary encoding  and  hence  different  passphrase  seen  by
       cryptsetup,  even  if  what  you  see on the terminal is exactly the same. It is therefore
       highly recommended to select passphrase characters only from 7-bit ASCII, as the  encoding
       for 7-bit ASCII stays the same for all ASCII variants and UTF-8.

       LUKS  header:  If  the  header of a LUKS volume gets damaged, all data is permanently lost
       unless you have a header-backup.  If a key-slot is damaged, it can only be restored from a
       header-backup  or if another active key-slot with known passphrase is undamaged.  Damaging
       the LUKS header is something people manage to do with surprising frequency. This  risk  is
       the  result  of  a trade-off between security and safety, as LUKS is designed for fast and
       secure wiping by just overwriting header and key-slot area.

       Previously used partitions: If a partition was previously used, it is a very good idea  to
       wipe  filesystem signatures, data, etc. before creating a LUKS or plain dm-crypt container
       on it.  For a quick removal of filesystem signatures, use "wipefs". Take care though  that
       this  may  not remove everything. In particular, MD RAID signatures at the end of a device
       may survive. It also does not remove data. For a full wipe, overwrite the whole  partition
       before container creation. If you do not know how to do that, the cryptsetup FAQ describes
       several options.

BASIC COMMANDS

       The following are valid actions for all supported device types.

       open <device> <name> --type <device_type>

              Opens (creates a mapping with) <name> backed by device <device>.

              Device type can be plain, luks (default), luks1, luks2, loopaes or tcrypt.

              For backward compatibility there are open command aliases:

              create (argument-order <name> <device>): open --type plain
              plainOpen: open --type plain
              luksOpen: open --type luks
              loopaesOpen: open --type loopaes
              tcryptOpen: open --type tcrypt

              <options> are type specific and are described below for  individual  device  types.
              For create, the order of the <name> and <device> options is inverted for historical
              reasons, all other aliases use the standard <device> <name> order.

       close <name>

              Removes the existing mapping <name> and wipes the key from kernel memory.

              For backward compatibility there are close  command  aliases:  remove,  plainClose,
              luksClose,  loopaesClose, tcryptClose (all behaves exactly the same, device type is
              determined automatically from active device).

              <options> can be [--deferred]

       status <name>

              Reports the status for the mapping <name>.

       resize <name>

              Resizes an active mapping <name>.

              If --size (in 512-bytes sectors) is not specified, the size is  computed  from  the
              underlying  device.  For  LUKS  it is the size of the underlying device without the
              area reserved for LUKS header (see data payload offset in luksDump  command).   For
              plain crypt device, the whole device size is used.

              Note  that  this  does not change the raw device geometry, it just changes how many
              sectors of the raw device are represented in the mapped device.

              If cryptsetup detected volume key  for  active  device  loaded  in  kernel  keyring
              service,  resize  action would first try to retrieve the key using a token and only
              if it failed it'd ask for a passphrase to unlock a keyslot (LUKS) or  to  derive  a
              volume  key  again  (plain  mode).  The kernel keyring is used by default for LUKS2
              devices.

              With  LUKS2  device  additional  <options>  can   be   [--token-id,   --token-only,
              --key-slot,     --key-file,     --keyfile-size,     --keyfile-offset,    --timeout,
              --disable-locks, --disable-keyring].

PLAIN MODE

       Plain dm-crypt encrypts the device sector-by-sector with a single, non-salted hash of  the
       passphrase.  No  checks  are  performed,  no  metadata  is  used.  There  is no formatting
       operation.  When the raw device is mapped (opened), the usual  device  operations  can  be
       used  on  the mapped device, including filesystem creation.  Mapped devices usually reside
       in /dev/mapper/<name>.

       The following are valid plain device type actions:

       open --type plain <device> <name>
       create <name> <device> (OBSOLETE syntax)

              Opens (creates a mapping with) <name> backed by device <device>.

              <options> can be [--hash, --cipher, --verify-passphrase, --sector-size, --key-file,
              --keyfile-offset,  --key-size,  --offset,  --skip,  --size,  --readonly,  --shared,
              --allow-discards]

              Example: 'cryptsetup open --type plain /dev/sda10 e1' maps the raw encrypted device
              /dev/sda10  to  the  mapped  (decrypted)  device  /dev/mapper/e1, which can then be
              mounted, fsck-ed or have a filesystem created on it.

LUKS EXTENSION

       LUKS, the Linux Unified Key  Setup,  is  a  standard  for  disk  encryption.   It  adds  a
       standardized header at the start of the device, a key-slot area directly behind the header
       and the bulk data area behind that. The whole set  is  called  a  'LUKS  container'.   The
       device  that  a  LUKS  container resides on is called a 'LUKS device'.  For most purposes,
       both terms can be used interchangeably. But note that when the LUKS header is at a nonzero
       offset in a device, then the device is not a LUKS device anymore, but has a LUKS container
       stored in it at an offset.

       LUKS can manage multiple passphrases that can be individually revoked or changed and  that
       can  be  securely  scrubbed from persistent media due to the use of anti-forensic stripes.
       Passphrases are protected against brute-force and  dictionary  attacks  by  PBKDF2,  which
       implements hash iteration and salting in one function.

       LUKS2  is  a new version of header format that allows additional extensions like different
       PBKDF algorithm or authenticated encryption.  You can format device with LUKS2  header  if
       you  specify  --type  luks2  in luksFormat command.  For activation, the format is already
       recognized automatically.

       Each passphrase, also called a key in this document, is associated  with  one  of  8  key-
       slots.   Key  operations that do not specify a slot affect the first slot that matches the
       supplied passphrase or the first empty slot if a new passphrase is added.

       The <device> parameter can also be specified by a LUKS UUID  in  the  format  UUID=<uuid>.
       Translation to real device name uses symlinks in /dev/disk/by-uuid directory.

       To  specify a detached header, the --header parameter can be used in all LUKS commands and
       always takes precedence over the positional <device> parameter.

       The following are valid LUKS actions:

       luksFormat <device> [<key file>]

              Initializes a LUKS partition and sets the  initial  passphrase  (for  key-slot  0),
              either  via  prompting  or  via  <key  file>.  Note  that if the second argument is
              present, then the passphrase is taken from the file given there, without  the  need
              to  use  the  --key-file  option.  Also  note  that  for  both forms of reading the
              passphrase from a file you can  give  '-'  as  file  name,  which  results  in  the
              passphrase being read from stdin and the safety-question being skipped.

              You can only call luksFormat on a LUKS device that is not mapped.

              To use LUKS2, specify --type luks2.

              <options>  can  be  [--hash, --cipher, --verify-passphrase, --key-size, --key-slot,
              --key-file (takes precedence  over  optional  second  argument),  --keyfile-offset,
              --keyfile-size,    --use-random   |   --use-urandom,   --uuid,   --master-key-file,
              --iter-time,  --header,  --pbkdf-force-iterations,   --force-password,   --disable-
              locks].

              For   LUKS2,   additional   <options>  can  be  [--integrity,  --integrity-no-wipe,
              --sector-size, --label,  --subsystem,  --pbkdf,  --pbkdf-memory,  --pbkdf-parallel,
              --disable-locks, --disable-keyring].

              WARNING:  Doing  a  luksFormat on an existing LUKS container will make all data the
              old container permanently irretrievable unless you have a header backup.

       open --type luks <device> <name>
       luksOpen <device> <name> (old syntax)

              Opens the LUKS device <device> and  sets  up  a  mapping  <name>  after  successful
              verification of the supplied passphrase.

              First,  the  passphrase  is searched in LUKS tokens. If it's not found in any token
              and also the passphrase is not supplied via --key-file, the command prompts for  it
              interactively.

              <options>   can   be  [--key-file,  --keyfile-offset,  --keyfile-size,  --readonly,
              --test-passphrase,  --allow-discards,  --header,   --key-slot,   --master-key-file,
              --token-id, --token-only, --disable-keyring, --disable-locks, --type].

       luksSuspend <name>

              Suspends  an active device (all IO operations will block and accesses to the device
              will wait indefinitely) and wipes the encryption  key  from  kernel  memory.  Needs
              kernel 2.6.19 or later.

              After this operation you have to use luksResume to reinstate the encryption key and
              unblock the device or close to remove the mapped device.

              WARNING: never suspend the device on which the cryptsetup binary resides.

              <options> can be [--header, --disable-locks].

       luksResume <name>

              Resumes  a  suspended  device  and  reinstates   the   encryption   key.    Prompts
              interactively for a passphrase if --key-file is not given.

              <options>   can   be   [--key-file,  --keyfile-size,  --header,  --disable-keyring,
              --disable-locks, --type]

       luksAddKey <device> [<key file with new key>]

              Adds a new passphrase. An existing passphrase must be supplied interactively or via
              --key-file.   The new passphrase to be added can be specified interactively or read
              from the file given as positional argument.

              NOTE: with --unbound option the action  creates  new  unbound  LUKS2  keyslot.  The
              keyslot  cannot  be  used  for  device  activation.   If you don't pass new key via
              --master-key-file option, new random key is generated. Existing passphrase for  any
              active keyslot is not required.

              <options>     can     be     [--key-file,     --keyfile-offset,     --keyfile-size,
              --new-keyfile-offset,    --new-keyfile-size,     --key-slot,     --master-key-file,
              --iter-time, --force-password, --header, --disable-locks, --unbound, --type].

       luksRemoveKey <device> [<key file with passphrase to be removed>]

              Removes  the supplied passphrase from the LUKS device. The passphrase to be removed
              can be specified interactively, as the positional argument or via --key-file.

              <options>  can  be   [--key-file,   --keyfile-offset,   --keyfile-size,   --header,
              --disable-locks, --type]

              WARNING:  If  you  read the passphrase from stdin (without further argument or with
              '-' as an argument to --key-file), batch-mode (-q) will be implicitly  switched  on
              and  no  warning will be given when you remove the last remaining passphrase from a
              LUKS container. Removing the last passphrase makes the LUKS  container  permanently
              inaccessible.

       luksChangeKey <device> [<new key file>]

              Changes  an  existing  passphrase.  The  passphrase  to be changed must be supplied
              interactively or via --key-file.  The new passphrase can be supplied  interactively
              or in a file given as positional argument.

              If  a key-slot is specified (via --key-slot), the passphrase for that key-slot must
              be given and the new passphrase will overwrite the specified key-slot. If  no  key-
              slot  is specified and there is still a free key-slot, then the new passphrase will
              be put into a free key-slot before the key-slot containing the  old  passphrase  is
              purged.  If there is no free key-slot, then the key-slot with the old passphrase is
              overwritten directly.

              WARNING: If a key-slot is overwritten, a media failure during  this  operation  can
              cause  the  overwrite  to fail after the old passphrase has been wiped and make the
              LUKS container inaccessible.

              <options>     can     be     [--key-file,     --keyfile-offset,     --keyfile-size,
              --new-keyfile-offset,  --new-keyfile-size,  --key-slot, --force-password, --header,
              --disable-locks, --type].

       luksConvertKey <device>

              Converts an existing LUKS2 keyslot to new  pbkdf  parameters.  The  passphrase  for
              keyslot  to  be  converted  must be supplied interactively or via --key-file. If no
              --pbkdf parameters are specified LUKS2 default pbkdf values will apply.

              If a keyslot is specified (via --key-slot), the passphrase for that keyslot must be
              given.  If  no keyslot is specified and there is still a free keyslot, then the new
              parameters will be put into a free keyslot before the keyslot  containing  the  old
              parameters  is  purged.  If there is no free keyslot, then the keyslot with the old
              parameters is overwritten directly.

              WARNING: If a keyslot is overwritten, a media failure  during  this  operation  can
              cause  the  overwrite to fail after the old parameters have been wiped and make the
              LUKS container inaccessible.

              <options>  can  be  [--key-file,  --keyfile-offset,   --keyfile-size,   --key-slot,
              --header,    --disable-locks,   --iter-time,   --pbkdf,   --pbkdf-force-iterations,
              --pbkdf-memory, --pbkdf-parallel].

       luksKillSlot <device> <key slot number>

              Wipe the key-slot number <key slot> from the LUKS device. Except running in  batch-
              mode  (-q)  a  remaining  passphrase  must be supplied, either interactively or via
              --key-file.  This command can remove the last remaining key-slot, but  requires  an
              interactive  confirmation  when doing so. Removing the last passphrase makes a LUKS
              container permanently inaccessible.

              <options>  can  be   [--key-file,   --keyfile-offset,   --keyfile-size,   --header,
              --disable-locks, --type].

              WARNING:  If  you  read the passphrase from stdin (without further argument or with
              '-' as an argument to --key-file), batch-mode (-q) will be implicitly  switched  on
              and  no  warning will be given when you remove the last remaining passphrase from a
              LUKS container. Removing the last passphrase makes the LUKS  container  permanently
              inaccessible.

              NOTE:  If there is no passphrase provided (on stdin or through --key-file argument)
              and batch-mode (-q) is active, the key-slot is removed without any other warning.

       erase <device>
       luksErase <device>

              Erase all keyslots and make the LUKS container permanently  inaccessible.   You  do
              not need to provide any password for this operation.

              WARNING: This operation is irreversible.

       luksUUID <device>

              Print the UUID of a LUKS device.
              Set new UUID if --uuid option is specified.

       isLuks <device>

              Returns  true, if <device> is a LUKS device, false otherwise.  Use option -v to get
              human-readable feedback. 'Command successful.'  means the device is a LUKS device.

              By specifying --type you may query for specific LUKS version.

       luksDump <device>

              Dump the header information of a LUKS device.

              If the --dump-master-key option is used, the  LUKS  device  master  key  is  dumped
              instead  of the keyslot info. Together with --master-key-file option, master key is
              dumped to a file instead of standard output. Beware that the master key  cannot  be
              changed without reencryption and can be used to decrypt the data stored in the LUKS
              container without a passphrase and even without the LUKS header. This means that if
              the master key is compromised, the whole device has to be erased to prevent further
              access. Use this option carefully.

              To dump the master key, a passphrase has to be supplied,  either  interactively  or
              via --key-file.

              <options>  can be [--dump-master-key, --key-file, --keyfile-offset, --keyfile-size,
              --header, --disable-locks, --master-key-file, --type].

              WARNING:  If  --dump-master-key  is  used  with  --key-file  and  the  argument  to
              --key-file is '-', no validation question will be asked and no warning given.

       luksHeaderBackup <device> --header-backup-file <file>

              Stores a binary backup of the LUKS header and keyslot area.
              Note: Using '-' as filename writes the header backup to a file named '-'.

              WARNING:  This  backup  file  and  a  passphrase valid at the time of backup allows
              decryption of the LUKS data area, even if  the  passphrase  was  later  changed  or
              removed  from  the  LUKS  device.  Also note that with a header backup you lose the
              ability to securely wipe the LUKS device by just overwriting the  header  and  key-
              slots.  You  either  need  to  securely  erase  all  header  backups in addition or
              overwrite the encrypted data area as well.  The second option is  less  secure,  as
              some sectors can survive, e.g. due to defect management.

       luksHeaderRestore <device> --header-backup-file <file>

              Restores  a  binary  backup  of the LUKS header and keyslot area from the specified
              file.
              Note: Using '-' as filename reads the header backup from a file named '-'.

              WARNING: Header and keyslots will be replaced, only the passphrases from the backup
              will work afterward.

              This  command  requires that the master key size and data offset of the LUKS header
              already on the device and of the header backup match. Alternatively, if there is no
              LUKS header on the device, the backup will also be written to it.

       token <add|remove|import|export> <device>

              Action  add creates new keyring token to enable auto-activation of the device.  For
              the auto-activation, the passphrase must be stored in keyring  with  the  specified
              description.  Usually,  the  passphrase  should  be  stored in user or user-session
              keyring.  The token command is supported only for LUKS2.

              For adding new keyring token, option --key-description  is  mandatory.   Also,  new
              token is assigned to key slot specified with --key-slot option or to all active key
              slots in the case --key-slot option is omitted.

              To remove existing token, specify  the  token  ID  which  should  be  removed  with
              --token-id option.

              WARNING: The action token remove removes any token type, not just keyring type from
              token slot specified by --token-id option.

              Action import can store arbitrary valid token json  in  LUKS2  header.  It  may  be
              passed  via standard input or via file passed in --json-file option. If you specify
              --key-slot then successfully imported token is also assigned to the key slot.

              Action export writes requested token json to a file passed with --json-file  or  to
              standard output.

              <options>    can   be   [--header,   --token-id,   --key-slot,   --key-description,
              --disable-locks, --disable-keyring, --json-file].

       convert <device> --type <format>

              Converts the device between LUKS and LUKS2 format (if  possible).   The  conversion
              will  not  be  performed  if  there  is  an  additional  LUKS2  feature or LUKS has
              unsupported header size.

              WARNING: The convert action can destroy the LUKS header in  the  case  of  a  crash
              during conversion or if a media error occurs.  Always create a header backup before
              performing this operation!

              <options> can be [--header, --type].

       config <device>

              Set permanent configuration options (store to LUKS header).  The config command  is
              supported only for LUKS2.

              The  permanent  options  can be --priority to set priority (normal, prefer, ignore)
              for keyslot (specified by --key-slot) or --label and --subsystem.

              <options> can be [--priority, --label, --subsystem, --key-slot, --header].

loop-AES EXTENSION

       cryptsetup supports mapping loop-AES encrypted partition using a compatibility mode.

       open --type loopaes <device> <name> --key-file <keyfile>
       loopaesOpen <device> <name> --key-file <keyfile>  (old syntax)

              Opens the loop-AES <device> and sets up a mapping <name>.

              If the key file is encrypted with GnuPG, then you  have  to  use  --key-file=-  and
              decrypt it before use, e.g. like this:
              gpg --decrypt <keyfile> | cryptsetup loopaesOpen --key-file=- <device> <name>

              WARNING:  The  loop-AES  extension  cannot use the direct input of key file on real
              terminal because the keys are separated by end-of-line and only part of the  multi-
              key file would be read.
              If you need it in script, just use the pipe redirection:
              echo $keyfile | cryptsetup loopaesOpen --key-file=- <device> <name>

              Use --keyfile-size to specify the proper key length if needed.

              Use  --offset to specify device offset. Note that the units need to be specified in
              number of 512 byte sectors.

              Use --skip to specify the IV offset. If the original device used an offset and  but
              did  not  use  it in IV sector calculations, you have to explicitly use --skip 0 in
              addition to the offset parameter.

              Use --hash to override the default hash function for passphrase hashing  (otherwise
              it is detected according to key size).

              <options>  can  be  [--key-file,  --key-size, --offset, --skip, --hash, --readonly,
              --allow-discards].

       See also section 7 of the FAQ and  http://loop-aes.sourceforge.net  for  more  information
       regarding loop-AES.

TCRYPT (TrueCrypt-compatible and VeraCrypt) EXTENSION

       cryptsetup  supports  mapping  of TrueCrypt, tcplay or VeraCrypt (with --veracrypt option)
       encrypted partition using a native Linux kernel API.  Header formatting and TCRYPT  header
       change is not supported, cryptsetup never changes TCRYPT header on-device.

       TCRYPT extension requires kernel userspace crypto API to be available (introduced in Linux
       kernel 2.6.38).  If you are configuring kernel yourself, enable "User-space interface  for
       symmetric  key cipher algorithms" in "Cryptographic API" section (CRYPTO_USER_API_SKCIPHER
       .config option).

       Because TCRYPT header is encrypted, you  have  to  always  provide  valid  passphrase  and
       keyfiles.

       Cryptsetup  should  recognize  all  header variants, except legacy cipher chains using LRW
       encryption mode with 64 bits  encryption  block  (namely  Blowfish  in  LRW  mode  is  not
       recognized, this is limitation of kernel crypto API).

       To  recognize  a VeraCrypt device use the --veracrypt option.  VeraCrypt is just extension
       of TrueCrypt header with increased iteration count so unlocking can take quite  a  lot  of
       time (in comparison with TCRYPT device).

       To  open  a  VeraCrypt  device  with  a  custom Personal Iteration Multiplier (PIM) value,
       additionally to --veracrypt  use  either  the  --veracrypt-pim=<PIM>  option  to  directly
       specify  the  PIM on the command- line or use --veracrypt-query-pim to be prompted for the
       PIM.

       The PIM value affects the number of iterations applied during key derivation. Please refer
       to   https://www.veracrypt.fr/en/Personal%20Iterations%20Multiplier%20%28PIM%29.html   for
       more detailed information.

       NOTE: Activation with tcryptOpen is supported only for cipher  chains  using  LRW  or  XTS
       encryption modes.

       The  tcryptDump  command should work for all recognized TCRYPT devices and doesn't require
       superuser privilege.

       To map system device (device with boot loader where the whole  encrypted  system  resides)
       use --tcrypt-system option.  You can use partition device as the parameter (parameter must
       be real partition device, not an image in a file), then only this partition is mapped.

       If you have the whole TCRYPT device as a file image and you want to map multiple partition
       encrypted  with  system  encryption,  please create loopback mapping with partitions first
       (losetup -P, see losetup(8) man page for more info), and use loop partition as the  device
       parameter.

       If  you  use  the  whole  base  device  as  a  parameter,  one device for the whole system
       encryption is mapped. This mode is available only for backward  compatibility  with  older
       cryptsetup versions which mapped TCRYPT system encryption using the whole device.

       To use hidden header (and map hidden device, if available), use --tcrypt-hidden option.

       To explicitly use backup (secondary) header, use --tcrypt-backup option.

       NOTE:  There  is  no  protection  for  a hidden volume if the outer volume is mounted. The
       reason is that if there were any protection, it would  require  some  metadata  describing
       what to protect in the outer volume and the hidden volume would become detectable.

       open --type tcrypt <device> <name>
       tcryptOpen <device> <name>  (old syntax)

              Opens the TCRYPT (a TrueCrypt-compatible) <device> and sets up a mapping <name>.

              <options>  can  be  [--key-file, --tcrypt-hidden, --tcrypt-system, --tcrypt-backup,
              --readonly,  --test-passphrase,  --allow-discards,  --veracrypt,   --veracrypt-pim,
              --veracrypt-query-pim].

              The  keyfile parameter allows a combination of file content with the passphrase and
              can be repeated. Note  that  using  keyfiles  is  compatible  with  TCRYPT  and  is
              different from LUKS keyfile logic.

              WARNING:  Option  --allow-discards  cannot be combined with option --tcrypt-hidden.
              For normal mapping, it can cause the destruction of hidden  volume  (hidden  volume
              appears as unused space for outer volume so this space can be discarded).

       tcryptDump <device>

              Dump the header information of a TCRYPT device.

              If  the  --dump-master-key  option  is used, the TCRYPT device master key is dumped
              instead of TCRYPT header info. Beware that the master key (or  concatenated  master
              keys  if cipher chain is used) can be used to decrypt the data stored in the TCRYPT
              container without a passphrase.  This means that if the master key is  compromised,
              the  whole  device  has  to  be  erased  to prevent further access. Use this option
              carefully.

              <options> can be [--dump-master-key, --key-file, --tcrypt-hidden,  --tcrypt-system,
              --tcrypt-backup].

              The  keyfile parameter allows a combination of file content with the passphrase and
              can be repeated.

       See also https://en.wikipedia.org/wiki/TrueCrypt for more information regarding TrueCrypt.

       Please note that cryptsetup does not  use  TrueCrypt  code,  please  report  all  problems
       related to this compatibility extension to the cryptsetup project.

MISCELLANEOUS

       repair <device>

              Tries  to repair the device metadata if possible. Currently supported only for LUKS
              device type.

              This command is useful to fix some known benign LUKS metadata  header  corruptions.
              Only basic corruptions of unused keyslot are fixable. This command will only change
              the LUKS header, not any key-slot data. You may  enforce  LUKS  version  by  adding
              --type option.

              WARNING:  Always  create a binary backup of the original header before calling this
              command.

       benchmark <options>

              Benchmarks ciphers and KDF (key derivation function).  Without parameters, it tries
              to measure few common configurations.

              To  benchmark  other  ciphers or modes, you need to specify --cipher and --key-size
              options or --hash for KDF test.

              NOTE: This benchmark is using memory only and  is  only  informative.   You  cannot
              directly predict real storage encryption speed from it.

              For  testing  block ciphers, this benchmark requires kernel userspace crypto API to
              be available (introduced in Linux kernel 2.6.38).  If you  are  configuring  kernel
              yourself,  enable  "User-space  interface  for  symmetric key cipher algorithms" in
              "Cryptographic API" section (CRYPTO_USER_API_SKCIPHER .config option).

              <options> can be [--cipher, --key-size, --hash].

OPTIONS

       --verbose, -v
              Print more information on command execution.

       --debug
              Run in debug mode with full diagnostic logs. Debug output lines are always prefixed
              by '#'.

       --type <device-type>
              Specifies required device type, for more info read BASIC COMMANDS section.

       --hash, -h <hash-spec>
              Specifies the passphrase hash for open (for plain and loopaes device types).

              Specifies  the  hash  used  in  the LUKS key setup scheme and volume key digest for
              luksFormat. The specified hash is used as hash-parameter for PBKDF2 and for the  AF
              splitter.

              The  specified  hash  name  is passed to the compiled-in crypto backend.  Different
              backends may support different hashes.  For luksFormat,  the  hash  algorithm  must
              provide  at  least 160 bits of output, which excludes, e.g., MD5. Do not use a non-
              crypto hash like "crc32" as this breaks security.

              Values compatible with old version of cryptsetup are "ripemd160"  for  open  --type
              plain and "sha1" for luksFormat.

              Use cryptsetup --help to show the defaults.

       --cipher, -c <cipher-spec>
              Set the cipher specification string.

              cryptsetup  --help  shows  the  compiled-in  defaults.   The current default in the
              distributed sources is "aes-cbc-essiv:sha256"  for  plain  dm-crypt  and  "aes-xts-
              plain64" for LUKS.

              If  a  hash  is part of the cipher specification, then it is used as part of the IV
              generation. For example, ESSIV needs a hash function, while "plain64" does not  and
              hence none is specified.

              For  XTS mode you can optionally set a key size of 512 bits with the -s option. Key
              size for XTS mode is twice that for other modes for the same security level.

              XTS mode requires kernel 2.6.24 or later and  plain64  requires  kernel  2.6.33  or
              later. More information can be found in the FAQ.

       --verify-passphrase, -y
              When  interactively  asking for a passphrase, ask for it twice and complain if both
              inputs do not match. Advised when creating a regular mapping for the first time, or
              when running luksFormat. Ignored on input from file or stdin.

       --key-file, -d name
              Read the passphrase from file.

              If  the  name  given  is "-", then the passphrase will be read from stdin.  In this
              case, reading will not stop at newline characters.

              With LUKS, passphrases supplied via --key-file are always the existing  passphrases
              requested  by  a  command,  except  in  the  case of luksFormat where --key-file is
              equivalent to the positional key file argument.

              If you want to set a new passphrase via key file, you  have  to  use  a  positional
              argument to luksAddKey.

              See section NOTES ON PASSPHRASE PROCESSING for more information.

       --keyfile-offset value
              Skip  value  bytes  at the beginning of the key file.  Works with all commands that
              accept key files.

       --keyfile-size, -l value
              Read a maximum of value bytes from the key file.  The default is to read the  whole
              file  up to the compiled-in maximum that can be queried with --help. Supplying more
              data than the compiled-in maximum aborts the operation.

              This option is useful to cut trailing newlines, for example. If --keyfile-offset is
              also  given,  the size count starts after the offset.  Works with all commands that
              accept key files.

       --new-keyfile-offset value
              Skip value bytes at the start when adding a  new  passphrase  from  key  file  with
              luksAddKey.

       --new-keyfile-size  value
              Read  a  maximum  of  value  bytes  when adding a new passphrase from key file with
              luksAddKey.  The default is to read the whole file up to  the  compiled-in  maximum
              length  that  can  be  queried  with  --help.   Supplying more than the compiled in
              maximum aborts the operation.  When --new-keyfile-offset  is  also  given,  reading
              starts after the offset.

       --master-key-file
              Use a master key stored in a file.

              For luksFormat this allows creating a LUKS header with this specific master key. If
              the master key was taken from an existing LUKS header and all other parameters  are
              the  same,  then  the  new  header  decrypts the data encrypted with the header the
              master key was taken from.

              Action luksDump together with --dump-master-key option: The volume (master) key  is
              stored in a file instead of being printed out to standard output.

              WARNING:  If  you create your own master key, you need to make sure to do it right.
              Otherwise, you can end up with a low-entropy  or  otherwise  partially  predictable
              master key which will compromise security.

              For  luksAddKey  this  allows  adding  a  new  passphrase without having to know an
              existing one.

              For open this allows one to open the LUKS device without giving a passphrase.

       --dump-master-key
              For luksDump this option includes the master key in the displayed information.  Use
              with care, as the master key can be used to bypass the passphrases, see also option
              --master-key-file.

       --json-file
              Read token json from a file or write  token  to  it.  See  token  action  for  more
              information.  --json-file=- reads json from standard input or writes it to standard
              output respectively.

       --use-random

       --use-urandom
              For luksFormat these options define which kernel random number  generator  will  be
              used to create the master key (which is a long-term key).

              See  NOTES  ON RANDOM NUMBER GENERATORS for more information. Use cryptsetup --help
              to show the compiled-in default random number generator.

              WARNING: In a low-entropy situation (e.g. in an embedded system),  both  selections
              are  problematic.  Using /dev/urandom can lead to weak keys.  Using /dev/random can
              block a long time, potentially forever, if not enough entropy can be  harvested  by
              the kernel.

       --key-slot, -S <0-7>
              For LUKS operations that add key material, this options allows you to specify which
              key slot is selected for the new key.  This option can be used for luksFormat,  and
              luksAddKey.
              In  addition,  for  open,  this  option  selects a specific key-slot to compare the
              passphrase against.  If the given passphrase would only match a different key-slot,
              the operation fails.

       --key-size, -s <bits>
              Sets  key  size  in bits. The argument has to be a multiple of 8. The possible key-
              sizes are limited by the cipher and mode used.

              See /proc/crypto for more information. Note that key-size in /proc/crypto is stated
              in bytes.

              This  option  can  be  used  for  open  --type plain or luksFormat.  All other LUKS
              actions will use the key-size specified in the LUKS header.  Use cryptsetup  --help
              to show the compiled-in defaults.

       --size, -b <number of 512 byte sectors>
              Set  the  size of the device in sectors of 512 bytes.  This option is only relevant
              for the open and resize actions.

       --offset, -o <number of 512 byte sectors>
              Start offset in the backend device  in  512-byte  sectors.   This  option  is  only
              relevant for the open action with plain or loopaes device types.

       --skip, -p <number of 512 byte sectors>
              Start  offset  used  in IV calculation in 512-byte sectors (how many sectors of the
              encrypted data to skip at the beginning).  This option is  only  relevant  for  the
              open action with plain or loopaes device types.

              Hence,  if  --offset  n,  and --skip s, sector n (the first sector of the encrypted
              device) will get a sector number of s for the IV calculation.

       --readonly, -r
              set up a read-only mapping.

       --shared
              Creates an additional mapping for one common ciphertext device. Arbitrary  mappings
              are  supported.  This option is only relevant for the open --type plain action. Use
              --offset, --size and --skip to specify the mapped area.

       --pbkdf <PBKDF spec>
              Set Password-Based Key Derivation Function (PBKDF) algorithm for LUKS keyslot.  The
              PBKDF  can  be:  pbkdf2  (for  PBKDF2 according to RFC2898), argon2i for Argon2i or
              argon2id for  Argon2id  (see  https://www.cryptolux.org/index.php/Argon2  for  more
              info).

              For  LUKS1,  only  PBKDF2  is  accepted  (no need to use this option).  The default
              PBKDF2 for LUKS2 is set during compilation time  and  is  available  in  cryptsetup
              --help output.

              A  PBKDF  is used for increasing dictionary and brute-force attack cost for keyslot
              passwords. The parameters can be time, memory and parallel cost.

              For PBKDF2, only time cost (number of iterations) applies.  For  Argon2i/id,  there
              is  also  memory  cost  (memory  required during the process of key derivation) and
              parallel cost (number of threads that run in parallel during the key derivation.

              Note that increasing memory cost also increases time, so the final parameter values
              are   measured  by  a  benchmark.  The  benchmark  tries  to  find  iteration  time
              (--iter-time) with required memory cost --pbkdf-memory. If it is not possible,  the
              memory  cost is decreased as well.  The parallel cost --pbkdf-parallel is constant,
              is is checked against available CPU cores (if not available, it is  decreased)  and
              the maximum parallel cost is 4.

              You  can  see  all  PBKDF  parameters  for  particular  LUKS2 keyslot with luksDump
              command.

              NOTE: If you do not want to use  benchmark  and  want  to  specify  all  parameters
              directly,  use  --pbkdf-force-iterations  with --pbkdf-memory and --pbkdf-parallel.
              This will override the values without benchmarking.  Note it  can  cause  extremely
              long unlocking time. Use only is specified cases, for example, if you know that the
              formatted device will be used on some small embedded system.   In  this  case,  the
              LUKS PBKDF2 digest will be set to the minimum iteration count.

       --iter-time, -i <number of milliseconds>
              The  number of milliseconds to spend with PBKDF passphrase processing.  This option
              is only relevant for LUKS operations  that  set  or  change  passphrases,  such  as
              luksFormat  or  luksAddKey.   Specifying  0  as  parameter  selects the compiled-in
              default.

       --pbkdf-memory <number>
              Set the memory cost for PBKDF (for Argon2i/id  the  number  represents  kilobytes).
              Note  that  it  is  maximal value, PBKDF benchmark or available physical memory can
              decrease it.  This option is not available for PBKDF2.

       --pbkdf-parallel <number>
              Set the parallel cost for PBKDF (number of threads, up to  4).   Note  that  it  is
              maximal  value,  it  is decreased automatically if CPU online count is lower.  This
              option is not available for PBKDF2.

       --pbkdf-force-iterations <num>
              Avoid PBKDF benchmark and set time cost (iterations) directly.  It can be used  for
              LUKS/LUKS2 device only.  See --pbkdf option for more info.

       --batch-mode, -q
              Suppresses all confirmation questions. Use with care!

              If  the  -y  option  is not specified, this option also switches off the passphrase
              verification for luksFormat.

       --progress-frequency <seconds>
              Print separate line every <seconds> with wipe progress.

       --timeout, -t <number of seconds>
              The number of seconds to wait before timeout on passphrase input via  terminal.  It
              is  relevant  every time a passphrase is asked, for example for open, luksFormat or
              luksAddKey.  It has no effect if used in conjunction with --key-file.
              This option is useful when the system should not stall if the user does not input a
              passphrase,  e.g.  during boot. The default is a value of 0 seconds, which means to
              wait forever.

       --tries, -T
              How often the input of the passphrase shall be retried.  This  option  is  relevant
              every  time  a passphrase is asked, for example for open, luksFormat or luksAddKey.
              The default is 3 tries.

       --align-payload <number of 512 byte sectors>
              Align payload at a boundary of value 512-byte sectors.  This option is relevant for
              luksFormat.

              If  not specified, cryptsetup tries to use the topology info provided by the kernel
              for the underlying device to get the optimal alignment.  If not available  (or  the
              calculated value is a multiple of the default) data is by default aligned to a 1MiB
              boundary (i.e. 2048 512-byte sectors).

              For a detached LUKS header, this option specifies the offset on  the  data  device.
              See also the --header option.

       --uuid=UUID
              Use  the  provided UUID for the luksFormat command instead of generating a new one.
              Changes the existing UUID when used with the luksUUID command.

              The   UUID   must   be   provided   in   the    standard    UUID    format,    e.g.
              12345678-1234-1234-1234-123456789abc.

       --allow-discards
              Allow  the  use  of  discard  (TRIM)  requests for the device.  This option is only
              relevant for open action.

              WARNING: This command can have a negative  security  impact  because  it  can  make
              filesystem-level   operations   visible   on  the  physical  device.  For  example,
              information leaking filesystem type, used space, etc. may be extractable  from  the
              physical  device  if the discarded blocks can be located later. If in doubt, do not
              use it.

              A kernel version of 3.1 or later is needed. For earlier  kernels,  this  option  is
              ignored.

       --perf-same_cpu_crypt
              Perform  encryption using the same cpu that IO was submitted on.  The default is to
              use an unbound workqueue so that encryption work is automatically balanced  between
              available CPUs.  This option is only relevant for open action.

              NOTE:  This option is available only for low-level dm-crypt performance tuning, use
              only if you need a change to default dm-crypt behaviour. Needs kernel 4.0 or later.

       --perf-submit_from_crypt_cpus
              Disable offloading writes to a separate thread after encryption.   There  are  some
              situations  where  offloading  write  bios  from the encryption threads to a single
              thread degrades performance significantly.  The default is to offload write bios to
              the same thread.  This option is only relevant for open action.

              NOTE:  This option is available only for low-level dm-crypt performance tuning, use
              only if you need a change to default dm-crypt behaviour. Needs kernel 4.0 or later.

       --test-passphrase
              Do not activate the device, just verify passphrase.  This option is  only  relevant
              for open action (the device mapping name is not mandatory if this option is used).

       --header <device or file storing the LUKS header>
              Use a detached (separated) metadata device or file where the LUKS header is stored.
              This option allows one to store ciphertext and LUKS header on different devices.

              This option is only relevant for LUKS devices and can be used with the  luksFormat,
              open, luksSuspend, luksResume, status and resize commands.

              For  luksFormat  with  a  file  name  as the argument to --header, the file will be
              automatically created if it does not exist.  See the cryptsetup FAQ for header size
              calculation.

              For  other  commands  that  change  the  LUKS header (e.g. luksAddKey), specify the
              device or file with the LUKS header directly as the LUKS device.

              If used with luksFormat, the --align-payload option is  taken  as  absolute  sector
              alignment on ciphertext device and can be zero.

              WARNING: There is no check whether the ciphertext device specified actually belongs
              to the header given. In fact, you can specify an arbitrary device as the ciphertext
              device for open with the --header option. Use with care.

       --header-backup-file <file>
              Specify file with header backup for luksHeaderBackup or luksHeaderBackup actions.

       --force-password
              Do not use password quality checking for new LUKS passwords.

              This option applies only to luksFormat, luksAddKey and luksChangeKey and is ignored
              if cryptsetup is built without password quality checking support.

              For  more  info  about  password  quality  check,   see   the   manual   page   for
              pwquality.conf(5) and passwdqc.conf(5).

       --deferred
              Defers device removal in close command until the last user closes it.

       --disable-locks
              Disable  lock protection for metadata on disk.  This option is valid only for LUKS2
              and ignored for other formats.

              WARNING: Do not  use  this  option  unless  you  run  cryptsetup  in  a  restricted
              environment  where locking is impossible to perform (where /run directory cannot be
              used).

       --disable-keyring
              Do not load volume key in kernel keyring but use store key directly in the dm-crypt
              target.  This option is supported only for the LUKS2 format.

       --key-description <text>
              Set key description in keyring for use with token command.

       --priority <normal|prefer|ignore>
              Set  a  priority  for  LUKS2  keyslot.   The prefer priority marked slots are tried
              before normal priority.  The ignored priority means, that slot is  never  used,  if
              not explicitly requested by --key-slot option.

       --token-id
              Specify  what  token  to  use  in  actions  token, open or resize.  If omitted, all
              available tokens will be checked before proceeding further with passphrase prompt.

       --token-only
              Do not proceed further with  action  (any  of  token,  open  or  resize)  if  token
              activation  failed.  Without  the  option,  action  asks  for passphrase to proceed
              further.

       --sector-size <bytes>
              Set sector size for use with disk encryption. It must be power of two and in  range
              512  - 4096 bytes. The default is 512 bytes sectors.  This option is available only
              in the LUKS2 mode.

              Note that if sector size is higher than underlying device hardware sector and there
              is  not integrity protection that uses data journal, using this option can increase
              risk on incomplete sector writes during a power fail.

              If used together with --integrity option and dm-integrity journal, the atomicity of
              writes  is  guaranteed in all cases (but it cost write performance - data has to be
              written twice).

              Increasing sector size from 512 bytes to 4096 bytes can provide better  performance
              on   most  of  the  modern  storage  devices  and  also  with  some  hw  encryption
              accelerators.

       --persistent
              If used with LUKS2  devices  and  activation  commands  like  open,  the  specified
              activation  flags  are  persistently  written  into  metadata  and  used  next time
              automatically even for normal activation.  (No need to use cryptab or other  system
              configuration     files.)      Only     --allow-discards,    --perf-same_cpu_crypt,
              --perf-submit_from_crypt_cpus   and   --integrity-no-journal    can    be    stored
              persistently.

       --label <LABEL>
              --subsystem  <SUBSYSTEM>  Set label and subsystem description for LUKS2 device, can
              be used in config and format actions.  The label and subsystem are optional  fields
              and  can  be  later  used  in  udev scripts for triggering user actions once device
              marked by these labels is detected.

       --integrity <integrity algorithm>
              Specify integrity algorithm to be used for authenticated disk encryption in LUKS2.

              WARNING: This extension is EXPERIMENTAL and  requires  dm-integrity  kernel  target
              (available  since  kernel  version  4.12).   For  more info, see AUTHENTICATED DISK
              ENCRYPTION section.

       --integrity-no-journal
              Activate device with integrity protection without using data journal (direct  write
              of  data  and integrity tags).  Note that without journal power fail can cause non-
              atomic write and data corruption.  Use  only  if  journalling  is  performed  on  a
              different storage layer.

       --integrity-no-wipe
              Skip  wiping  of  device  authentication  (integrity)  tags. If you skip this step,
              sectors will report invalid integrity tag until an application write to the sector.

              NOTE: Even some writes to the device can fail if the write is not aligned  to  page
              size and page-cache initiates read of a sector with invalid integrity tag.

       --unbound

              Creates new LUKS2 unbound keyslot. See luksAddKey action for more details.

       --tcrypt-hidden
              --tcrypt-system --tcrypt-backup Specify which TrueCrypt on-disk header will be used
              to open the device.  See TCRYPT section for more info.

       --veracrypt
              Allow VeraCrypt compatible mode. Only for TCRYPT extension.  See TCRYPT section for
              more info.

       --veracrypt-pim
              --veracrypt-query-pim   Use  a  custom  Personal  Iteration  Multiplier  (PIM)  for
              VeraCrypt device.  See TCRYPT section for more info.

       --version
              Show the program version.

       --usage
              Show short option help.

       --help, -?
              Show help text and default parameters.

RETURN CODES

       Cryptsetup returns 0 on success and a non-zero value on error.

       Error codes are: 1 wrong parameters, 2 no permission (bad passphrase), 3 out of memory,  4
       wrong device specified, 5 device already exists or device is busy.

NOTES ON PASSPHRASE PROCESSING FOR PLAIN MODE

       Note that no iterated hashing or salting is done in plain mode.  If hashing is done, it is
       a single direct hash. This means that low-entropy passphrases are easy to attack in  plain
       mode.

       From  a  terminal:  The  passphrase is read until the first newline, i.e. '\n'.  The input
       without the newline character is processed with the default hash  or  the  hash  specified
       with --hash.  The hash result will be truncated to the key size of the used cipher, or the
       size specified with -s.

       From stdin: Reading will continue until a newline (or until  the  maximum  input  size  is
       reached),  with  the  trailing  newline stripped. The maximum input size is defined by the
       same compiled-in default as for the maximum key file size and  can  be  overwritten  using
       --keyfile-size option.

       The data read will be hashed with the default hash or the hash specified with --hash.  The
       hash result will be truncated to the key size of the used cipher, or  the  size  specified
       with -s.

       Note  that  if  --key-file=- is used for reading the key from stdin, trailing newlines are
       not stripped from the input.

       If "plain" is used as argument to --hash, the input data will not be hashed.  Instead,  it
       will  be  zero  padded (if shorter than the key size) or truncated (if longer than the key
       size) and used directly as the binary key. This is useful for directly specifying a binary
       key.   No warning will be given if the amount of data read from stdin is less than the key
       size.

       From a key file: It will be truncated to the key size of the used cipher or the size given
       by -s and directly used as a binary key.

       WARNING: The --hash argument is being ignored.  The --hash option is usable only for stdin
       input in plain mode.

       If the key file is shorter than the key, cryptsetup will quit with an error.  The  maximum
       input size is defined by the same compiled-in default as for the maximum key file size and
       can be overwritten using --keyfile-size option.

NOTES ON PASSPHRASE PROCESSING FOR LUKS

       LUKS uses PBKDF2 to protect against dictionary attacks and to give some protection to low-
       entropy passphrases (see RFC 2898 and the cryptsetup FAQ).

       From  a  terminal:  The  passphrase  is read until the first newline and then processed by
       PBKDF2 without the newline character.

       From stdin: LUKS will read passphrases from stdin up to the first newline character or the
       compiled-in maximum key file length. If --keyfile-size is given, it is ignored.

       From  key  file:  The complete keyfile is read up to the compiled-in maximum size. Newline
       characters do not terminate the input. The --keyfile-size option can be used to limit what
       is read.

       Passphrase  processing:  Whenever  a  passphrase  is  added  to a LUKS header (luksAddKey,
       luksFormat), the user may specify how much  the  time  the  passphrase  processing  should
       consume.  The  time  is  used to determine the iteration count for PBKDF2 and higher times
       will offer better protection for low-entropy passphrases, but open  will  take  longer  to
       complete.  For  passphrases  that  have  entropy  higher  than the used key length, higher
       iteration times will not increase security.

       The default setting of one or two seconds is sufficient for most practical cases. The only
       exception  is  a  low-entropy  passphrase  used  on a device with a slow CPU, as this will
       result in a low iteration count. On a slow device, it may be  advisable  to  increase  the
       iteration  time  using the --iter-time option in order to obtain a higher iteration count.
       This does slow down all later luksOpen operations accordingly.

INCOHERENT BEHAVIOR FOR INVALID PASSPHRASES/KEYS

       LUKS checks for a valid passphrase when an encrypted partition is unlocked.  The  behavior
       of  plain dm-crypt is different.  It will always decrypt with the passphrase given. If the
       given passphrase is wrong, the device mapped by  plain  dm-crypt  will  essentially  still
       contain encrypted data and will be unreadable.

NOTES ON SUPPORTED CIPHERS, MODES, HASHES AND KEY SIZES

       The  available  combinations  of  ciphers,  modes,  hashes  and key sizes depend on kernel
       support. See /proc/crypto for a  list  of  available  options.  You  might  need  to  load
       additional kernel crypto modules in order to get more options.

       For  the  --hash option, if the crypto backend is libgcrypt, then all algorithms supported
       by the gcrypt library are available.  For other crypto backends, some  algorithms  may  be
       missing.

NOTES ON PASSPHRASES

       Mathematics  can't  be  bribed. Make sure you keep your passphrases safe.  There are a few
       nice tricks for constructing a fallback, when suddenly out of the blue, your brain refuses
       to cooperate.  These fallbacks need LUKS, as it's only possible with LUKS to have multiple
       passphrases. Still, if your attacker model does not prevent it, storing your passphrase in
       a sealed envelope somewhere may be a good idea as well.

NOTES ON RANDOM NUMBER GENERATORS

       Random  Number  Generators (RNG) used in cryptsetup are always the kernel RNGs without any
       modifications or additions to data stream produced.

       There are two types of randomness cryptsetup/LUKS  needs.  One  type  (which  always  uses
       /dev/urandom) is used for salts, the AF splitter and for wiping deleted keyslots.

       The  second  type  is  used  for  the  volume  (master)  key. You can switch between using
       /dev/random and /dev/urandom  here, see  --use-random  and  --use-urandom  options.  Using
       /dev/random on a system without enough entropy sources can cause luksFormat to block until
       the requested amount of random data is gathered.  In  a  low-entropy  situation  (embedded
       system),  this  can take a very long time and potentially forever. At the same time, using
       /dev/urandom in a low-entropy situation will produce low-quality keys. This is  a  serious
       problem,  but  solving  it  is  out of scope for a mere man-page.  See urandom(4) for more
       information.

AUTHENTICATED DISK ENCRYPTION (EXPERIMENTAL)

       Since Linux kernel version 4.12 dm-crypt supports authenticated disk encryption.

       Normal disk encryption modes are length-preserving (plaintext sector is of the  same  size
       as  a  ciphertext  sector)  and  can  provide  only  confidentiality  protection,  but not
       cryptographically sound data integrity protection.

       Authenticated modes require additional space per-sector for  authentication  tag  and  use
       Authenticated Encryption with Additional Data (AEAD) algorithms.

       If  you configure LUKS2 device with data integrity protection, there will be an underlying
       dm-integrity device, which provides additional per-sector metadata space and also  provide
       data  journal  protection  to ensure atomicity of data and metadata update.  Because there
       must be additional space for metadata and journal, the available space for the device will
       be smaller than for length-preserving modes.

       The dm-crypt device then resides on top of such a dm-integrity device.  All activation and
       deactivation of this device stack is performed by cryptsetup, there is  no  difference  in
       using  luksOpen  for integrity protected devices.  If you want to format LUKS2 device with
       data integrity protection, use --integrity option.

       Some  integrity  modes  requires  two  independent  keys  (key  for  encryption  and   for
       authentication). Both these keys are stored in one LUKS keyslot.

       WARNING: All support for authenticated modes is experimental and there are only some modes
       available for now. Note that there are a very few authenticated encryption algorithms that
       are suitable for disk encryption.

NOTES ON LOOPBACK DEVICE USE

       Cryptsetup  is  usually  used  directly  on a block device (disk partition or LVM volume).
       However, if the device argument is a file, cryptsetup tries to allocate a loopback  device
       and  map  it  into  this file. This mode requires Linux kernel 2.6.25 or more recent which
       supports the loop autoclear flag (loop device is cleared on the last close automatically).
       Of course, you can always map a file to a loop-device manually. See the cryptsetup FAQ for
       an example.

       When device mapping is active, you can see the loop backing file  in  the  status  command
       output. Also see losetup(8).

LUKS2 header locking

       The  LUKS2  on-disk  metadata  is  updated  in  several steps and to achieve proper atomic
       update, there is a locking mechanism.  For an image in file,  code  uses  flock(2)  system
       call.   For  a  block  device,  lock  is performed over a special file stored in a locking
       directory (by default /run/lock/cryptsetup).  The locking directory should be created with
       the proper security context by the distribution during the boot-up phase.  Only LUKS2 uses
       locks, other formats do not use this mechanism.

DEPRECATED ACTIONS

       The reload action is no longer supported.  Please use dmsetup(8) if you need  to  directly
       manipulate with the device mapping table.

       The luksDelKey was replaced with luksKillSlot.

REPORTING BUGS

       Report  bugs,  including ones in the documentation, on the cryptsetup mailing list at <dm-
       crypt@saout.de> or in the 'Issues' section on LUKS website.  Please attach the  output  of
       the failed command with the --debug option added.

AUTHORS

       cryptsetup originally written by Jana Saout <jana@saout.de>
       The   LUKS   extensions   and   original  man  page  were  written  by  Clemens  Fruhwirth
       <clemens@endorphin.org>.
       Man page extensions by Milan Broz <gmazyland@gmail.com>.
       Man page rewrite and extension by Arno Wagner <arno@wagner.name>.

COPYRIGHT

       Copyright © 2004 Jana Saout
       Copyright © 2004-2006 Clemens Fruhwirth
       Copyright © 2009-2018 Red Hat, Inc.
       Copyright © 2009-2018 Milan Broz
       Copyright © 2012-2014 Arno Wagner

       This is free software; see the source for copying conditions.  There is NO  warranty;  not
       even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO

       The LUKS website at https://gitlab.com/cryptsetup/cryptsetup/

       The   cryptsetup   FAQ,   contained   in   the   distribution   package   and   online  at
       https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions

       The cryptsetup mailing list and list archive, see FAQ entry 1.6.

       The       LUKS       on-disk        format        specification        available        at
       https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification