Provided by: cryptsetup-bin_1.6.1-1ubuntu1_amd64 bug


       cryptsetup - manage plain dm-crypt and LUKS encrypted volumes


       cryptsetup <options> <action> <action args>


       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.


       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.


       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 backup of an encrypted volume.

       Character encoding: If you enter a passphrase with special  symbols,  the  passphrase  can
       change  depending  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 to that, the cryptsetup FAQ describes
       several options.


       The following are valid actions for all supported device types.

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

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

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

              For backward compatibility there are open command aliases:

              create: open --type plain <device> <name> switched arguments)
              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.

       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).

       status <name>

              Reports the status for the mapping <name>.

       resize <name>

              Resizes an active mapping <name>.

              If --size (in sectors) is not specified, the size of the underlying block device 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.


       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 (created), 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)

              Creates a mapping with <name> backed by device <device>.

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

              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,  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.

       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 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 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.

              <options> can be [--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].

              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.  If the passphrase is not supplied via
              --key-file, the command prompts for it interactively.

              The  <device>  parameter  can  be  also  specified  by  LUKS  UUID  in  the  format
              UUID=<uuid>, which uses the symlinks in /dev/disk/by-uuid.

              <options> can be [--key-file, --keyfile-offset, --keyfile-size, --readonly, --test-
              passphrase, --allow-discards, --header, --key-slot, --master-key-file].

       luksSuspend <name>

              Suspends an active device (all IO operations  will  blocked  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].

       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]

       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.

              <options> can  be  [--key-file,  --keyfile-offset,  --keyfile-size,  --new-keyfile-
              offset, --new-keyfile-size, --key-slot, --master-key-file].

       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 positional argument or via --key-file.

              <options> can be [--key-file, --keyfile-offset, --keyfile-size]

              WARNING: If you read the passphrase from stdin (without further  argument  or  with
              '-' as argument to --key-file), batch-mode (-q) will be implicitely 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

       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].

       luksKillSlot <device> <key slot number>

              Wipe the key-slot number <key slot> from the LUKS device.  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].

              WARNING:  If  you  read the passphrase from stdin (without further argument or with
              '-' as argument to --key-file), batch-mode (-q) will be implicitely 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

       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.

       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. Beware that the master key cannot be changed 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.

              In order 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].

              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
              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 afterwards.

              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.


       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>

              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,

       See also section 7 of the FAQ and  for  more  information
       regarding loop-AES.

TCRYPT (TrueCrypt-compatible) EXTENSION

       cryptsetup  supports  mapping  of  TrueCrypt  or tcplay 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

       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).

       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. Use the whole device not the system partition  as  the  device

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

       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, --readonly, --test-

              The keyfile parameter allows 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.

       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

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

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

       See also for more information regarding TrueCrypt.

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


       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.

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

       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].


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

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

       --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

              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 both plain dm-crypt and LUKS.

              For XTS mode (a possible future default), use "aes-xts-plain" or  better  "aes-xts-
              plain64" as cipher specification and 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. Ignores 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
              accepts key files.

       --keyfile-size, -l value
              Read a maximum of value bytes from the key file.  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
              accepts key files.

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

       --new-keyfile-size  value
              Read a maximum of value bytes when adding a  new  passphrase  from  key  file  with
              luksAddKey.  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.

              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.

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

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

              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


              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
              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>
              Force  the  size  of the underlying 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>
              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.

              This is different from the --offset options with respect to the sector numbers used
              in  IV  calculation.   Using  --offset  will  shift  the IV calculation by the same
              negative amount.  Hence, if --offset n, sector n will get a sector number of 0  for
              the  IV  calculation.   Using --skip causes sector n to also be the first sector of
              the mapped device, but with its number for IV generation is n.

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

              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.

       --iter-time, -i <number of milliseconds>
              The number of milliseconds to spend with PBKDF2 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

       --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.

       --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

              If  not specified, cryptsetup tries to use the topology info provided by kernel for
              the underlying  device  to  get  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.

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

              The   UUID   must   be   provided   in   the    standard    UUID    format,    e.g.

              Allow  the use of discard (TRIM) requests for 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 no
              use it.

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

              Do  not  activate 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 options allows 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 argument to --header, it has  to  exist  and  be
              large  enough  to  contain the LUKS header.  See the cryptsetup FAQ for header size

              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.

              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 manual page for pwquality.conf(5).

              Show the program version.

              Show short option help.

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


       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.


       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

       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 has 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
       has  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

       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 binary  key.   if  the  key  file  is  shorter  than  the  key,
       cryptsetup will quit with an error.


       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  second  is  sufficient  for most practical cases. The only
       exception is a low-entropy passphrase used on a slow device.


       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.


       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


       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.


       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


       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 last close automatically). Of
       course, you can always map a file to a loop-device manually. See the cryptsetup FAQ for an

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


       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.


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


       cryptsetup originally written by Christophe Saout <>
       The   LUKS   extensions   and   original  man  page  were  written  by  Clemens  Fruhwirth
       Man page extensions by Milan Broz <>.
       Man page rewrite and extension by Arno Wagner <>.


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

       This is free software; see the source for copying conditions.  There is NO  warranty;  not


       The LUKS website at

       The   cryptsetup   FAQ,   contained   in   the   distribution   package   and   online  at

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

       The       LUKS       on-disk        format        specification        available        at