Provided by: gpg-agent_2.4.4-2ubuntu18_amd64 bug

NAME

       gpg-agent - Secret key management for GnuPG

SYNOPSIS

       gpg-agent [--homedir dir] [--options file] [options]
       gpg-agent [--homedir dir] [--options file] [options] --server
       gpg-agent [--homedir dir] [--options file] [options] --daemon [command_line]

DESCRIPTION

       gpg-agent is a daemon to manage secret (private) keys independently from any protocol.  It
       is used as a backend for gpg and gpgsm as well as for a couple of other utilities.

       The agent is automatically started on demand by gpg, gpgsm, gpgconf, or gpg-connect-agent.
       Thus there is no reason to start it manually.  In case you want to use the included Secure
       Shell Agent you may start the agent using:

         gpg-connect-agent /bye

       If you want to manually terminate the currently-running agent, you can safely do so with:

         gpgconf --kill gpg-agent

       You should always add the following lines to your .bashrc or whatever initialization  file
       is used for all shell invocations:

         GPG_TTY=$(tty)
         export GPG_TTY

       It  is  important  that  this  environment  variable always reflects the output of the tty
       command.  For W32 systems this option is not required.

       Please make sure that a proper pinentry program  has  been  installed  under  the  default
       filename  (which  is  system  dependent) or use the option pinentry-program to specify the
       full name of that program.  It is often useful to install a symbolic link from the  actual
       used    pinentry    (e.g.    ‘/usr/bin/pinentry-gtk’)    to   the   expected   one   (e.g.
       ‘/usr/bin/pinentry’).

COMMANDS

       Commands are not distinguished from options except for the fact that only one  command  is
       allowed.

       --version
              Print  the  program  version  and  licensing  information.   Note  that  you cannot
              abbreviate this command.

       --help
       -h     Print a usage message summarizing the most useful command-line options.  Note  that
              you cannot abbreviate this command.

       --dump-options
              Print  a  list  of  all  available  options  and  commands.   Note  that you cannot
              abbreviate this command.

       --server
              Run in server mode and wait for commands on the stdin.   The  default  mode  is  to
              create a socket and listen for commands there.

       --daemon [command line]
              Start  the gpg-agent as a daemon; that is, detach it from the console and run it in
              the background.

              As an alternative you may create a new process as a child of  gpg-agent:  gpg-agent
              --daemon  /bin/sh.   This  way  you  get  a  new  shell  with the environment setup
              properly; after you exit  from  this  shell,  gpg-agent  terminates  within  a  few
              seconds.

       --supervised
              Run in the foreground, sending logs by default to stderr, and listening on provided
              file descriptors, which must already be bound to listening sockets.  This option is
              deprecated and not supported on Windows.

              If  in  ‘common.conf’  the  option  no-autostart is set, any start attempts will be
              ignored.

              In --supervised mode, different  file  descriptors  can  be  provided  for  use  as
              different  socket  types  (e.g.  ssh,  extra) as long as they are identified in the
              environment  variable  LISTEN_FDNAMES   (see   sd_listen_fds(3)   on   some   Linux
              distributions for more information on this convention).

OPTIONS

       Options  may  either  be  used on the command line or, after stripping off the two leading
       dashes, in the configuration file.

       --options file
              Reads configuration from file instead of from the  default  per-user  configuration
              file.  The default configuration file is named ‘gpg-agent.conf’ and expected in the
              ‘.gnupg’ directory directly below the home directory of the user.  This  option  is
              ignored if used in an options file.

       --homedir dir
              Set  the  name  of  the home directory to dir. If this option is not used, the home
              directory defaults to ‘~/.gnupg’.  It is only recognized when given on the  command
              line.  It also overrides any home directory stated through the environment variable
              ‘GNUPGHOME’  or  (on  Windows   systems)   by   means   of   the   Registry   entry
              HKCU\Software\GNU\GnuPG:HomeDir.

              On  Windows  systems it is possible to install GnuPG as a portable application.  In
              this case only this command line option is considered, all other ways to set a home
              directory are ignored.

       -v
       --verbose
              Outputs  additional  information  while running.  You can increase the verbosity by
              giving several verbose commands to gpg-agent, such as ‘-vv’.

       -q
       --quiet
              Try to be as quiet as possible.

       --batch
              Don't invoke a pinentry or do any other thing requiring human interaction.

       --faked-system-time epoch
              This option is only useful for testing; it sets the system time back  or  forth  to
              epoch which is the number of seconds elapsed since the year 1970.

       --debug-level level
              Select  the debug level for investigating problems. level may be a numeric value or
              a keyword:

              none   No debugging at all.  A value of less than 1 may  be  used  instead  of  the
                     keyword.

              basic  Some  basic  debug messages.  A value between 1 and 2 may be used instead of
                     the keyword.

              advanced
                     More verbose debug messages.  A value between 3 and 5 may be used instead of
                     the keyword.

              expert Even more detailed messages.  A value between 6 and 8 may be used instead of
                     the keyword.

              guru   All of the debug messages you can get. A value greater than 8  may  be  used
                     instead  of the keyword.  The creation of hash tracing files is only enabled
                     if the keyword is used.

       How these messages are mapped to the actual debugging  flags  is  not  specified  and  may
       change  with  newer  releases of this program. They are however carefully selected to best
       aid in debugging.

       --debug flags
              Set debug flags.  All flags are or-ed and flags may be  given  in  C  syntax  (e.g.
              0x0042) or as a comma separated list of flag names.  To get a list of all supported
              flags the single word "help" can be used. This option is only useful for  debugging
              and the behavior may change at any time without notice.

       --debug-all
              Same as --debug=0xffffffff

       --debug-wait n
              When  running  in server mode, wait n seconds before entering the actual processing
              loop and print the pid.  This gives time to attach a debugger.

       --debug-quick-random
              This option inhibits the use of the very secure random quality  level  (Libgcrypt’s
              GCRY_VERY_STRONG_RANDOM)  and degrades all request down to standard random quality.
              It is only used for testing and should not be used for any production quality keys.
              This option is only effective when given on the command line.

              On  GNU/Linux, another way to quickly generate insecure keys is to use rngd to fill
              the kernel's entropy pool with  lower  quality  random  data.   rngd  is  typically
              provided  by  the  rng-tools  package.   It can be run as follows: ‘sudo rngd -f -r
              /dev/urandom’.

       --debug-pinentry
              This option enables extra debug information pertaining to the Pinentry.  As of  now
              it is only useful when used along with --debug 1024.

       --no-detach
              Don't detach the process from the console.  This is mainly useful for debugging.

       --steal-socket
              In --daemon mode, gpg-agent detects an already running gpg-agent and does not allow
              one to start a new instance. This option can be used to override  this  check:  the
              new  gpg-agent  process  will  try  to take over the communication sockets from the
              already running process and start anyway.  This option should  in  general  not  be
              used.

       -s
       --sh
       -c
       --csh  Format the info output in daemon mode for use with the standard Bourne shell or the
              C-shell respectively.  The default is to guess it based on the environment variable
              SHELL which is correct in almost all cases.

       --grab
       --no-grab
              Tell the pinentry to grab the keyboard and mouse.  This option should be used on X-
              Servers to avoid X-sniffing attacks. Any use of the option --grab overrides an used
              option --no-grab.  The default is --no-grab.

       --log-file file
              Append  all  logging output to file.  This is very helpful in seeing what the agent
              actually does. Use ‘socket://’ to log to socket.  If neither a log file nor  a  log
              file   descriptor   has  been  set  on  a  Windows  platform,  the  Registry  entry
              HKCU\Software\GNU\GnuPG:DefaultLogFile, if set, is  used  to  specify  the  logging
              output.

       --no-allow-mark-trusted
              Do   not   allow  clients  to  mark  keys  as  trusted,  i.e.  put  them  into  the
              ‘trustlist.txt’ file.  This makes it harder for users to inadvertently accept Root-
              CA keys.

       --no-user-trustlist
              Entirely  ignore  the  user  trust  list  and  consider  only  the global trustlist
              (‘/etc/gnupg/trustlist.txt’).  This implies the [option --no-allow-mark-trusted].

       --sys-trustlist-name file
              Changes the default name for the global trustlist from "trustlist.txt" to file.  If
              file  does  not  contain any slashes and does not start with "~/" it is searched in
              the system configuration directory (‘/etc/gnupg’).

       --allow-preset-passphrase
              This option allows the use of gpg-preset-passphrase to seed the internal  cache  of
              gpg-agent with passphrases.

       --no-allow-loopback-pinentry

       --allow-loopback-pinentry
              Disallow  or  allow  clients  to use the loopback pinentry features; see the option
              pinentry-mode for details.  Allow is the default.

              The --force option of the Assuan command DELETE_KEY  is  also  controlled  by  this
              option: The option is ignored if a loopback pinentry is disallowed.

       --no-allow-external-cache
              Tell Pinentry not to enable features which use an external cache for passphrases.

              Some desktop environments prefer to unlock all credentials with one master password
              and may have installed a Pinentry which employs an  additional  external  cache  to
              implement  such a policy.  By using this option the Pinentry is advised not to make
              use of such a cache and instead always ask the user for the requested passphrase.

       --allow-emacs-pinentry
              Tell Pinentry to allow features to divert the passphrase entry to a  running  Emacs
              instance.  How this is exactly handled depends on the version of the used Pinentry.

       --ignore-cache-for-signing
              This  option  will  let  gpg-agent  bypass  the  passphrase  cache  for all signing
              operation.  Note that there is also a per-session option to control  this  behavior
              but this command line option takes precedence.

       --default-cache-ttl n
              Set  the  time  a  cache  entry is valid to n seconds.  The default is 600 seconds.
              Each time a cache entry is accessed, the entry's timer is reset.  To set an entry's
              maximum  lifetime,  use  max-cache-ttl.   Note  that a cached passphrase may not be
              evicted immediately from memory if no client requests a cache operation.   This  is
              due to an internal housekeeping function which is only run every few seconds.

       --default-cache-ttl-ssh n
              Set the time a cache entry used for SSH keys is valid to n seconds.  The default is
              1800 seconds.  Each time a cache entry is accessed, the entry's timer is reset.  To
              set an entry's maximum lifetime, use max-cache-ttl-ssh.

       --max-cache-ttl n
              Set  the maximum time a cache entry is valid to n seconds.  After this time a cache
              entry will be expired even if it has been accessed recently or has been  set  using
              gpg-preset-passphrase.  The default is 2 hours (7200 seconds).

       --max-cache-ttl-ssh n
              Set  the maximum time a cache entry used for SSH keys is valid to n seconds.  After
              this time a cache entry will be expired even if it has been  accessed  recently  or
              has been set using gpg-preset-passphrase.  The default is 2 hours (7200 seconds).

       --enforce-passphrase-constraints
              Enforce  the  passphrase  constraints by not allowing the user to bypass them using
              the ``Take it anyway'' button.

       --min-passphrase-len n
              Set the minimal length of a passphrase.  When entering  a  new  passphrase  shorter
              than this value a warning will be displayed.  Defaults to 8.

       --min-passphrase-nonalpha n
              Set  the  minimal  number of digits or special characters required in a passphrase.
              When entering a new passphrase with less than this  number  of  digits  or  special
              characters a warning will be displayed.  Defaults to 1.

       --check-passphrase-pattern file
       --check-sym-passphrase-pattern file
              Check  the  passphrase  against  the  pattern  given  in file.  When entering a new
              passphrase matching one of these pattern a warning will be displayed.  If file does
              not  contain  any slashes and does not start with "~/" it is searched in the system
              configuration directory (‘/etc/gnupg’).  The default is  not  to  use  any  pattern
              file.  The second version of this option is only used when creating a new symmetric
              key to allow the use of different patterns for such passphrases.

              Security note: It is known that checking a passphrase against a list of pattern  or
              even  against  a  complete  dictionary  is  not  very  effective  to  enforce  good
              passphrases.  Users will soon figure up ways to bypass such  a  policy.   A  better
              policy  is  to  educate  users  on  good  security behavior and optionally to run a
              passphrase cracker regularly on all users passphrases  to  catch  the  very  simple
              ones.

       --max-passphrase-days n
              Ask  the user to change the passphrase if n days have passed since the last change.
              With --enforce-passphrase-constraints set the user may not bypass this check.

       --enable-passphrase-history
              This option does nothing yet.

       --pinentry-invisible-char char
              This option asks the Pinentry to use char for displaying hidden  characters.   char
              must be one character UTF-8 string.  A Pinentry may or may not honor this request.

       --pinentry-timeout n
              This  option  asks the Pinentry to timeout after n seconds with no user input.  The
              default value of 0 does not ask the pinentry to timeout, however a Pinentry may use
              its  own  default timeout value in this case.  A Pinentry may or may not honor this
              request.

       --pinentry-formatted-passphrase
              This option asks the Pinentry to enable passphrase formatting when asking the  user
              for a new passphrase and masking of the passphrase is turned off.

              If  passphrase  formatting  is  enabled, then all non-breaking space characters are
              stripped from the entered passphrase.  Passphrase formatting is  mostly  useful  in
              combination  with passphrases generated with the GENPIN feature of some Pinentries.
              Note that such a generated passphrase, if not  modified  by  the  user,  skips  all
              passphrase  constraints checking because such constraints would actually weaken the
              generated passphrase.

       --pinentry-program filename
              Use program filename as the PIN entry.   The  default  is  installation  dependent.
              With  the  default configuration the name of the default pinentry is ‘pinentry’; if
              that file does not exist but a ‘pinentry-basic’ exist the latter is used.

              On a Windows platform the default is to use the first existing  program  from  this
              list: ‘bin\pinentry.exe’, ‘..\Gpg4win\bin\pinentry.exe’, ‘..\Gpg4win\pinentry.exe’,
              ‘..\GNU\GnuPG\pinentry.exe’,  ‘..\GNU\bin\pinentry.exe’,   ‘bin\pinentry-basic.exe’
              where the file names are relative to the GnuPG installation directory.

       --pinentry-touch-file filename
              By default the filename of the socket gpg-agent is listening for requests is passed
              to Pinentry, so that it can touch that file before exiting (it does  this  only  in
              curses  mode).   This  option changes the file passed to Pinentry to filename.  The
              special name /dev/null may be used to completely disable this feature.   Note  that
              Pinentry will not create that file, it will only change the modification and access
              time.

       --scdaemon-program filename
              Use program  filename  as  the  Smartcard  daemon.   The  default  is  installation
              dependent and can be shown with the gpgconf command.

       --disable-scdaemon
              Do  not make use of the scdaemon tool.  This option has the effect of disabling the
              ability to do smartcard operations.  Note, that enabling  this  option  at  runtime
              does not kill an already forked scdaemon.

       --disable-check-own-socket
              gpg-agent  employs  a  periodic  self-test to detect a stolen socket.  This usually
              means a second instance of gpg-agent has taken over the socket and  gpg-agent  will
              then  terminate  itself.   This  option  may  be used to disable this self-test for
              debugging purposes.

       --use-standard-socket
       --no-use-standard-socket
       --use-standard-socket-p
              Since GnuPG 2.1 the standard socket is always used.  These  options  have  no  more
              effect.   The  command  gpg-agent  --use-standard-socket-p  will thus always return
              success.

       --display string
       --ttyname string
       --ttytype string
       --lc-ctype string
       --lc-messages string
       --xauthority string
              These options are used with the server mode to pass localization information.

       --keep-tty
       --keep-display
              Ignore requests to change the current tty or X  window  system's  DISPLAY  variable
              respectively.   This is useful to lock the pinentry to pop up at the tty or display
              you started the agent.

       --listen-backlog n
              Set the size of the queue for pending connections.  The default is 64.

       --extra-socket name
              The extra socket is created by default, you may use this option to change the  name
              of the socket.  To disable the creation of the socket use ``none'' or ``/dev/null''
              for name.

              Also listen on native gpg-agent connections on the given socket.  The intended  use
              for  this  extra  socket  is to setup a Unix domain socket forwarding from a remote
              machine to this socket on the local machine.  A gpg running on the  remote  machine
              may  then  connect  to  the local gpg-agent and use its private keys.  This enables
              decrypting or signing data on a remote machine without exposing the private keys to
              the remote machine.

       --enable-extended-key-format
       --disable-extended-key-format
              These options are obsolete and have no effect.  The extended key format is used for
              years now and has been supported since 2.1.12.  Existing keys in the old format are
              migrated to the new format as soon as they are touched.

       --enable-ssh-support
       --enable-win32-openssh-support
       --enable-putty-support

              On  Unix platforms the OpenSSH Agent protocol is always enabled, but gpg-agent will
              only set the SSH_AUTH_SOCK variable if  the  option  enable-ssh-support  is  given.
              Some  Linux distributions use the presence of this option to decide whether the old
              ssh-agent shall be started.

              On Windows support for the native ssh implementation must be enabled using the  the
              option  enable-win32-openssh-support.   For  using  gpg-agent  as a replacement for
              PuTTY's Pageant, the option enable-putty-support must be enabled.

              In this mode of  operation,  the  agent  does  not  only  implement  the  gpg-agent
              protocol, but also the agent protocol used by OpenSSH (through a separate socket or
              via Named Pipes) or the protocol used by PuTTY.  Consequently, this allows  one  to
              use the gpg-agent as a drop-in replacement for the ssh-agent.

              SSH keys, which are to be used through the agent, need to be added to the gpg-agent
              initially through the ssh-add utility.  When a key is added, ssh-add will  ask  for
              the  password of the provided key file and send the unprotected key material to the
              agent; this causes the gpg-agent to ask for a passphrase, which is to be  used  for
              encrypting the newly received key and storing it in a gpg-agent specific directory.

              Once a key has been added to the gpg-agent this way, the gpg-agent will be ready to
              use the key.

              Note: in case the gpg-agent receives a signature request, the user might need to be
              prompted for a passphrase, which is necessary for decrypting the stored key.  Since
              the ssh-agent protocol does not contain a mechanism for telling the agent on  which
              display/terminal  it  is  running,  gpg-agent's  ssh-support  will use the TTY or X
              display where gpg-agent has been started.  To switch this display  to  the  current
              one, the following command may be used:

         gpg-connect-agent updatestartuptty /bye

       Although  all  GnuPG components try to start the gpg-agent as needed, this is not possible
       for the ssh support because ssh does not know about it.   Thus  if  no  GnuPG  tool  which
       accesses  the  agent has been run, there is no guarantee that ssh is able to use gpg-agent
       for authentication.  To fix this you may start  gpg-agent  if  needed  using  this  simple
       command:

         gpg-connect-agent /bye

       Adding the --verbose shows the progress of starting the agent.

       The --enable-putty-support is only available under Windows and allows the use of gpg-agent
       with the ssh implementation putty.  This is similar to the regular ssh-agent  support  but
       makes use of Windows message queue as required by putty.

       The order in which keys are presented to ssh are:

              Negative Use-for-ssh values
                           If a key file has the attribute "Use-for-ssh" and its value is
                           negative, these keys are presented first to ssh.  The negative
                           values are capped at -999 with -999 being lower ranked than -1.
                           These values can be used to prefer on-disk keys over keys taken
                           from active cards.

              Active cards
                           Active cards (inserted into a card reader or plugged in tokens)
                           are always tried; they are ordered by their serial numbers.

              Keys listed in the sshcontrol file
                           Non-disabled keys from the sshcontrol file are presented in the
                           order they appear in this file.  Note that the sshcontrol file
                           is deprecated.

              Positive Use-for-ssh values
                           If a key file has the attribute "Use-for-ssh" and its value is
                           "yes", "true", or any positive number the key is presented in
                           the order of their values.  "yes" and "true" have a value of 1;
                           other values are capped at 99999.

       Editing the "Use-for-ssh" values can be done with an editor or using gpg-connect-agent and
       "KEYATTR" (Remember to append a colon to the key; i.e. use "Use-for-ssh:").

       --ssh-fingerprint-digest

              Select the digest algorithm used to compute ssh fingerprints that are  communicated
              to  the user, e.g. in pinentry dialogs.  OpenSSH has transitioned from using MD5 to
              the more secure SHA256.

       --auto-expand-secmem n
              Allow Libgcrypt to expand its secure memory area as required.  The optional value n
              is  a  non-negative  integer  with  a  suggested size in bytes of each additionally
              allocated secure memory area.  The value is rounded up to the next 32 KiB; usual  C
              style  prefixes  are  allowed.   For an heavy loaded gpg-agent with many concurrent
              connection this option avoids sign or decrypt errors due to out  of  secure  memory
              error returns.

       --s2k-calibration milliseconds
              Change  the default calibration time to milliseconds.  The given value is capped at
              60 seconds; a value of 0 resets to the compiled-in default.  This option is re-read
              on  a  SIGHUP  (or  gpgconf  --reload  gpg-agent)  and  the  S2K  count is then re-
              calibrated.

       --s2k-count n
              Specify the iteration count used to protect the passphrase.   This  option  can  be
              used  to  override  the  auto-calibration  done  by  default.  The auto-calibration
              computes a count which requires by default 100ms to mangle a given passphrase.  See
              also --s2k-calibration.

              To  view the actually used iteration count and the milliseconds required for an S2K
              operation use:

         gpg-connect-agent 'GETINFO s2k_count' /bye
         gpg-connect-agent 'GETINFO s2k_time' /bye

       To view the auto-calibrated count use:

         gpg-connect-agent 'GETINFO s2k_count_cal' /bye

EXAMPLES

       It is important to set the environment variable GPG_TTY in your login shell,  for  example
       in the ‘~/.bashrc’ init script:

           export GPG_TTY=$(tty)

       If you enabled the Ssh Agent Support, you also need to tell ssh about it by adding this to
       your init script:

         unset SSH_AGENT_PID
         if [ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne $$ ]; then
           export SSH_AUTH_SOCK="$(gpgconf --list-dirs agent-ssh-socket)"
         fi

FILES

       There are a few configuration files needed for the operation of the agent. By default they
       may all be found in the current home directory (see: [option --homedir]).

       gpg-agent.conf
                This is the standard configuration file read by gpg-agent on
                startup.  It may contain any valid long option; the leading
                two dashes may not be entered and the option may not be abbreviated.
                This file is also read after a SIGHUP however only a few
                options will actually have an effect.  This default name may be
                changed on the command line (see: [option --options]).
                You should backup this file.

       trustlist.txt
                This is the list of trusted keys.  You should backup this file.

                Comment lines, indicated by a leading hash mark, as well as empty
                lines are ignored.  To mark a key as trusted you need to enter its
                fingerprint followed by a space and a capital letter S.  Colons
                may optionally be used to separate the bytes of a fingerprint; this
                enables cutting and pasting the fingerprint from a key listing output.  If
                the line is prefixed with a ! the key is explicitly marked as
                not trusted.

                Here is an example where two keys are marked as ultimately trusted
                and one as not trusted:

                  .RS 2
                # CN=Wurzel ZS 3,O=Intevation GmbH,C=DE
                A6935DD34EF3087973C706FC311AA2CCF733765B S

                # CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE
                DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S

                # CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE
                !14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S
                .fi

       Before entering a key into this file, you need to ensure its
       authenticity.  How to do this depends on your organisation; your
       administrator might have already entered those keys which are deemed
       trustworthy enough into this file.  Places where to look for the
       fingerprint of a root certificate are letters received from the CA or
       the website of the CA (after making 100% sure that this is indeed the
       website of that CA).  You may want to consider disallowing interactive
       updates of this file by using the [option --no-allow-mark-trusted].
       It might even be advisable to change the permissions to read-only so
       that this file can't be changed inadvertently.

       As a special feature a line include-default will include a global
       list of trusted certificates (e.g. ‘/etc/gnupg/trustlist.txt’).
       This global list is also used if the local list is not available;
       the [option --no-user-trustlist] enforces the use of only
       this global list.

       It is possible to add further flags after the S for use by the
       caller:

              relax  Relax checking of some root certificate requirements.  As of now this
                     flag allows the use of root certificates with a missing basicConstraints
                     attribute (despite that it is a MUST for CA certificates) and disables
                     CRL checking for the root certificate.

              cm     If validation of a certificate finally issued by a CA with this flag set
                     fails, try again using the chain validation model.

              qual   The CA is allowed to issue certificates for qualified signatures.
                     This flag has an effect only if used in the global list.  This is now
                     the preferred way to mark such CA; the old way of having a separate
                     file ‘qualified.txt’ is still supported.

              de-vs  The CA is part of an approved PKI for the German classification level
                     VS-NfD.  It is only valid in the global trustlist.  As of now this is
                     used only for documentation purpose.

       sshcontrol
              This file is used when support for the secure shell agent protocol has
              been enabled (see: [option --enable-ssh-support]). Only keys present in
              this file are used in the SSH protocol.  You should backup this file.

              This file is deprecated in favor of the "Use-for-ssh" attribute in the
              key files.

              The ssh-add tool may be used to add new entries to this file;
              you may also add them manually.  Comment lines, indicated by a leading
              hash mark, as well as empty lines are ignored.  An entry starts with
              optional whitespace, followed by the keygrip of the key given as 40 hex
              digits, optionally followed by the caching TTL in seconds and another
              optional field for arbitrary flags.  A non-zero TTL overrides the global
              default as set by --default-cache-ttl-ssh.

              The only flag support is confirm.  If this flag is found for a
              key, each use of the key will pop up a pinentry to confirm the use of
              that key.  The flag is automatically set if a new key was loaded into
              gpg-agent using the option -c of the ssh-add
              command.

              The keygrip may be prefixed with a ! to disable an entry.

              The following example lists exactly one key.  Note that keys available
              through a OpenPGP smartcard in the active smartcard reader are
              implicitly added to this list; i.e. there is no need to list them.

                # Key added on: 2011-07-20 20:38:46
                # Fingerprint:  5e:8d:c4:ad:e7:af:6e:27:8a:d6:13:e4:79:ad:0b:81
                34B62F25E277CF13D3C6BCEBFD3F85D08F0A864B 0 confirm

       private-keys-v1.d/

                This is the directory where gpg-agent stores the private keys.  Each
                key is stored in a file with the name made up of the keygrip and the
                suffix ‘key’.  You should backup all files in this directory
                and take great care to keep this backup closed away.

       Note that on larger installations, it is useful to put predefined files into the directory
       ‘/etc/skel/.gnupg’ so that newly created users start up with a working configuration.  For
       existing  users  the  a  small  helper  script  is  provided  to  create these files (see:
       [addgnupghome]).

SIGNALS

       A running gpg-agent may be controlled by signals, i.e. using the kill command  to  send  a
       signal to the process.

       Here is a list of supported signals:

       SIGHUP This signal flushes all cached passphrases and if the program has been started with
              a configuration file, the configuration file is read again.  Only  certain  options
              are   honored:  quiet,  verbose,  debug,  debug-all,  debug-level,  debug-pinentry,
              no-grab,     pinentry-program,     pinentry-invisible-char,      default-cache-ttl,
              max-cache-ttl,    ignore-cache-for-signing,   s2k-count,   no-allow-external-cache,
              allow-emacs-pinentry,      no-allow-mark-trusted,       disable-scdaemon,       and
              disable-check-own-socket.   scdaemon-program  is  also  supported  but  due  to the
              current implementation, which calls the scdaemon only once, it is not of  much  use
              unless you manually kill the scdaemon.

       SIGTERM
              Shuts  down the process but waits until all current requests are fulfilled.  If the
              process has received 3 of these signals and requests are still pending, a  shutdown
              is forced.

       SIGINT Shuts down the process immediately.

       SIGUSR1
              Dump internal information to the log file.

       SIGUSR2
              This signal is used for internal purposes.

SEE ALSO

       gpg(1), gpgsm(1), gpgconf(1), gpg-connect-agent(1), scdaemon(1)

       The  full documentation for this tool is maintained as a Texinfo manual.  If GnuPG and the
       info program are properly installed at your site, the command

         info gnupg

       should give you access to the complete manual including a menu structure and an index.