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2.2 Option Summary

--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.

--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.

To install GnuPG as a portable application under Windows, create an empty file name gpgconf.ctl in the same directory as the tool gpgconf.exe. The root of the installation is than that directory; or, if gpgconf.exe has been installed directly below a directory named bin, its parent directory. You also need to make sure that the following directories exist and are writable: ROOT/home for the GnuPG home and ROOT/usr/local/var/cache/gnupg for internal cache files.

Outputs additional information while running. You can increase the verbosity by giving several verbose commands to gpgsm, such as ‘-vv’.
Try to be as quiet as possible.
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:
No debugging at all. A value of less than 1 may be used instead of the keyword.
Some basic debug messages. A value between 1 and 2 may be used instead of the keyword.
More verbose debug messages. A value between 3 and 5 may be used instead of the keyword.
Even more detailed messages. A value between 6 and 8 may be used instead of the keyword.
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
This option is only useful for debugging and the behaviour may change at any time without notice. FLAGS are bit encoded and may be given in usual C-Syntax. The currently defined bits are:
0 (1)
X.509 or OpenPGP protocol related data
1 (2)
values of big number integers
2 (4)
low level crypto operations
5 (32)
memory allocation
6 (64)
7 (128)
show memory statistics.
9 (512)
write hashed data to files named dbgmd-000*
10 (1024)
trace Assuan protocol
12 (4096)
bypass all certificate validation

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.
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 shall not be used for any production quality keys. This option is only effective when given on the command line.
This option enables extra debug information pertaining to the Pinentry. As of now it is only useful when used along with --debug 1024.
Don't detach the process from the console. This is mainly useful for debugging.
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.
Tell the pinentry not to grab the keyboard and mouse. This option should in general not be used to avoid X-sniffing attacks.

--log-file file
Append all logging output to file. This is very helpful in seeing what the agent actually does. 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.

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.

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

Allow clients to use the loopback pinentry features; see the option pinentry-mode for details.
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.

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.
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 behaviour 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.
--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 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 the passphrase against the pattern given in file. When entering a new passphrase matching one of these pattern a warning will be displayed. file should be an absolute filename. The default is not to use any pattern file.

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.
This option does nothing yet.
--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.
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.
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.
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.
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.

--extra-socket 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 allows to decrypt or sign data on a remote machine without exposing the private keys to the remote machine.

Enable the OpenSSH Agent protocol.

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). Consequently, it should be possible to use the gpg-agent as a drop-in replacement for the well known 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.

All the long options may also be given in the configuration file after stripping off the two leading dashes.