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 usual way to run the agent is from the ~/.xsession file:
eval $(gpg-agent --daemon)
If you don't use an X server, you can also put this into your regular
startup file ~/.profile or .bash_profile. It is best not
to run multiple instance of the gpg-agent, so you should make
sure that only one is running: gpg-agent uses an environment
variable to inform clients about the communication parameters. You can
write the content of this environment variable to a file so that you can
test for a running agent. This short script may do the job:
if test -f $HOME/.gpg-agent-info && \
kill -0 $(cut -d: -f 2 $HOME/.gpg-agent-info) 2>/dev/null; then
GPG_AGENT_INFO=$(cat $HOME/.gpg-agent-info)
export GPG_AGENT_INFO
else
eval $(gpg-agent --daemon)
echo $GPG_AGENT_INFO >$HOME/.gpg-agent-info
fi
Note that the new option --write-env-file may be used instead.
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 dependant) 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).
See Option Index,for an index to GPG-AGENT's commands and options.