keychain - re-use ssh-agent and/or gpg-agent between logins

keychain [ -hkQqV ] [ --clear --help --ignore-missing --noask --nocolor --nogui --nolock --stop --quick --quiet --version ] [ --agents list ] [ --attempts num ] [ --dir dirname ] [ --host name ] [ --lockwait seconds ] [ --timeout minutes ] [ keys... ]

keychain is a manager for ssh-agent, typically run from ~/.bash_profile. It allows your shells and cron jobs to share a single ssh-agent process. By default, the ssh-agent started by keychain is long-running and will continue to run, even after you have logged out from the system. If you want to change this behavior, take a look at the --clear and --timeout options, described below.

When keychain is run, it checks for a running ssh-agent, otherwise it starts one. It saves the ssh-agent environment variables to ~/.keychain/${HOSTNAME}-sh, so that subsequent logins and non-interactive shells such as cron jobs can source the file and make passwordless ssh connections. In addition, when keychain runs, it verifies that the key files specified on the command-line are known to ssh-agent, otherwise it loads them, prompting you for a password if necessary.

Keychain also supports gpg-agent. It does not track keys since that ability is not available in current versions of gpg-agent. It simply will start gpg-agent and make it available to following logins.

keychain supports most UNIX-like operating systems, including Cygwin. It works with both Bourne-compatible and csh-compatible shells.

--agents list

Start the agents listed. By default keychain will build the list automatically based on the existence of ssh-agent and/or gpg-agent on the system. The list should be comma-separated, for example "gpg,ssh"

--attempts num

Try num times to add keys before giving up. The default is 3.

--clear

Delete all of ssh-agent's keys. Typically this is used in .bash_profile. The theory behind this is that keychain should assume that you are an intruder until proven otherwise. However, while this option increases security, it still allows your cron jobs to use your ssh keys when you're logged out.

--dir dirname

Keychain will use dirname rather than $HOME/.keychain

-h --help

Show help that looks remarkably like this man-page.

--host name

Set alternate hostname for creation of pidfiles

--ignore-missing

Don't warn if some keys on the command-line can't be found. This is useful for situations where you have a shared .bash_profile, but your keys might not be available on every machine where keychain is run.

--lockwait seconds

How long to wait for the lock to become available. Defaults to 30 seconds.

--noask

This option tells keychain do everything it normally does (ensure ssh-agent is running, set up the ~/.keychain/[hostname]-{c}sh files) except that it will not prompt you to add any of the keys you specified if they haven't yet been added to ssh-agent.

--nocolor

Disable color hilighting for non ANSI-compatible terms.

--nogui

Don't honor SSH_ASKPASS, if it is set. This will cause ssh-add to prompt on the terminal instead of using a graphical program.

--nolock

Don't attempt to use a lockfile while manipulating files, pids and keys.

-k --stop

Stop all running ssh-agent processes.

-Q --quick

If an ssh-agent process is running then use it. Don't verify the list of keys, other than making sure it's non-empty. This option avoids locking when possible so that multiple terminals can be opened simultaneously without waiting on each other.

-q --quiet

Only print messages in case of warning, error or required interactivity.

--timeout minutes

Set a timeout in minutes on your keys. This is conveyed to ssh-agent which does the actual timing out of keys since keychain doesn't run continuously.

-V --version

Show version information.

This snippet would work in .bash_profile (for bash) or .zlogin (for zsh):

keychain id_rsa id_dsa
. ~/.keychain/$HOSTNAME-sh

This snippet would work in other Bourne-compatible shells:

keychain id_rsa id_dsa
. ~/.keychain/`uname -n`-sh

This snippet would work in .login (for csh or tcsh):

keychain id_rsa id_dsa
source $HOME/.keychain/`uname -n`-csh

ssh-agent(1)

Keychain is maintained by Aron Griffis <agriffis@gentoo.org>. If you need to report a bug or request an enhancement, please do so at http://bugs.gentoo.org/ and assign to agriffis@gentoo.org

Keychain was originally written by Daniel Robbins <drobbins@gentoo.org>, who has also written a series of three articles about it. The articles can be found starting at http://www-106.ibm.com/developerworks/library/l-keyc.html

Hey! The above document had some coding errors, which are explained below:

Around line 164:

'=end' without a target?