Ubuntu uses the gnome-keyring-daemon to manage ssh keys / passwords, with the seahorse front end (which in typical Ubuntu fashion it unhelpfully refers to as ‘Passwords and Keys’).
Reference: How can I permanently save a password-protected SSH key?
Decrypting ssh key in cron job
If you have an encrypted ssh key and you’d like to use ssh or rsync (via ssh) in a cron job, then you’ll need to set the SSH_AUTH_SOCK environment variable.
You can see what it is currently set to:
stephan@foopc:~ $ echo $SSH_AUTH_SOCK
/run/user/1004/keyring-jBLQpz/ssh
Note that the keyring-* file used to be in /tmp/ (as in the references below) but in Ubuntu 14.04 it is stored in the /run/user/[uid]/ directory.
While you could use this path in your cron script, it’s better to run a command to locate it (as it may change):
find /run/user/[uid]/keyring*/ -perm 0775 -type s -user [username] -group [groupname] -name '*ssh' | head -n 1
E.g:
stephan@foopc:~ $ find /run/user/1004/keyring*/ -perm 0775 -type s -user stephan -group stephan -name '*ssh' | head -n 1
/run/user/1004/keyring-jBLQpz/ssh
So in your cron job you’d call a script that does the following:
#!/bin/bash
export SSH_AUTH_SOCK=`find /run/user/1004/keyring*/ -perm 0775 -type s -user stephan -group stephan -name '*ssh' | head -n 1`
# Do stuff with ssh
rsync -avP -e 'ssh' --exclude=tmp example.com:/some/directory ~/backups/example
