Logging onto a machine over ssh typically requires a password to be entered before access is granted. Alternatively, a key/certificate (without a passphrase) can be installed onto the remote machine so that logging on no longer requires a password. This is particularly useful for automated or scripted solutions.However, it is considered inadvisable and unsafe to create a key/certificate without a passphrase. Solutions involving ssh-add and ssh-agent are proposed as a means to enter a passphrase only once per session, but to still use a key/certificate with a passphrase.What is the solution for automated connections between machines? How can a machine automatically update from a remote Bazaar repository (via bzr+ssh?) on a regular basis, as in a cron job? How can a machine automatically backup data from another machine (via rsync) as part of a cron job? rsyncd? This would not be encrypted though, which is a major disadvantage. I haven't looked at Bazaar daemon/server options.
Automated ssh login with passphrase?
ssh;security;password;key authentication
For automated logins you have to use keyless ssh keys as you would have to manually intervene at the startup and provide a pass-phrase and have to resupply it after an restart.To secure such keys there are multiple solutions - see man sshd for more details:Restrict the remote host for the key with the from= parameter, e.g:from=*.example.com ssh_keythis will only allow machines from example.comSpecify which command will be executed with the command= parameter, e.g:command=some command ssh_keyUse a dedicated user with an restricted shell or only with the necessary permissions, e.g. for backup the user can only run rsync with sudo.