Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm a little confused on how to run unison to sync files with group and owner attributes on an ubuntu system, as you need to be root. But I need to do this remotely and automated. I know I can set up ssh keys and the such for my user but that doesn't matter because I still wont be able to ssh as root to do the changes on the remote system.

I guess my question is; How would I go about using root on the remote system for unison? or is there a way of setting a command for a user to 'auto-run' as root without password?

Or are there any other ways that I could do this?

Any guidance with this is appreciated.

share|improve this question
up vote 1 down vote accepted

You should be able to setup ssh login with keys as you have stated.

Make sure your sshd_config allows root logins

PermitRootLogin without-password

Then copy the generated public-key to /root/.ssh/authorized_keys.

You should be able to login now, just tell unison to use the ssh key you generated.

share|improve this answer
With this would I have to enable root account? – Elgoog Dec 18 '11 at 0:46
Yes, you should have an enabled and working root account. The options for 'PermitRootLogin' are 'no', 'yes', and 'without-password'. The last one allowing only logins using ssh-keys. – Sig-IO Dec 18 '11 at 0:51
works like a charm, I never knew about the without-password so thank you! – Elgoog Dec 18 '11 at 1:01

Sudo can be configured to avoid asking for a password on some or all commands with the NOPASSWD parameter; but in any case I think it would be simpler to use ssh keys to access the remote system directly as root; after setting up passwordless authentication, unison should be called as follows:

unison a.tmp ssh://username@remotehostname/a.tmp
share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.