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I am setting up a backup server on which I want to run rsync over ssh to backup content on other servers every night. I would like to set up ssh keys to make it password-less, but I want to preserve ownership of files and permissions. There are a number of users on the server to be backed up which won't all exist on the backup server.

What would be the best way to do this? I guess the backup job will need to connect as root to , but I don't want to enable root ssh access on the servers.

thanks for any tips,


ps, all servers are running UBUNTU Server 12.04 LTS and are behind a university firewall.

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up vote 0 down vote accepted

You cannot. Linux REQUIRES you to have root access to save a file as any user other than yourself. The ONLY workaround is to tarball it and then transfer the tarball to the server.

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As a side note, you can enable root access over ssh on the server so long as you set authorized_keys to only allow a specific command (rsync in this case). Use the command option in authorized_keys to set a specific key to only allow a specific command such as /usr/bin/rsync. However, due to the security of ssh keys, if they have access to the root keys, you've got bigger issues on hand. – UtahJarhead Oct 9 '12 at 1:53

If you just don't have root ssh access, but have sudo(8) rights on the machine, you can do it.

For example, by putting username ALL= NOPASSWD:/usr/bin/rsync in /etc/sudoers on remote host and doing:

rsync -a -e "ssh" --rsync-path="sudo rsync" localdir/

See this answer for details and more options of doing it.

Also, since users don't already exist on remote, you'll need to use --numeric-ids on your rsync line so they'll get preserved (but you'll only see their usernames and groups once you sync /etc/passwd and /etc/group, of course)

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