rsync over SSH

sshMany of us use SSH multiple times on a daily basis times to do simple, complicated, and often redundant tasks. Often times the tasks are those which could be scripted and automated. For instance, if you have to synchronize files with a server often throughout the day, a cron job would be the ideal way because then it will be done automatically and you don’t have to worry about it. If you use SSH keys without a password to access a server, you can expand on it by using rsync to synchronize those local and remote directories.

Here is the command you would use to make this happen:

rsync -e 'ssh -i ~/.ssh/id_rsa' -rulvhtpz /Users/user/file_to_sync

rsync options used

-r, recursive throughout directories
-u, skip files that are newer at the destination (meaning only update old files)
-l, copy symlinks as symlinks
-v, verbose; show all output as it happens
-h, display output in human readable format
-t, preserve times of files
-p, preserve permissions
-z, compress files during transfer to preserve bandwith

Making rsync convenient:

rsync is really nice when it comes to automation. Adding rsync to a crontab entry comes really handy. There are all kinds of options for cron – to view them, check out my knowledge base article on it.

If we want rsync to run automatically at 12pm and 4pm, this is what we would do:

Open up your terminal app and type the following:

crontab -e

Add the following lines to the file:

00 12 * * * rsync -e 'ssh -i ~/.ssh/id_rsa' -rulvhtpz /Users/user/file_to_sync
00 16 * * * rsync -e 'ssh -i ~/.ssh/id_rsa' -rulvhtpz /Users/user/file_to_sync

If you’re really clever

If you are a programmer and want your code to automatically synchronize to a remote server, add a macro to your IDE that somehow that adds the rsync code to a button in. For instance, if you add the rsync command to the save button command, maybe it will kill two birds with one stone.

For more information

Go into your terminal and type man rsync or rsync -h