Tuesday, August 24, 2010

How to use rsync for transferring files under Linux or UNIX


How do you install and use rsync to synchronize files and directories from one location (or one server) to another location? - A common question asked by new sys admin.

rsync is a free software computer program for Unix and Linux like systems which synchronizes files and directories from one location to another while minimizing data transfer using delta encoding when appropriate. An important feature of rsync not found in most similar programs/protocols is that the mirroring takes place with only one transmission in each direction.

So what is unique about rsync?

It can perform differential uploads and downloads (synchronization) of files across the network, transferring only data that has changed. The rsync remote-update protocol allows rsync to transfer just the differences between two sets of files across the network connection.

How do I install rsync?

Use any one of the following commands to install rsync.

If you are using Debian or Ubuntu Linux, type the following command

# apt-get install rsync
$ sudo apt-get install rsync

If you are using Red Hat Enterprise Linux (RHEL), type the following command

# up2date rsync

If you are using CentOS/Fedora Core Linux, type the following command

# yum install rsync

Always use rsync over ssh

Since rsync does not provide any security while transferring data it is recommended that you use rsync over ssh . This allows a secure remote connection. Now let us see some examples of rsync.

rsync command common options

  • --delete : delete files that don't exist on sender (system)
  • -v : Verbose (try -vv for more detailed information)
  • -e "ssh options" : specify the ssh as remote shell
  • -a : archive mode
  • -r : recurse into directories
  • -z : compress file data

Task : Copy file from a local computer to a remote server

Copy file from /www/backup.tar.gz to a remote server called openbsd.nixcraft.in
$ rsync -v -e ssh /www/backup.tar.gz jerry@openbsd.nixcraft.in:~Output:

sent 19099 bytes received 36 bytes 1093.43 bytes/sec
total size is 19014 speedup is 0.99

Please note that symbol ~ indicate the users home directory (/home/jerry).

Task : Copy file from a remote server to a local computer

Copy file /home/jerry/webroot.txt from a remote server openbsd.nixcraft.in to a local computer /tmp directory:
$ rsync -v -e ssh jerry@openbsd.nixcraft.in:~/webroot.txt /tmp

Task: Synchronize a local directory with a remote directory

$ rsync -r -a -v -e "ssh -l jerry" --delete openbsd.nixcraft.in:/webroot/ /local/webroot

Task: Synchronize a remote directory with a local directory

$ rsync -r -a -v -e "ssh -l jerry" --delete /local/webroot openbsd.nixcraft.in:/webroot

Task: Synchronize a local directory with a remote rsync server

$ rsync -r -a -v --delete rsync://rsync.nixcraft.in/cvs /home/cvs

Task: Mirror a directory between my "old" and "new" web server/ftp

You can mirror a directory between my "old" (my.old.server.com) and "new" web server with the command (assuming that ssh keys are set for password less authentication)
$ rsync -zavrR --delete --links --rsh="ssh -l vivek" my.old.server.com:/home/lighttpd /home/lighttpd

Read related previous articles

Other options - rdiff and rdiff-backup

There also exists a utility called rdiff, which uses the rsync algorithm to generate delta files Using rdiff. A utility called rdiff-backup has been created which is capable of maintaining a backup mirror of a file or directory over the network, on another server. rdiff-backup stores incremental rdiff deltas with the backup, with which it is possible to recreate any backup point. Next time I will write about these Utilities :)

rsync for Windows server/XP

Please note if you are using Windows, try any one of the program:

  1. DeltaCopy
  2. NasBackup

No comments: