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Tutorial and Examples to Copy, Mirror, Synchronize, Backup and Restore files

Rsync is a mechanism to mirror data on a single host or between multiple hosts.
Rsync can duplicate directories and files and provide backup/restore operations or mobile device synchronization. This tutorial covers Rsync client and server configurations for both Linux and MS/Windows (using Cygwin).

Tutorial Table of Contents:

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Rsync description, topologies and configuration:

Rsync can duplicate data between two directories whether the data is collocated on the same computer or over the network between two computers. The directories can be on any accessible random access storage devices (hard drives, thumb drives, etc). The data source must be readable and the destination must be writable.

The benefit of Rsync is the ability to update the mirrored backup with computed changes from the data source with a minimal load to system resources. It is very data bandwidth and system intensive to perform an entire copy of a directory structure each time a backup is to be performed. While the initial backup is no faster than a copy, Rsync has the ability to load the system in a minimal fashion by transferring only changes when subsequent rsync updates are performed.

Description of the rsync algorithm

Rsync single host: mirror between storage devices

Rsync single host mirror

Rsync client-server: mirror between two computers

Rsync client-server mirror

Rsync Single Host Operation:

Rsync command format: rsync [options] source-path destination-path

Synchronize directory paths each of which are accessible to a single system.

  • Back-up (push) your photo directories to a second drive:
    rsync -av ~/Pictures /mnt/drive2
    This creates a backup of your photos in /mnt/drive2/Pictures/
    Back-up to a USB thumb drive is similar: rsync -av ~/Pictures /media/KINGSTON
    When you add new photos, just re-execute this rsync command to backup the latest changes.
    Note: The drive name will be dependent on the manufacturer.

    [Potential Pitfall]: Do not include the source directory name in the destination.
    rsync -av ~/Pictures /mnt/drive2/Pictures
    This will result in /mnt/drive2/Pictures/Pictures/
    Note that rsync destinations acts just like the cp and rcp commands.
    Also note that rsync -av ~/Pictures/ /mnt/drive2/ has a different behavior from rsync -av ~/Pictures /mnt/drive2

  • Back-up (push) two directory source to a single directory on the second drive:
    rsync -av ~/Pictures ~/Images /mnt/drive2
    This creates a backup of your photos from the two directories in /mnt/drive2/Pictures/

  • Sync directories and if any were deleted in ~/Pictures, also delete it in /mnt/drive2/Pictures/:
    rsync -a --progress --delete ~/Pictures /mnt/drive2
    This creates a backup in /mnt/drive2/Pictures/

  • Sync one specific file in a directory:
    rsync -a ~/Pictures/Group-photo-2001-A.jpg /mnt/drive2/Pictures

  • Sync a group of specific files in a directory:
    rsync -a ~/Pictures/2001-*.jpg /mnt/drive2/Pictures
    This creates a backup in /mnt/drive2/Pictures/
    Note that when transferring files only, the directory name has to be provided in the destination path.

  • Sync files and directories listed in a file:
    rsync -ar --files-from=Filelist.txt ~/Data /mnt/drive2
    This creates a backup in /mnt/drive2/Data/
    Directory paths are included if specified with a closing slash such as pathx/pathy/pathz/. Path names must be terminated with a "/" or "/."

  • Back-up (push) your source code and compress to save space. Ignore object files:
    rsync -avz --delete --exclude='*.o' --exclude='*.so' ~/src /mnt/drive2
    This creates a backup in /mnt/drive2/src/ but does not transfer files with the ".o" and ".so" extensions.

  • Back-up (push) your source code and ignore object and shared object code files:
    rsync -av --delete --filter='+ *.[ch]' --filter='- *.o' ~/src /mnt/drive2
    This transfers files with the extension ".c" and ".h" but does not transfer object files with the ".o" extensions.
    same as rsync.exe -av --exclude='*.o' --filter='+ *.c *.h' ~/src /mnt/drive2

  • Back-up (push) your source code and ignore CM directories, object and shared object code files:
    rsync -artv --progress --delete --filter='+ *.[ch]' --filter='- *.o' --exclude=".svn" ~/src /mnt/drive2
    Note that --exclude overides the include filter --filter='+ *.[ch]' so that ".c" and ".h" files under .svn/ are not copied.
Referencing directories - errors and subtleties:
  • rsync -ar dir1 dir2
    This will copy dir1 into dir2 to give dir2/dir1 thus dir1/file.txt gets copied to dir2/dir1/file.txt
  • rsync -ar dir1/ dir2/
    This will copy the contents of dir1 into dir2 to give dir2/contents-of-dir1, eg dir1/file.txt gets copied to dir2/file.txt
    The following all achieve the same results:
    • rsync -ar dir1/ dir2/
    • rsync -ar dir1/* dir2
    • rsync -ar dir1/* dir2/
Rsync Options: (partial list)
Command line argumentDescription
Includes options:
  • -r: recursion
  • -l: preserve symbolic links as symbolic links. Opposite of -L
  • -p: preserve permissions (Linux/unix only)
  • -t: preserve file modification time
  • -g: preserve group ownership
  • -o: preserve user ownership
  • -D: preserve special files and devices (Linux/unix only)
Copy directory tree structure without copying the files within the directories
--existingUpdate only existing files from source directory which are already present at the destination. No new files will be transferred.
Transform a symbolic link to a copied file upon transfer
--statsPrint verbose set of statistics on the transfer
Add -h (--human-readable) to print stats in an understandable fashion
Preserve permissions (not relevant for MS/Windows client)
Recursive through directories and sub-directories
Preserve file modification times
Compress files during transfer to reduce network bandwidth. Files not stored in an altered or compressed state.
Note that compression will have little or no effect on JPG, PNG and files already using compression.
Use arguments --skip-compress=gz/bz2/jpg/jpeg/ogg/mp[34]/mov/avi/rpm/deb/ to avoid compressing files already compressed
--deleteDelete extraneous files from destination directories. Delete files on archive server if they were also deleted on client.
Use the argument -m (--prune-empty-dirs) to delete empty directories (no longer useful after its contents are deleted)
Specify a pattern for specific inclusion or exclusion or use the more universal filter for inclusion (+)/exclusion (-).
Do not transfer files ending with ".o": --exclude='*.o'
Transfer all files ending with ".c" or ".h": --filter='+ *.[ch]'
Print information about the transfer. List everything (all file copies and file changes) rsync is going to perform
Don't copy anything, just list what rsync would copy if this option was not given. This helps when debugging the correct exclusion/inclusion filters.
--progressShows percent complete, Kb transferred and Kb/s transfer rate. Includes verbose output.
For all options see the rsync man page

Note that rsync will be able to handle files with blanks in the file name or directory name as well as with dashes ("-") or underscores ("_").

Rsync Client-Server Configuration and Operation:

Rsync can be configured in multiple client-server modes.
  1. connect client to a sever running rsync in daemon mode
  2. connect client to a sever using a ssh shell
These configurations are specified with the use of the colon ":"
  • Double colon refers to a connection to a host running the rsync daemon in the format hostname::module/path where the module name is identified by the configuration in /etc/rsyncd.conf. The double colon is equivalent to using the URL prefix rsync://
  • Single colon refers to the use of a remote shell
  • No colon then the directory is considered to be local to the system.

1) Rsync daemon server:

The Rsync server is often referred to as rsyncd or the rsync daemon. This is in fact the same rsync executable run with the command line argument "--daemon". This can be run stand-alone or using xinetd as is typically configured on most Linux distributions.

Configure xinetd to manage rsync:

File: /etc/xinetd.d/rsync

Default: "disable = yes". Change to "disable = no"

service rsync
        disable = no
        flags           = IPv6
        socket_type     = stream
        wait            = no
        user            = root
        server          = /usr/bin/rsync
        server_args     = --daemon
        log_on_failure  += USERID
Start/Re-start xinetd: /etc/rc.d/init.d/xinetd restart
For more information on xinetd see the YoLinux xinetd tutorial.

Typical Linux distributions do not pre-configure rsync for server use. Both Ubuntu and Red Hat based distributions require that one generates the configuration file "/etc/rsyncd.conf"

File: /etc/rsyncd.conf

log file = /var/log/rsyncd.log
hosts allow =,
hosts deny = *
list = true
uid = root
gid = root
read only = false

path = /tmp/Proj1
comment = Project 1 rsync directory

path = /var/ProjX
comment = Project X rsync directory
rsyncd.conf man page

Client command to rsync to the server:

Push: rsync -avr /home/user1/Proj1/Data server-host-name::Proj1
(eg. update server backup from mobile laptop)
This will initially copy over directory Data and all of its contents to /tmp/Proj1/Data on the remote server.

Pull: rsync -avr server-host-name::Proj1 /home/user1/Proj1/Data
(eg. update mobile laptop from server backup)

2) Rsync to server using ssh shell:
Using this method does not use the configuration "modules" in /etc/rsyncd.conf but instead uses the paths as if logged in using ssh.

First configure ssh for "password-less" login:
Note that current Linux distributions use ssh version 2 and rsa.

[user1@myclient ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/user1/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/user1/.ssh/id_rsa.
Your public key has been saved in /home/user1/.ssh/id_rsa.pub.
The key fingerprint is:
Note that "Enter" was pressed when asked for a "passphrase" to take the default.
Two files are generated:
  • Local client (private key): ~/.ssh/id_rsa
  • Contents (one line) of file (public key): ~/.ssh/id_rsa.pub to be copied into file on server: ~/.ssh/authorized_keys
Note file protection on file:
[user1@myclient ~]$ ls -l ~/.ssh/id_rsa
-rw-------. 1 user1 user1 1675 Sep  7 14:55 /home/user1/.ssh/id_rsa
Copy public key to server so you can login.
Use the following command:
[user1@myclient ~]$ ssh-copy-id -i ~/.ssh/id_rsa.pub user1@remote-server
user1@remote-server's password: 
Now try logging into the machine, with "ssh 'user1@remote-server'", and check in: .ssh/authorized_keys to make sure we haven't added extra keys that you weren't expecting.

Test "password-less" ssh connection: ssh remote-server
This command should log you in without asking for a password.

Now try rsync (push) using ssh:
rsync -avr --rsh=/usr/bin/ssh /home/user1/Proj1/Data remote-server:/mnt/supersan/Proj1

Note that if this connection is is to be spawned by a cron job (eg. root user) then the shell user ID must be provided: user1@
rsync -avr --rsh=/usr/bin/ssh /home/user1/Proj1/Data user1@remote-server:/mnt/supersan/Proj1

SSH options may be put in the file ~/.ssh/config

  • Sync local directory with a remote directory (push):
    rsync -avr --rsh=/usr/bin/ssh /home/user1/Proj1/data/ user1@remote-server:/mnt/supersan/Proj1/data/
    This will alter the remote directory to match the local.
    Note that this is not the same as:
    rsync -avr --rsh=/usr/bin/ssh /home/user1/Proj1/data user1@remote-server:/mnt/supersan/Proj1/data
    which will result in a remote directory: /mnt/supersan/Proj1/data/data/
  • Sync local directory with a remote directory (pull):
    rsync -avr --rsh=/usr/bin/ssh user1@remote-server:/home/user1/Proj1/data/ /mnt/supersan/Proj1/data/
    This will alter the local directory to match the remote.

For more examples with the discussions of the nuances of rsync, see the examples above for the "Single Host Operation".

Rsync to Amazon AWS/EC2:

Amazon cloud authentication is via a key-file. Reference this key-file (pem file) to rsync to the server "instance1" in the cloud:
rsync -artv --delete -e "ssh -i /home/user1/.ssh/instance1.pem" /home/user1/dir1/dir2/          ec2-user@ec2-xxx-xxx-xxx-xxx.us-yyyy-1.compute.amazonaws.com:/home/ec2-user/dir1/dir2/


Note that rsync is often used with cron to perform a nightly rsync.

eg. Rsync to get latest updates to the web server at 2:00am:

File: /etc/crontab
* 2 * * * rsync -avr server-host-name::Proj1/html /var/www > /var/log/rsync 2>&1
See the crontab man page

MS/Windows Rsync Client and Server Operation:

Multiple solutions exist for MS/Windows rsync clients but they all rely on Cygwin. There is no other port of rsync.

  • Cygwin: Work in Cygwin shell environment
  • DeltaCopy (client and server)
    Uses Rsync algorithm and protocol
  • QtdSync: (client and server) MS/Windows version includes Cygwin rsync and ssh (and more)

Cygwin rsync client for MS/Windows:

Cygwin must be installed for the purpose of this tutorial.
Be sure to install the Cygwin component "Net" + "rsync".

Rsync Cygwin components:
These components can be extracted for a minimal installation of be left in place as part of the complete Cygwin package.

DOS bat script to perform an rsync (push):
@set PATH=C:\cygwin\bin
@set LIB=C:\cygwin\bin
rsync.exe -avr /cygdrive/c/MISC/JUNK  remote-server::Proj1

[Potential Pitfall]: The following command: rsync.exe -avr c:MISC\JUNK remote-server::Proj1 will produce an error because rsync will interpret the "C:" as the remote host and not a drive letter. Drive letters are not POSIX compliant.

[Potential Pitfall]: The following commands:

cd c:\
rsync.exe -avr MISC\JUNK  remote-server::Proj1
will generate a single directory of the name 'MISC\JUNK' (not two directories, one within the other but just one with that name). The "/" will not be a directory delimiter but a character in the directory name (bad).

For more on Cygwin POSIX paths: http://cygwin.com/cygwin-ug-net/using.html#using-pathnames

MS/Windows rsync client GUI:

I chose QtdSync/cygwin as it provided a GUI and an isolated Cygwin rsync executable and its dependencies.

QtdSync GUI:
Rsync QdtSync MS/Windows client GUI

To list GUI command line arguments: C:\Program Files\QtdSync\QtdSync.exe --help

Includes rsync Cygwin components:

  C:\Program Files\QtdSync\bin\rsync.exe 
Where the file C:\Program Files\QtdSync\etc\fstab has the following contents:
none /cygdrive cygdrive binary,posix=0,user,noacl 0 0
Note: QtdSync does not require the separate installation of cygwin.

DOS bat script to perform an rsync (push):
@set PATH=C:\Program Files\QtdSync\bin
@set LIB=C:\Program Files\QtdSync\bin
rsync.exe -avr /cygdrive/c/MISC/JUNK  remote-server::Proj1

A Cygwin MS/Windows rsyncd server configuration:

Rsync daemon configuration requires installing rsync as a MS/Windows service. Use the Cygwin command cygrunsrv command (installed under the Cygwin "Admin" category).

cygrunsrv command options:
Install as a service
Remove as a service
Start the service
Stop the service
Arguments to pass the daemon service
-hCommand help instructions

Install rsync as a MS/Windows service: regrsyncd.bat
@set PATH=C:\cygwin\bin
@set LIB=C:\cygwin\bin
cygrunsrv -I rsyncd -e CYGWIN=nontsec --path /cygdrive/c/cygwin/bin/rsync.exe \ 
          -a "--daemon --config=/etc/rsyncd.conf --no-detach"
You may be required to include the system user login and password:
cygrunsrv -I rsyncd -e CYGWIN=nontsec --path /cygdrive/c/cygwin/bin/rsync.exe \
          -a "--daemon --config=/etc/rsyncd.conf --no-detach" -u Administrator -w super-secret-password

Note that Cygwin applications refer to configuration file referenced within the Cygwin environment. As viewed by the Cygwin rsync application, the file /etc/rsyncd.conf is actually C:\cygwin\etc\rsyncd.conf as viewed by the MS/Windows OS.

Where the option -e CYGWIN=nontsec turns off Microsoft Windows NT security permissions. On MS/Windows 7 use the following c:\cygwin\etc\fstab settings:

none /cygdrive cygdrive binary,posix=0,user,noacl 0 0
fstab man page

This is to avoid the following error:
rsync: failed to modify permissions on xxxxfilenamexxxx: Permission denied

File: C:\cygwin\etc\rsyncd.conf

log file = /var/log/rsyncd
hosts allow =,
hosts deny = *
list = true
use chroot = false
strict modes = false
read only = false
ignore nonreadable = yes
dont compress = *.gz *.tgz *.zip *.rpm *.deb *.iso *.bz2 *.jpg *.mpg *.mpeg

path = /cygdrive/c/Proj1
comment = Project 1 rsync directory
rsyncd.conf man page

Where the Cygwin log file /var/log/rsyncd is C:\cygwin\var\log\rsyncd as viewed by the MS/Windows OS.

The Cygwin rsync directory path /cygdrive/c/Proj1 is C:\Proj1\ as viewed by the MS/Windows OS.

Check to see if the rsyncd service is running: Control Panel --> Administrative Tools --> Services

Microsoft Windows rsyncd service

Find "rsync". If not running, select the service and select "start" or issue the command "net start rsync".

[Potential Pitfall]: You must check to see if the service has started. If not select "Start the service". The Microsoft Windows firewall may not allow a system to attach to rsyncd on port 873. My experience is that the service is detected by the OS and added to the firewall privileges. I did not have to configure the firewall, registration was automatic. If the rsyncd service did not get registered with the MS/Windows firewall, one may have to specifically grant the permission to to the rsyncd service.

Select "Control panel" + Windows Firewall":

Microsoft Windows firewall settings

Microsoft Windows firewall settings

Microsoft Windows firewall settings

Microsoft Windows firewall settings

To remove rsyncd from the available list of services, execute the following command from a "cmd" terminal:
c:\cygwin\bin\cygrunsrv -R rsyncd

Debugging Rsync:

Using telnet to test an rsync connection:

One can use telnet to test connectivity with an Rsync server:

[bash]$ telnet  873
Connected to
Escape character is '^]'.
@RSYNCD: 30.0
Connection closed by foreign host.
This is the proper response when using telnet to connect to rsync.

This is representative of a telnet connection to a misconfigured rsync server or one which has not yet been started (nothing for the client to connect to):

[bash]$ telnet  873
 telnet: connect to address Connection timed out

does not get past this and times out.

Rsync client responses:

An rsync server which has been shut down or was never started will cause the rsync client to behave as follows:
[bash]$ rsync -avr /home/user1/Test
rsync: failed to connect to Connection timed out (110)
rsync error: error in socket IO (code 10) at clientserver.c(124) [receiver=3.0.6]

Rsync logs:

Check the rsyncd log file: /var/log/rsyncd.log
2011/09/08 21:13:10 [1032] rsyncd version 2.6.6 starting, listening on port 873
2011/09/08 21:17:10 [3156] rsync error: received SIGUSR1 or SIGINT (code 20)
compared to normal logging of a client connection and file transfer:
2011/09/08 21:19:10 [2796] rsync on Proj1/ from
2011/09/08 21:19:10 [2796] sent 940 bytes  received 334 bytes  total size 97


Public rsync servers:


"Backup & Recovery: Inexpensive Backup Solutions for Open Systems"
by W. Curtis Preston
ISBN # 0596102461, O'Reily Media (Jan 2007)

Covers backup utilities including tar, dump, cpio, ntbackup, ditto, rsync, AMANDA, Bacula, BackupPC, rdiff-backup, and rsnapshot.


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