rsync copying tool
What is rsync?
Rsync is a fast and powerful file copying tool. Rsync can copy locally, to and from another host over any remote shell, or to and from a remote rsync daemon. Rsync has a vast set of options that allow you to control virtually every aspect of its behaviour and the way files are copied. Rsync is known for its "delta-transfer" algorithm which reduces the amount of data transferred over a network by sending only the differences between the source files and the existing files in the destination. This makes rsync extremely useful as a backup tool.
The rsync tool locates files that need to be transferred using a "quick check" algorithm that looks for any files that have changed in size or changes in the last-modified time.
Rsync is generally run from a command line or from within a script which makes it ideally suited for making backups. Many tools are also available with a GUI (Graphical User Interface) that allow you to configure backups quickly. An example of a GUI rsync tool is "Grsync". Grsync is basically a front end to the "rsync" command and is available within most repositories.
Below are examples of some basic uses of the "rsync" command for copying files:
Retrieving files from a remote host with rsync
The following rsync command retrieves files from a remote location to a specified directory. In the following example we are going to use our local machine "Mint" and our remote machine "CentOS":
"Mint" currently has no files in the directory below:
$ pwd /home/tux/rsync_test $ ls -l total 0
"CentOS" has the following files in its directory:
$ pwd /home/tux/data $ ls -l total 20 -rw-rw-r--. 1 tux tux 110 May 23 18:46 file1.img -rw-rw-r--. 1 tux tux 158 May 23 18:46 file2.img -rw-rw-r--. 1 tux tux 206 May 23 18:46 file3.img -rw-rw-r--. 1 tux tux 254 May 23 18:46 file4.img -rw-rw-r--. 1 tux tux 302 May 23 18:46 file5.img
On our local machine "Mint" we are going to issue the command:
rsync -v -e ssh firstname.lastname@example.org:/home/tux/data/* .
This command will copy the files from the remote "CentOS" machine to our local directory. The "dot" "." after the remote directory location specifies to copy to the current directory on the local machine:
tux@mint01a:~/rsync_test$ pwd /home/tux/rsync_test tux@mint01a:~/rsync_test$ rsync -v -e ssh email@example.com:/home/tux/data/* . firstname.lastname@example.org's password: file1.img file2.img file3.img file4.img file5.img sent 119 bytes received 1,357 bytes 328.00 bytes/sec total size is 1,030 speedup is 0.70
First we will be asked to supply a password for the remote machine. Once authenticated, our files should be copied to our local machine in our current directory. If we now issue the "ls -l" command on our local machine we should see that the files have been transferred successfully.
tux@mint01a:~/rsync_test$ pwd /home/tux/rsync_test tux@mint01a:~/rsync_test$ ls -l total 20 -rw-rw-r-- 1 tux tux 110 May 23 19:46 file1.img -rw-rw-r-- 1 tux tux 158 May 23 19:46 file2.img -rw-rw-r-- 1 tux tux 206 May 23 19:46 file3.img -rw-rw-r-- 1 tux tux 254 May 23 19:46 file4.img -rw-rw-r-- 1 tux tux 302 May 23 19:46 file5.img
Notice, the files that have been copied have a different time stamp to the original files on the remote "CentOS" machine. If we wanted to preserve this time stamp, then we can modify our command to include the "-t" option to preserve our time stamp information:
rsync -vt -e ssh email@example.com:/home/tux/data/* .
tux@mint01a:~/rsync_test$ rsync -vt -e ssh firstname.lastname@example.org:/home/tux/data/* . email@example.com's password: file1.img file2.img file3.img file4.img file5.img sent 149 bytes received 327 bytes 136.00 bytes/sec total size is 1,030 speedup is 2.16 tux@mint01a:~/rsync_test$ ls -l total 20 -rw-rw-r-- 1 tux tux 110 May 23 18:46 file1.img -rw-rw-r-- 1 tux tux 158 May 23 18:46 file2.img -rw-rw-r-- 1 tux tux 206 May 23 18:46 file3.img -rw-rw-r-- 1 tux tux 254 May 23 18:46 file4.img -rw-rw-r-- 1 tux tux 302 May 23 18:46 file5.img
This time the "time stamp" information has been preserved and should match that of the original files from the remote "CentOS" machine.
Copying a local file to a remote server with rsync
In the next example we are going to copy a local file to our remote "CentOS" machine.
For this example, we have added a new file called mint_file.txt into our current directory:
tux@mint01a:~/rsync_test$ ls -l total 24 -rw-rw-r-- 1 tux tux 110 May 23 18:46 file1.img -rw-rw-r-- 1 tux tux 158 May 23 18:46 file2.img -rw-rw-r-- 1 tux tux 206 May 23 18:46 file3.img -rw-rw-r-- 1 tux tux 254 May 23 18:46 file4.img -rw-rw-r-- 1 tux tux 302 May 23 18:46 file5.img -rw-rw-r-- 1 tux tux 2608 May 23 19:55 mint_file.txt
Now on our local machine (Mint) we issue the following command:
rsync -avz /home/tux/rsync_test/ firstname.lastname@example.org:/home/tux/data/
tux@mint01a:~/rsync_test$ rsync -avz /home/tux/rsync_test/ email@example.com:/home/tux/data/ firstname.lastname@example.org's password: sending incremental file list ./ mint_file.txt sent 1,526 bytes received 38 bytes 347.56 bytes/sec total size is 3,638 speedup is 2.33
Now if we take a look at the remote "CentOS" machine:
[tux@centos8a data]$ pwd /home/tux/data [tux@centos8a data]$ ls -l total 24 -rw-rw-r--. 1 tux tux 110 May 23 18:46 file1.img -rw-rw-r--. 1 tux tux 158 May 23 18:46 file2.img -rw-rw-r--. 1 tux tux 206 May 23 18:46 file3.img -rw-rw-r--. 1 tux tux 254 May 23 18:46 file4.img -rw-rw-r--. 1 tux tux 302 May 23 18:46 file5.img -rw-rw-r--. 1 tux tux 2608 May 23 19:55 mint_file.txt
We can see that the new file has been transferred.
rsync with ssh
In all of the previous examples so far we have had to supply our credentials (password) each time we connect to the remote "CentOS" machine. It is possible to create what is known as a public key which can then be copied to the remote server. This will then allow us to login without supplying a password. To achieve this we must carry out the following actions.
Creating a Public key
As with SSH, the "rsync" command can use "Public Key Authentication" to connect to a server without needing to enter a password. This functionality is useful if you need to transfer files from a script as you will not need to enter a password to authenticate.
Below is the process required for generating a public key
Generating a public key
Using an utility called "ssh-keygen", you can create a public key that can be distributed to servers that you require access to.
The following key has been generated on a Linux Mint system.
tux@mint01a:~$ ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/tux/.ssh/id_rsa): Created directory '/home/tux/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/tux/.ssh/id_rsa Your public key has been saved in /home/tux/.ssh/id_rsa.pub The key fingerprint is: SHA256:QdfQJfNmO2eixOQOrjKYKcmsVNbPdpJ+C8VGev10BhI tux@mint01a The key's randomart image is: +---[RSA 3072]----+ | . oEo.. | | . . ++ | | .. ...+ | | . +..+.o.. | | o . .S=..+.+oo| | o o =. +o.o= | | + . + B .. o. | |. = + = +o | |.. . +o.. | +----[SHA256]-----+
In the above example we chose to use the "rsa" (Rivest, Shamir, Adleman) algorithm to create our digital signature. We could have chosen "dsa". Next we were prompted to supply a directory where we would like the key to be saved. In the example I pressed "Enter" to accept the default location of "/home/tux/.ssh/id_rsa". Next, We were asked to enter a passphrase. I chose not to enter a passphrase. All that is required now is to distribute our public key to our desired remote server.
tux@mint01a:~$ cd /home/tux/.ssh tux@mint01a:~/.ssh$ ls -l total 8 -rw------- 1 tux tux 2602 May 23 11:32 id_rsa -rw-r--r-- 1 tux tux 565 May 23 11:32 id_rsa.pub
Copying Public keys to remote servers
In the above example of the "ssh-keygen -t rsa" command we can see that a public key was created.
My public key has been saved in /home/tux/.ssh/id_rsa.pub
To use the public key, we have to first copy the contents of the file "id_rsa.pub" to a file called "authorized_keys" on the remote server. Whenever copying a new key to a remote servers authorized_keys file, always use the append option. If you copy your files content, you could overwrite the file and destroy any other keys that may be located there. The easiest way to transfer the key to the remote server is to issue a command similar to the one below.
Note, the "authorized_keys" key file must already exist on the remote server under the account you are logging into.
In the example below, I will create the directory structure and authorized_keys file on the remote server as follows:
[tux@centos8a ~]$ pwd /home/tux [tux@centos8a ~]$ ls -al total 12 drwx------. 2 tux tux 62 May 23 11:31 . drwxr-xr-x. 4 root root 29 May 23 11:31 .. -rw-r--r--. 1 tux tux 18 Jul 21 2020 .bash_logout -rw-r--r--. 1 tux tux 141 Jul 21 2020 .bash_profile -rw-r--r--. 1 tux tux 376 Jul 21 2020 .bashrc [tux@centos8a ~]$ mkdir .ssh [tux@centos8a ~]$ chmod 700 .ssh/ [tux@centos8a ~]$ cd .ssh [tux@centos8a .ssh]$ touch authorized_keys [tux@centos8a .ssh]$ chmod 600 authorized_keys [tux@centos8a .ssh]$ ls -l total 0 -rw-------. 1 tux tux 0 May 23 11:46 authorized_keys
Note, I had to create the ".ssh directory first, set its permissions to "700" and then create the empty "authorized_keys" file using the "touch" command. The permissions on the "authorized_keys" file are also set to "600".
Once the above is in place, I can copy the contents of our public key to this file.
$ cat $HOME/.ssh/id_rsa.pub | ssh 192.168.122.75 'cat >> .ssh/authorized_keys && echo "Contents Copied Successfully"' email@example.com's password: Contents Copied Successfully
The above command simply appends the key on our local server to the "authorized_keys" file on the remote server. (Amend IP address to match your remote server)
Testing rsync Access with Public Key
Once the public key has successfully been copied to the correct location on the remote server, you should now be able to login to the remote server without specifying a password.
On our local machine "Mint", I have created a new file called "landoflinux.com.txt".
tux@mint01a:~/rsync_test$ pwd /home/tux/rsync_test tux@mint01a:~/rsync_test$ ls -rtl total 28 -rw-rw-r-- 1 tux tux 110 May 23 18:46 file1.img -rw-rw-r-- 1 tux tux 158 May 23 18:46 file2.img -rw-rw-r-- 1 tux tux 254 May 23 18:46 file4.img -rw-rw-r-- 1 tux tux 206 May 23 18:46 file3.img -rw-rw-r-- 1 tux tux 302 May 23 18:46 file5.img -rw-rw-r-- 1 tux tux 2608 May 23 19:55 mint_file.txt -rw-rw-r-- 1 tux tux 2498 May 23 20:04 landoflinux.com.txt
Now lets issue the "rsync" command: rsync -avz /home/tux/rsync_test/ firstname.lastname@example.org:/home/tux/data/
tux@mint01a:~/rsync_test$ rsync -avz /home/tux/rsync_test/ email@example.com:/home/tux/data/ sending incremental file list ./ landoflinux.com.txt sent 1,078 bytes received 38 bytes 744.00 bytes/sec total size is 6,136 speedup is 5.50
This time we didn't get asked for a password! The only file that was transferred was the "landoflinux.com.txt" file. We can confirm this by looking at the remote "CentOS" server:
[tux@centos8a data]$ pwd /home/tux/data [tux@centos8a data]$ ls -l total 28 -rw-rw-r--. 1 tux tux 110 May 23 18:46 file1.img -rw-rw-r--. 1 tux tux 158 May 23 18:46 file2.img -rw-rw-r--. 1 tux tux 206 May 23 18:46 file3.img -rw-rw-r--. 1 tux tux 254 May 23 18:46 file4.img -rw-rw-r--. 1 tux tux 302 May 23 18:46 file5.img -rw-rw-r--. 1 tux tux 2498 May 23 20:04 landoflinux.com.txt -rw-rw-r--. 1 tux tux 2608 May 23 19:55 mint_file.txt
To get a full overview of the "rsync" command, I would recommend reading the "man pages" for rsync. An overview of some of the options that can be used with the rsync command follow. To view this option you can issue the command "rsync --help" or "man rsync".
Usage: rsync [OPTION]... SRC [SRC]... DEST or rsync [OPTION]... SRC [SRC]... [USER@]HOST:DEST or rsync [OPTION]... SRC [SRC]... [USER@]HOST::DEST or rsync [OPTION]... SRC [SRC]... rsync://[USER@]HOST[:PORT]/DEST or rsync [OPTION]... [USER@]HOST:SRC [DEST] or rsync [OPTION]... [USER@]HOST::SRC [DEST] or rsync [OPTION]... rsync://[USER@]HOST[:PORT]/SRC [DEST] The ':' usages connect via remote shell, while '::' & 'rsync://' usages connect to an rsync daemon, and require SRC or DEST to start with a module name. Options -v, --verbose increase verbosity --info=FLAGS fine-grained informational verbosity --debug=FLAGS fine-grained debug verbosity --msgs2stderr special output handling for debugging -q, --quiet suppress non-error messages --no-motd suppress daemon-mode MOTD (see manpage caveat) -c, --checksum skip based on checksum, not mod-time & size -a, --archive archive mode; equals -rlptgoD (no -H,-A,-X) --no-OPTION turn off an implied OPTION (e.g. --no-D) -r, --recursive recurse into directories -R, --relative use relative path names --no-implied-dirs don't send implied dirs with --relative -b, --backup make backups (see --suffix & --backup-dir) --backup-dir=DIR make backups into hierarchy based in DIR --suffix=SUFFIX set backup suffix (default ~ w/o --backup-dir) -u, --update skip files that are newer on the receiver --inplace update destination files in-place (SEE MAN PAGE) --append append data onto shorter files --append-verify like --append, but with old data in file checksum -d, --dirs transfer directories without recursing -l, --links copy symlinks as symlinks -L, --copy-links transform symlink into referent file/dir --copy-unsafe-links only "unsafe" symlinks are transformed --safe-links ignore symlinks that point outside the source tree --munge-links munge symlinks to make them safer (but unusable) -k, --copy-dirlinks transform symlink to a dir into referent dir -K, --keep-dirlinks treat symlinked dir on receiver as dir -H, --hard-links preserve hard links -p, --perms preserve permissions -E, --executability preserve the file's executability --chmod=CHMOD affect file and/or directory permissions -A, --acls preserve ACLs (implies --perms) -X, --xattrs preserve extended attributes -o, --owner preserve owner (super-user only) -g, --group preserve group --devices preserve device files (super-user only) --copy-devices copy device contents as regular file --specials preserve special files -D same as --devices --specials -t, --times preserve modification times -O, --omit-dir-times omit directories from --times -J, --omit-link-times omit symlinks from --times --super receiver attempts super-user activities --fake-super store/recover privileged attrs using xattrs -S, --sparse turn sequences of nulls into sparse blocks --preallocate allocate dest files before writing them -n, --dry-run perform a trial run with no changes made -W, --whole-file copy files whole (without delta-xfer algorithm) --checksum-choice=STR choose the checksum algorithms -x, --one-file-system don't cross filesystem boundaries -B, --block-size=SIZE force a fixed checksum block-size -e, --rsh=COMMAND specify the remote shell to use --rsync-path=PROGRAM specify the rsync to run on the remote machine --existing skip creating new files on receiver --ignore-existing skip updating files that already exist on receiver --remove-source-files sender removes synchronized files (non-dirs) --del an alias for --delete-during --delete delete extraneous files from destination dirs --delete-before receiver deletes before transfer, not during --delete-during receiver deletes during the transfer --delete-delay find deletions during, delete after --delete-after receiver deletes after transfer, not during --delete-excluded also delete excluded files from destination dirs --ignore-missing-args ignore missing source args without error --delete-missing-args delete missing source args from destination --ignore-errors delete even if there are I/O errors --force force deletion of directories even if not empty --max-delete=NUM don't delete more than NUM files --max-size=SIZE don't transfer any file larger than SIZE --min-size=SIZE don't transfer any file smaller than SIZE --partial keep partially transferred files --partial-dir=DIR put a partially transferred file into DIR --delay-updates put all updated files into place at transfer's end -m, --prune-empty-dirs prune empty directory chains from the file-list --numeric-ids don't map uid/gid values by user/group name --usermap=STRING custom username mapping --groupmap=STRING custom groupname mapping --chown=USER:GROUP simple username/groupname mapping --timeout=SECONDS set I/O timeout in seconds --contimeout=SECONDS set daemon connection timeout in seconds -I, --ignore-times don't skip files that match in size and mod-time -M, --remote-option=OPTION send OPTION to the remote side only --size-only skip files that match in size -@, --modify-window=NUM set the accuracy for mod-time comparisons -T, --temp-dir=DIR create temporary files in directory DIR -y, --fuzzy find similar file for basis if no dest file --compare-dest=DIR also compare destination files relative to DIR --copy-dest=DIR ... and include copies of unchanged files --link-dest=DIR hardlink to files in DIR when unchanged -z, --compress compress file data during the transfer --compress-level=NUM explicitly set compression level --skip-compress=LIST skip compressing files with a suffix in LIST -C, --cvs-exclude auto-ignore files the same way CVS does -f, --filter=RULE add a file-filtering RULE -F same as --filter='dir-merge /.rsync-filter' repeated: --filter='- .rsync-filter' --exclude=PATTERN exclude files matching PATTERN --exclude-from=FILE read exclude patterns from FILE --include=PATTERN don't exclude files matching PATTERN --include-from=FILE read include patterns from FILE --files-from=FILE read list of source-file names from FILE -0, --from0 all *-from/filter files are delimited by 0s -s, --protect-args no space-splitting; only wildcard special-chars --address=ADDRESS bind address for outgoing socket to daemon --port=PORT specify double-colon alternate port number --sockopts=OPTIONS specify custom TCP options --blocking-io use blocking I/O for the remote shell --stats give some file-transfer stats -8, --8-bit-output leave high-bit chars unescaped in output -h, --human-readable output numbers in a human-readable format --progress show progress during transfer -P same as --partial --progress -i, --itemize-changes output a change-summary for all updates --out-format=FORMAT output updates using the specified FORMAT --log-file=FILE log what we're doing to the specified FILE --log-file-format=FMT log updates using the specified FMT --password-file=FILE read daemon-access password from FILE --list-only list the files instead of copying them --bwlimit=RATE limit socket I/O bandwidth --stop-at=y-m-dTh:m Stop rsync at year-month-dayThour:minute --time-limit=MINS Stop rsync after MINS minutes have elapsed --outbuf=N|L|B set output buffering to None, Line, or Block --write-batch=FILE write a batched update to FILE --only-write-batch=FILE like --write-batch but w/o updating destination --read-batch=FILE read a batched update from FILE --protocol=NUM force an older protocol version to be used --iconv=CONVERT_SPEC request charset conversion of filenames --checksum-seed=NUM set block/file checksum seed (advanced) --noatime do not alter atime when opening source files -4, --ipv4 prefer IPv4 -6, --ipv6 prefer IPv6 --version print version number (-h) --help show this help (-h is --help only if used alone)