Red Hat System Administration II
Efficiently and securely synchronize the contents of a local file or directory with a remote server copy.
The rsync command is another way to copy files from one system to another system securely.
The tool uses an algorithm that minimizes copied data by synchronizing only the changed portions of files.
If two files or directories are similar between two servers, then the rsync command copies only the differences between the file systems.
An advantage of the rsync command is that it copies files securely and efficiently between a local system and a remote system.
Whereas an initial directory synchronization takes about the same time as copying it, subsequent synchronizations copy only the differences over the network, which substantially accelerates updates.
Use the rsync command -n option for a dry run.
A dry run simulates what happens when the command is executed.
The dry run shows the changes that the rsync command would perform when executing the command.
Perform a dry run before the actual rsync command operation to ensure that no critical files are overwritten or deleted.
When synchronizing with the rsync command, two standard options are the -v and -a options.
The rsync command -v or --verbose option provides a more detailed output.
This option is helpful for troubleshooting and viewing live progress.
The rsync command -a or --archive option enables "archive mode".
This option enables recursive copying and turns on many valuable options to preserve most characteristics of the files.
Archive mode is the same as specifying the following options:
Table 4.1. Options Enabled with rsync -a (Archive Mode)
| Option | Description |
|---|---|
-r, --recursive
| Synchronize the whole directory tree recursively |
-l, --links
| Synchronize symbolic links |
-p, --perms
| Preserve permissions |
-t, --times
| Preserve time stamps |
-g, --group
| Preserve group ownership |
-o, --owner
| Preserve the owner of the files |
-D, --devices
| Preserve device files |
Archive mode does not preserve hard links, because it might add significant time to the synchronization.
Use the rsync command -H option to preserve hard links too.
Note
To include extended attributes when syncing files, add these options to the rsync command:
-Ato preserve Access Control Lists (ACLs)-Xto preserve SELinux file contexts
You can use the rsync command to synchronize the contents of a local file or directory with a file or directory on a remote machine, with either machine as the source.
You can also synchronize the contents of two local files or directories on the same machine.
Like the sftp command, the rsync command specifies remote locations in the [user@]host:/path format.
The remote location can be either the source or the destination system, provided that one of the two machines is local.
You must be the root user on the destination system to preserve file ownership.
If the destination is remote, then authenticate as the root user.
If the destination is local, then you must run the rsync command as the root user.
In this example, synchronize the local /var/log directory to the /tmp directory on the hosta system:
[root@host ~]#rsync -av /var/log hosta:/tmproot@hosta's password:passwordreceiving incremental file list log/ log/README log/boot.log ...output omitted... sent 9,783 bytes received 290,576 bytes 85,816.86 bytes/sec total size is 11,585,690 speedup is 38.57
In the same way, the /var/log remote directory on the hosta machine synchronizes to the /tmp directory on the host machine:
[root@host ~]#rsync -av hosta:/var/log /tmproot@hosta's password:passwordreceiving incremental file list log/boot.log log/dnf.librepo.log log/dnf.log ...output omitted... sent 9,783 bytes received 290,576 bytes 85,816.86 bytes/sec total size is 11,585,690 speedup is 38.57
The following example synchronizes the contents of the /var/log directory to the /tmp directory on the same machine:
[user@host ~]$su -Password:password[root@host ~]#rsync -av /var/log /tmpreceiving incremental file list log/ log/README log/boot.log ...output omitted... log/tuned/tuned.log sent 11,592,423 bytes received 779 bytes 23,186,404.00 bytes/sec total size is 11,586,755 speedup is 1.00 [user@host ~]$ls /tmplog ssh-RLjDdarkKiW1 [user@host ~]$
Important
Correctly specifying a source directory trailing slash is important. A source directory with a trailing slash synchronizes the contents of the directory without including the directory itself. The contents are synced directly into the destination directory. Without the trailing slash, the source directory itself will sync to the destination directory. The source directory's contents are in the new subdirectory in the destination.
Bash Tab-completion automatically adds a trailing slash to directory names.
In this example, the content of the /var/log/ directory is synchronized to the /tmp directory instead of the log directory being created in the /tmp directory.
[root@host ~]#rsync -av /var/log/ /tmpsending incremental file list ./ README boot.log ...output omitted... tuned/tuned.log sent 11,592,389 bytes received 778 bytes 23,186,334.00 bytes/sec total size is 11,586,755 speedup is 1.00 [root@host ~]#ls /tmpanaconda dnf.rpm.log-20190318 private audit dnf.rpm.log-20190324 qemu-ga boot.log dnf.rpm.log-20190331 README ...output omitted...
