Using rsync to Sync Local and Remote Systems
rsync is a utility commonly found on Linux operating systems and is a remote and local file synchronization tool. rsync stands for remote sync. The rsync algorithm is used to minimize network usage by only moving portions of files that have changed.
This tutorial will take you through the following:
Basic rsync Usage
To begin, we will create two directories and some test files with the following commands:
cd ~
mkdir liquid
mkdir web
touch liquid/file{1..100}Now we have a directory called liquid with 100 empty files in it.
You can see it with this command:
ls liquid file1 file18 file27 file36 file45 file54 file63 file72 file81 file90 file10 file19 file28 file37 file46 file55 file64 file73 file82 file91 file100 file2 file29 file38 file47 file56 file65 file74 file83 file92 file11 file20 file3 file39 file48 file57 file66 file75 file84 file93 file12 file21 file30 file4 file49 file58 file67 file76 file85 file94 file13 file22 file31 file40 file5 file59 file68 file77 file86 file95 file14 file23 file32 file41 file50 file6 file69 file78 file87 file96 file15 file24 file33 file42 file51 file60 file7 file79 file88 file97 file16 file25 file34 file43 file52 file61 file70 file8 file89 file98 file17 file26 file35 file44 file53 file62 file71 file80 file9 file99
There is also still an empty directory called web.
You can use rsync to copy all the files from /liquid over to /web:
rsync -r liquid/ web
The -r command means recursive, which is needed for directory syncing.
You could also use the -a flag instead of the -r flag:
rsync -a liquid/ web
-a stands for archive, it syncs recursively and preservers symbolic links, special and device files, modification times, group, owner and permissions. It is more commonly used than -r and is usually what you should use.
Note: |
You may have noticed the trailing slash (/) at the end of the first argument in the above example. This is necessary to mean “the contents of liquid”. Without using the trailing slash, the directory liquid would be placed within the directory web. |
Without the trailing slash, the hierarchy will look like:
-/web/liquid/[files]
Make sure you double-check your arguments before executing your rsync command.
You can use the -n or –dry-run command to double-check your output, to get the appropriate output, use the -v (-verbose) flag together with -a and -n. It will look like this:
rsync -anv liquid/ web sending incremental file list ./ file1 file10 file100 file11 file12 file13 file14 file15 file16 file17 file18 . . .
In comparison, removing the trailing slash will result in this output:
rsync -anv liquid web sending incremental file list liquid/ liquid/file1 liquid/file10 liquid/file100 liquid/file11 liquid/file12 liquid/file13 liquid/file14 liquid/file15 liquid/file16 liquid/file17 liquid/file18 . . .
You can see here how the directory itself was transferred.
Remote Transfers Made Simple
The true power of rsync is in its ability to perform remote transfers. Remote-to-local or local-to-remote file transfers can be made easier with the use of SSH keys. With SSH keys set up on both remote and local servers, synchronization can be scripted effortlessly and without having to enter a password every time. Find out how to set-up an SSH key in our article Setting Up and Using SSH Keys.
If you’ve used scp before, the syntax for remote transfers is similar:
rsync [flags] [local path] [user] @ [remote server] : {remote path}As an example, an rsync using this syntax would look like the following:
rsync -a ~/liquid root@remote_host:/web
This is called a “push” operation because it pushes the directory from the local system to the remote system.
The opposite operation is “pull”. It is used to sync the remote directory to a local system. If the directory liquid were on a remote system, the syntax would be:
rsync -a username@remote_host:/home/username/liquid place_to_sync_on_local_machine
The source is always the first argument, the destination is always the second.
Note: |
The colon (:) between the remote server and the remote path is required for both push and pull operations. |
Alternate SSH Ports
If you have changed the SSH port on your server, you will need to tell rsync to use the new port number. If you want to learn how to change the SSH port, see our article Changing Your SSH Port with the Command Line.
Example with a normal SSH port:
rsync -azh /local/path/file user@host.com:/remote/path/file
Example with alternate SSH port:
rsync -azh /local/path/file -e 'ssh -p 22334' user@host.com:/remote/path/file
More about rsync
Mastering rsync allows you to design complex backup operations and have fine-tuned control over what is transferred and how. The flexibility of rsync makes a good option for many different file-level operations. For more information about flags and rsync commands, see our article, Exploring the rsync Utility.
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