Create system snapshots with CYA

System Saver

© Lead Image © ssilver, 123RF.com

© Lead Image © ssilver, 123RF.com

Article from Issue 214/2018
Author(s):

The CYA script helps you back up system files, which you can then restore quickly in case of an emergency.

It is always surprising how many users skip regular backups. This negligence can hit you hard when least expected. Backup software generally backs up directories, partitions, or an entire installation.

Some backup tools are used to back up and restore the operating system itself, not the user data. CYA, for instance, is an 80KB Bash script based on rsync that lets the user keep a copy of the system close at hand. CYA stands for "Cover Your Ass(ets)" – I think we all get the gist. CYA does not try to overload you with a graphical interface; instead, it lets you start the backup with a single command – or even automatically.

Versatile

According to the developer, the CYA script, which was developed by Cyberweb Solutions, can create snapshots of any Linux or BSD distribution – and theoretically, even of any system that offers Bash and rsync. CYA understands how to handle most Linux filesystems, including ZFS and Btrfs. The software is licensed under a BSD license, so anyone can view and modify the code for their own use. You can run CYA automatically with systemd or cron or integrate it into scripts.

The way CYA works is similar to restore points in Microsoft's System Restore, which also only backs up the operating system itself without user data. You can reset the system to an earlier status using a restore point. CYA offers the same features. The home directory remains untouched – at least so far. In the latest version, the software saves the user's data separately with the cya mydata function.

By default, the program automatically or manually creates three snapshots; then, it overwrites the oldest one. You can also tell CYA to create snapshots that it does not overwrite or that do not even appear in the list of backups.

The software backs up without compression or a proprietary format by default, which means that you can easily restore not only the entire installation, but also individual files or directories if required. You do not actually need the cya restore function; in principle, a file manager or a tool for the terminal is sufficient.

What Installation?

Because the software is a script, you don't need to install CYA in the classic way. Just download it as a ZIP archive [1], which you then unpack, then copy the cya file to the bin directory under your home directory or the usr/local/bin directory. If you want to put the cya script somewhere else, add the path to the $PATH variable. Be sure to set the file permissions to make the file executable.

The script is now ready for use. The only other requirement is that the system is configured to use sudo [2]. Once you have done this, make sure you are in the home directory and execute the cya command (Figure 1). If nothing happens, log out and back on again – but this should not be necessary for most distributions.

Figure 1: During the first run, CYA creates the new user named cya and its infrastructure.

As you can see, the program creates a new user named cya, as well as some directories and files. Snapshots will end up in points/ in the future. The cya.conf file is still empty – you can store your own configuration options here. The LAST_RUN file tells you when the software last ran.

The cya help call reveals all the options and parameters you can use to control CYA (see Table 1). The default settings are fine for many use cases; however, you might want to familiarize yourself with the available options to have the right commands at hand when in doubt.

Table 1

CYA Commands

Command

Results

Create Snapshots

save

Create snapshot (rotating)

keep

Create manual snapshot (no rotation)

mydata

Back up your home directory

archive

Manually archive snapshot

Recovery

restore

Restore data

Other

configfile

Help for manual configuration

directories

List directories to be backed up

list

List snapshots you have created

remove

Remove manual snapshots

script

Linux mount script

uses

Use cases for script integration

version

Update check

Configuration

Type cya configfile to configure. Examples of modifying the configuration are shown here. If you need a rotation setup with more than three slots, you can change MAX_SAVES="" and write this statement and all the others to the empty cya.conf file in /home/cya/. You can then add or exclude files and directories until the result is what you want. The sequence is irrelevant.

Once you have completed the configuration, start the first backup. Simply enter cya save in the terminal (Figure 2). The script then saves the system except for /home/. CYA stores the snapshot in the home directory of the cya user created by the system under the points/ directory.

Figure 2: During the first snapshot, the software implements the configuration you have created. The backed up data is stored in the points/ directory.

If the home directory is on a separate partition and you use the automatic method, you must make sure there is enough free space for at least four backups. This number results from the fact that the program keeps three snapshots each for the automatic method and then rotates.

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