When to Back Up Data and What to Back Up

When to Back Up Data and What to Back Up

How often you back up your data depends upon how busy a system is and how critical the data is. A simple rule of thumb is to back up any data on the system that is irreplaceable or that someone does not want to reenter.

Root Filesystems

On most systems, the root filesystem is fairly static. You do not need to back it up as frequently as the /usr filesystem.

Changes may occur when you add software, reconfigure hardware, change the site-networking (and the system is a server or network information service [NIS] master workstation), or change some aspect of the workstation configuration. In some cases, you can maintain backups only of the individual files that change, for example, /unix, /etc/passwd, and so forth.

This process of backing up single files is not always simple. Even a minor system change such as adding a user affects files all over the system, and if you use the graphical System Manager, you may tend to forget all the files that may have changed. Also, if you are not the only administrator at the site, you may not be aware of changes made by your coworkers. Using complete filesystem backup utilities, such as the System Manager or bru, on a regular schedule avoids these problems.

A reasonable approach is to back up the root partition once a month. In addition to regular backups, here are some specific times to back up a root filesystem:

whenever you add users to the system, especially if the workstation is an NIS master workstation
just before installing new software
after installing new software and when you are certain the software is working properly

If your system is very active, or if you are not the only administrator, back up the root filesystem regularly.

User Filesystems

The /usr filesystem, which often contains both system programs (such as in /usr/bin) and user accounts, is usually more active than a root filesystem. Therefore, you should back it up more frequently.

At a typical multiuser installation, backing up once per day, using an incremental scheme, should be sufficient.

Treat the /var filesystem similarly--it contains data such as the contents of users' mailboxes.