Certification Objective 2.06: Filesystems

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By default, the RHEL installation program configures multiple volumes-separate volumes associated with different directories. The advantage of separate partitions for certain directories is that it limits the risks to your system. For example, many Webmasters configure their Web sites to write daily log files with data relating to all users who visit their sites. These files can become quite large, especially for large online merchants.

Before you decide how to set up partitions, you need to know about each of the major Linux directories. Linux directories are organized according to something known as the Filesystem Hierarchy Standard (FHS).

Filesystem Hierarchy Standard

The FHS is a standard for organizing directories for Linux- and Unix-based systems. Every FHS-compliant operating system starts with a top directory, root, symbolized by the forward slash. All other directories are subdirectories of root. The major FHS directories are described in Table 1-1 in Chapter 1.

Why Separate Filesystems?

Unix was developed when disk space was miniscule by today's standards. As Unix became an operating system for larger companies and universities, administrators had access to multiple, separate physical disks for each Unix computer. They took advantage of the space by splitting up the filesystem into smaller, more manageable pieces. Different directories were mounted on different physical drives.

This has a number of advantages. Smaller partitions are easier to maintain. Smaller partitions are easier to back up and restore. The size of a partition can limit the space taken by any specific directory. You can set up specific partitions as 'read-only' for additional security.

There is at least one case where you should not mount different Linux directories on different partitions. If you're limited to a smaller hard drive, you need all of the spare room that you can get. This may apply to an older laptop computer, or an older computer that you're using for a dedicated purpose, such as a DNS server or a gateway router.

Configuring Linux Filesystems on Different Partitions

When you set up an RHEL Server filesystem, you can let Red Hat configure the partitions for you. By default, Red Hat configures a root directory (/) and a /boot directory partition.

Additional filesystems can be mounted on separate partitions to meet additional or specific needs of related groups of users. Some examples include: /home, /usr, /var, /development, /dbms, /financials, /inventory. The /tmp directory is often also mounted on a separate partition, to limit the space allocated to what should be temporary storage.

Exam Watch 

As befits a standard Linux server, it's quite possible that you'll need to configure several filesystems on different partitions during the Installation and Configuration exam.

Other Possible Separate Filesystems

Dedicated services are also good candidates for separate filesystems. For example, specific applications such as Web and FTP services can take up gigabytes of data. They store files in the /var/www/html and /var/ftp/pub directories.

You want to protect the rest of your computer if problems arise with a specific service. File and print sharing services such as NFS and Samba present security risks because they expose shared directories to other users. If you don't mount these services on separate partitions, anyone who uploads a large number of files could conceivably fill your hard disk.

If the number of files and users are large, you may even want to spread shared files over several partitions on different physical drives. In this situation, not every user will want data from the same drive all of the time. The load is shared by the different drives. Performance is improved.

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