Because EXT2 and EXT3 filesystems share the same internal structure (with the exception of whether or not a journal exists), you can easily convert an existing EXT2 filesystem to an EXT3 filesystem to take advantage of the journaling capabilities of the latter. You may want to do this if you decided to play things safe and created all of your filesystems as EXT2 filesystems when you installed SUSE on your system, or if you are upgrading an older, existing Linux system that uses EXT2 filesystems to the latest revision of SUSE Linux. Either way, converting an existing EXT2 filesystem to EXT3 is a painless operation involving two steps: using the tune2fs command to add an EXT3 journal to each existing EXT2 filesystem that you want to upgrade and then updating your system's filesystem table (/etc/fstab) to identify the upgraded partition(s) as EXT3 filesystems rather than EXT2 filesystems. The structure of the /etc/fstab file is explained in detail later in this chapter in the section "Mounting Filesystems Automatically." Upgrading an EXT2 filesystem to an EXT3 filesystem is a completely safe operation to perform on any existing EXT2 filesystem. The EXT3 filesystem was designed with this sort of upgrade in mind and is a truly impressive piece of work.
As mentioned earlier, you should not upgrade EXT2 filesystems to EXT3 filesystems in certain circumstances, specifically if your EXT2 filesystem holds data files such as Oracle database files that have their own built-in journaling mechanism. Running two journaling mechanisms on the same file may cause data corruption or may cause your database system to crash.
Listing 3-8 shows the output from using the tune2fs command to upgrade an existing EXT2 filesystem to an EXT3 filesystem. When this command completes, simply bring up the file /etc/fstab in your favorite text editor, search for the line related to each partition that you upgraded, and change the value ext2 to ext3. After saving the file, you can reboot your system to take advantage of the journaling capabilities of your new EXT3 filesystems.
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