Other tools for the ext2 filesystem

In addition to the filesystem creator (mke2fs ) and checker (e2fsck ) accessible directly or via the filesystem type independent front ends, the ext2 filesystem has some additional tools that can be useful.

tune2fs  adjusts filesystem parameters. Some of the more interesting parameters are:

• A maximal mount count. e2fsck  enforces a check when filesystem has been mounted too many times, even if the clean flag is set. For a system that is used for developing or testing the system, it might be a good idea to reduce this limit.
• A maximal time between checks. e2fsck  can also enforce a maximal time between two checks, even if the clean flag is set, and the filesystem hasn't been mounted very often. This can be disabled, however.
• Number of blocks reserved for root. Ext2 reserves some blocks for root so that if the filesystem fills up, it is still possible to do system administration without having to delete anything. The reserved amount is by default 5%, which on most disks isn't enough to be wasteful. However, for floppies there is no point in reserving any blocks.

dumpe2fs  shows information about an ext2 filesystem, mostly from the superblock. Figure 4.5 shows a sample output. Some of the information in the output is technical and requires understanding of how the filesystem works (see appendix ), but much of it is readily understandable even for layadmins.

  
Figure 4.5: Sample output from dumpe2fs 

debugfs  is a filesystem debugger. It allows direct access to the filesystem data structures stored on disk and can thus be used to repair a disk that is so broken that fsck  can't fix it automatically. It has also been known to be used to recover deleted files. However, debugfs  very much requires that you understand what you're doing; a failure to understand can destroy all your data.

dump  and restore  can be used to back up an ext2 filesystem. They are ext2 specific versions of the traditional UNIX backup tools. See chapter 10 for more information on backups.