5.10.13. Other tools for the ext2/ext3 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 percent, which on most disks isn't enough to be wasteful. However, for floppies there is no point in reserving any blocks.
  

See the tune2fs manual page for more information.
dumpe2fs shows information about an ext2 or ext3 filesystem, mostly from the superblock. Below is a sample output. Some of the information in the output is technical and requires understanding of how the filesystem works, but much of it is readily understandable even for lay-admins.

   

#dumpe2fsdumpe2fs 1.32 (09-Nov-2002) Filesystem volume name: / Last mounted on: not available Filesystem UUID: 51603f82-68f3-4ae7-a755-b777ff9dc739 Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal filetype needs_recovery sparse_super Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 3482976 Block count: 6960153 Reserved block count: 348007 Free blocks: 3873525 Free inodes: 3136573 First block: 0 Block size: 4096 Fragment size: 4096 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 16352 Inode blocks per group: 511 Filesystem created: Tue Aug 26 08:11:55 2003 Last mount time: Mon Dec 22 08:23:12 2003 Last write time: Mon Dec 22 08:23:12 2003 Mount count: 3 Maximum mount count: -1 Last checked: Mon Nov 3 11:27:38 2003 Check interval: 0 (none) Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 128 Journal UUID: none Journal inode: 8 Journal device: 0x0000 First orphan inode: 655612 Group 0: (Blocks 0-32767) Primary superblock at 0, Group descriptors at 1-2 Block bitmap at 3 (+3), Inode bitmap at 4 (+4) Block bitmap at 3 (+3), Inode bitmap at 4 (+4) Inode table at 5-515 (+5) 3734 free blocks, 16338 free inodes, 2 directories

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 Section 12.1 for more information on

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