Posted by: Xjlittle
dumpe2fs, ext2, ext3, journaling file system, linux file system, tune2fs
Linux has the capability to use a large number of file systems. Generally you will find the ext3 file system on the Red Hat style operating system as the default.
The ext3 file system is a journaling file system. Journaling is process by which a file system logs changes to the file system during disk writing so that a corruption causing event such as a power outage will allow the data to be reconstructed so that the writes can be cleanly written to the disk.
tune2fs command is used to tune the ext3 file system. You can set parameters such as maximum mount count and different behaviors when an error is detected by the kernel on the file system.
The maximum mount count for an ext3 file system is set to 20 by default. To set the mount count to 0, which is useful when using the Red Hat Cluster Manager, you would issue the following command:
tune2fs -c 0 /dev/hda1
The file system has three error modes when the kernel detects an error on the file system. These are:
>continue Continues normally
>remount-ro Remounts the file system read-only ready to fsck
>panic Causes the kernel to panic which stops the system. This is not recommended unless you are a system tester.
An ext3 file has a reserved percentage setting. This is space that is only available to the root user. The root user can also associate this space with a system group. This is done with the -g option:
tune2fs -g admins /dev/hda2
To check your file system parameters use the dumpe2fs command:
[root@centos5-lt ~]# dumpe2fs -h /dev/mapper/laptop-root
dumpe2fs 1.39 (29-May-2006)
Filesystem volume name:
Last mounted on:
Filesystem UUID: c5167029-83e6-488a-98fa-400cc7932191
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 5124480
Block count: 5120000
Reserved block count: 256000
Free blocks: 637276
Free inodes: 4805027
You can read about setting many more parameters for your ext3 file system by reviewing the man page “man tune2fs”.