Ext2文件系统在操作系统崩溃或者非法关机的情况下重启之后，要开始漫长的自检过程。自检的时间大致和硬盘的大小有关。因此，现在大部分LINUX系统在安装的时候都使用了Ext3。但如果使用了Ext2文件系统，又不想重装系统的话，可以采用下面提供的方法将Ext2转换为Ext3。
本人已经验证了文中提到的ext2转换到ext3的方法。具体见正文的标注。
Converting Ext2 Filesystems to
Ext3
by Steve Litt
[ | | | ]
Contents:
Executive Summary
Until recently, the Ext2 filesystem has been the Linux default. Ext2
is a technological miracle. Low fragmentation, redundant enough to be
reliably regenerated on error yet diskspace efficient, fast, and
adaptable. But when the computer is rebooted or powered off without
correctly shutting down, Ext2 filesystems are placed in an error state.
When the computer comes back up, the user is confronted with some mildly
confusing, and very intimidating, messages and choices. Should he let
the filesystem correct itself? Warning, this can lose data!
Journalized filesystems are made to eliminate such error messages.
The Ext3 filesystem is an Ext2 filesystem with a journal file and some
filesystem driver additions making the filesystem journalized.
My research and those of others, as well as limited experimentation
by myself, indicate that the tune2fs -j command, which is the primary
command for converting from Ext2 to Ext3, is safe to run even on
writeable mounted partitions. However, when possible, I run the command
on unmounted or read-only mounted partitions. It might be
superstitious, but I feel that is playing it safe. Nevertheless, when
confronted with situations making unmounting difficult, I run the
command on writeable mounted partitions.
Converting the root directory from Ext2 to Ext3 is a little more
difficult. Converting back from Ext3 to Ext2 is a hairy and dangerous
procedure. Instructions for both are given in this document, but think
long and hard before converting the root directory.
Disclaimer
Obviously, you use this document at your own risk. I am not
responsible for any damage or injury caused by your use of this
document, or caused by errors and/or omissions in this document. If
that's not acceptable to you, you may not use this document. By using
this document you are accepting this disclaimer.
The conversion procedure is simple enough. Imagine /dev/hda10
mounted as /test – the procedure would be as follows:
- Log in as root
- Make sure /etc/fstab
has /dev/hda10 mounted to /test as ext2, read write
- umount /dev/hda10
- If you can't unmount it, then
remount it read only (mount -o remount,ro /dev/hda10)
- tune2fs -j /dev/hda10
- Edit /etc/fstab,
and for /dev/hda10, change
ext2 to ext3
- mount /dev/hda10
- /sbin/shutdown -h now
- mount | grep /dev/hda10
- If it's not shown as ext3, reboot, if still not, troubleshoot
- Otherwise, you're done.
A few explanations are in order. The tunefs command creates the
journal file, which is kept in a special inode on the device (by
default). You then must change the /etc/fstab
entry to reflect it's a journalling filesystem, and then mount it.
Converting the /usr directory
This applies only to those systems in which the
/usr tree has its own partition.
Converting the
/usr
directory presents a challenge because commands like tune2fs are located
in the /usr tree, so it must be mounted. Mount it read only with the
following command:
mount -o remount,ro /usr
Then run
tune2fs -j, edit
/etc/fstab, and then unmount
and remount
/usr.
Converting the / directory
First, think long and hard before deciding to convert the root
directory. Ext3's primary purpose is shorter recovery from disaster
rather than data loss prevention. Converting the root directory from
Ext2 to Ext3 isn't difficult, but converting it back from Ext3 to Ext2
is a treacherous process fraught with problems. But, if you really must
perform the Ext2 to Ext3 conversion on the root directory, here's how,
assuming
/dev/hda2 is
mounted as the root directory and
/dev/hda1
is mounted as
/boot:
- Log in as root
- Edit /etc/fstab and
change ext2 to ext3 on the line referencing the
root directory. /*这里仅指出需要修改的是根目录，也就是fstab文件中/boot一行对应的ext2是不需要修改的*/
- tune2fs -j /dev/hda2
- cd /boot
- mv initrd-2.4.18-26.8.0.img initrd-2.4.18-26.8.0.img.ext2
- mkinitrd
initrd-2.4.18-26.8.0.img 2.4.18-26.8.0
- reboot
In the preceding, you MUST perform all the steps, including the
mkinitrd, before rebooting.
Failing to perform all the steps before rebooting produces a "buried
shovel" where if only you could boot the machine, you could run the
mkinitrd command, and if only
you could run the
mkinitrd
command, you could boot the machine.
笔者验证了本小节提到的将根目录（/）从ext2转换为ext3。完全按照本小节讲解的方法在RH 9上实现，重启后可以正常进入系统。如果需要永久性的关闭当系统非法关机后启动时的硬盘检测的话，可以再进入系统后，执行命令：
tune2fs -c 0 device
其中device即为你想避免自检的分区，我这里/dev/hda1挂载在/下，/dev/hda2挂载在/boot。两个都需要关闭检测的话，可以：
tune2fs -c 0 /dev/hda1
tune2fs -c 0 /dev/hda2
如果要设置隔多长时间检测一次的话，可以使用:
tune2fs -i interval device
这里不再举例，具体的使用方法见tune2fs。
There may come a time when you want to convert back to Ext2. For
directories other than the root directory or /usr, it's pretty easy. The
following once again uses the example of /dev/hda10 mounted to directory /test:
The root directory is a challenge for a number of reasons. First, it
must be mounted for the system to run, but it must be unmounted to run
the e2fsck command. Also,
different distros behave different ways. The mkinitrd command varies widely
between distros. The preceding works on a Red Hat 8.0 machine, but
other machines might require other solutions. We'll assume that /dev/hda1 is /boot, while /dev/hda2 is the root directory (/).
Assume that /usr is
mounted by /dev/hda4
Summary
Converting from Ext2 to Ext3 is usually easy, although converting the
root partition is usually undesirable. From what I hear, and from my
limited testing, the
tune2fs -j
command is so safe that it can be performed on a partition mounted
read-write. However, it's usually easy to unmount the partition or
mount it read-only, and when that's easy, I've done it that way.
Changing the filesystem type of the root directory requires rebuilding
the initrd image. Those procedures are explained in this document.
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