Is there any way to change the "File System" filed in /etc/fstab every time it boots?

cricketlong · 04-06-2011, 04:06 AM

I install my LFS6.3 on a removable disk, it works well now but a defect annoys me, every time it boots my root file system is recognize as /dev/sdb1 on my computer, however, it would not be so lucky to be recognized as /dev/sdb1 meanwhile the "File System" field in /etc/fstab in always /dev/sdb1. So, is there any way to change the "File System" filed in /etc/fstab every time it boots?
Any solution would be appreciated by any people being confused by this defect.

jschiwal · 04-06-2011, 04:15 AM

You can use the device ID, the UUID of the filesystem, or the LABEL in /etc/fstab instead of the device node in the first column of fstab. The manpage of fstab should provide the details.

The device nodes can be determined looking at the links in /dev/disk/by-*/ directories.
The UUID can also be determined using "sudo /sbin/blkid <device-node>".

You can also use sudo "/sbin/udevadm info --query all --name <device-node>" to obtain all of the names I mentioned above.

Use an appropriate ID also in grub's menu.lst file as well so that if the device node changes, grub knows which device is root, and where the kernel is, and where the second stage drivers are. This will be needed before /etc/fstab can be read.

cricketlong · 04-06-2011, 05:01 AM

thanx, jschiwal. The UUID in /etc/fstab was recognized meanwhile the same string(I copied from /etc/fstab to menu.lst) of UUID in menu.lst was recognized as unknown device, here is my menu.lst:

# Begin /boot/grub/menu.lst

# By default boot the first menu entry.
default 0

# Allow 30 seconds before booting the default.
timeout 10

# Use prettier colors.
color green/black light-green/black

# The first entry is for LFS.
title LFS 6.3
root (hd0,0)
kernel /boot/lfskernel-2.6.22.5 ro root=UUID=bc02d4f0-3368-47d9-b862-c55149586d09 rootdelay=8

jschiwal · 04-07-2011, 04:56 AM

The form of your kernel line may be wrong. You can use "UUID=<uuid>" in the fstab file, but grub may parse the info in the kernel line differently.

Here is my menu.lst stanza:

Code:

title Desktop -- openSUSE 11.4 - 2.6.37.1-1.2
    root (hd1,0)
    kernel /vmlinuz-2.6.37.1-1.2-desktop root=/dev/disk/by-id/ata-TOSHIBA_MK2049GSY_48CYT01OT-part6 resume=/dev/disk/by-id/ata-WDC_WD3200BEKT-00F3T0_WD-WXC0A8966517-part2 splash=silent quiet showopts vga=0x317
    initrd /initrd-2.6.37.1-1.2-desktop

You could use /dev/disk/by-uuid/... instead if you wish. Or simple use "ls /dev/disk/by-id/*" to see which /by-id/ link to use instead.