Converting a running system to RAID 1

[AndyB78]

Hello,

I have followed the tutorial about converting a running system to RAID 1 but after copying data to the md devices, setting grub and restart I hit a kernel panic:

sda1 is boot, sda2 is root and sda3 is swap. The running system is /dev/sda.

=========
device-mapper: dm-raid45: initialized v0.2594l
Waiting for driver initialization,
Scanning and configuring dmraid supported devices
Trying to resume from LABEL=SWAP-sda3
Unable to access resume device (LABEL=SWAP-sda3)
Creating root device.
Mounting root filesystem.
mount: could not find filesystem '/dev/root'
Setting up other filesystems.
Setting up new root fs.
setuproot: moving /dev failed: No such file or directory
no fstab.sys, mounting internal defaults
setuproot: error mounting /proc: No such file or directory
setuproot: error mounting /sys: No such file or directory
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
switchroot: mount failed: No such file or directory
Kernel panic - not syncing: Attempted to kill init!
=================

I would like to mention that the only step that I missed was the "update-initramfs -u" which returned a "command not found" error I and didn't know what to replace it with.

A little help would be welcome!

Thanks and regards!

[falko]

Which distribution do you use? What's in /etc/fstab and /boot/grub/menu.lst?

[AndyB78]

Hi,

Right...sorry about that.

The distro is CentOS 5.4 / 32 bit.

[root@localhost ~]# cat /etc/fstab
/dev/md1 / ext3 defaults 0 1
/dev/md0 /boot ext3 defaults 0 2
/dev/md2 none swap sw 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0

[root@localhost ~]# cat /boot/grub/menu.lst
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/sda2
# initrd /initrd-version.img
boot=/dev/sdb
default=0
fallback 1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title RAID
root (hd1,0)
kernel /vmlinuz-2.6.18-164.el5 root=/dev/md1 ro
initrd /initrd-2.6.18-164.el5.img
savedefault
title CentOS (2.6.18-164.el5PAE)
root (hd0,0)
kernel /vmlinuz-2.6.18-164.el5PAE ro root=LABEL=/1
initrd /initrd-2.6.18-164.el5PAE.img
title CentOS-base (2.6.18-164.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-164.el5 ro root=LABEL=/1
initrd /initrd-2.6.18-164.el5.img

Thanks for replying!

Best regards!

[falko]

Please try this guide instead: http://www.howtoforge.com/how-to-set...ion-centos-5.3

The command to create a new initrd is mkinitrd on CentOS.

[AndyB78]

Quote falko
"Please try this guide instead: http://www.howtoforge.com/how-to-set...ion-centos-5.3
The command to create a new initrd is mkinitrd on CentOS."


Hi, thanks! I have tried to follow that tutorial and used mkinitrd a couple of days ago and it worked to a point. Unfortunately /dev/sda2 (the initial root partition) is indicated as "device busy" because if I put root=/dev/md1 in grub.conf on the kernel line it will throws me again "kernel panic" so I have to boot with root=LABEL=/1 in the kernel line in grub.conf. I have recompiled initrd and I believe it added raid support:

[root@localhost boot]# mkinitrd -v -f --preload=raid1 --with=raid1 /boot/initrd-2.6.18-164.el5PAE.img 2.6.18-164.el5PAE
.......
Adding module raid1
Adding module ehci-hcd
Adding module ohci-hcd
Adding module uhci-hcd
Adding module jbd
Adding module ext3
Adding module scsi_mod
Adding module sd_mod
Adding module libata
Adding module ahci
Adding module dm-mem-cache
Adding module dm-mod
Adding module dm-log
Adding module dm-region_hash
Adding module dm-message
Adding module dm-raid45

I am choosing the second option (PAE) in grub at boot time and this is my grub.conf:

[root@localhost boot]# cat grub/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/sda2
# initrd /initrd-version.img
boot=/dev/sdb
default=0
fallback 1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title RAID
root (hd1,0)
kernel /vmlinuz-2.6.18-164.el5 root=/dev/md1 ro hdb=60801,255,63
initrd /initrd-2.6.18-164.el5-2.img
savedefault
title CentOS (2.6.18-164.el5PAE)
root (hd1,0)
kernel /vmlinuz-2.6.18-164.el5PAE ro root=/dev/md1
initrd /initrd-2.6.18-164.el5PAE.img
title CentOS-base (2.6.18-164.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-164.el5 ro root=LABEL=/1
initrd /initrd-2.6.18-164.el5.img

When I boot with root=LABEL=/1 it boots normally but with root=/dev/md1 it throws me a kernel panic.

So I don't seem to be able to boot directly from a RAID mount point although I have compiled it into initrd. But if I boot from non-raid (sda2), raid is active after boot:

[root@localhost boot]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb2[1]
51199040 blocks [2/1] [_U]

md2 : active raid1 sdb3[1]
4096448 blocks [2/1] [_U]

md0 : active raid1 sdb1[1]
104320 blocks [2/1] [_U]

unused devices: <none>

I am really lost here. If you can please point me into the right direction.

Thanks!

[AndyB78]

As to "root=LABEL=/1":

[root@localhost by-label]# ls -l /dev/disk/by-label
total 0
lrwxrwxrwx 1 root root 10 Feb 11 21:10 1 -> ../../sda2

And a mount:

[root@localhost /]# mount
/dev/md1 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/md0 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)

[AndyB78]

After quite a lot of shooting in the dark I believe I have nailed it down (kind of).

When I was booting option no 1 it was giving me some error when loading X11 and it was returning me to the login form. I have tried to login on console ctrl+alt+f2 but again after entering right credentials it was redirecting me to the login form. After a little bit of googling I found out it might be due to selinux so I booted with selinux=0 and right on cue it worked. I have added sda to the raid matrix and after sync even option no 2 started to work (PAE).

So I am not sure why option no 2 was hitting a kernel panic while booting with root=/dev/md1 while option no 1 didn't...the only difference was the kernel version (normal vs PAE) which I didn't touch and the ramdisc image (which I compiled with the same options).

If anyone has any theory as to why this was happening I am more than interested to find out.

Anyway...thanks for answering Falko!