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Software RAID troubleshoot

Once, after upgrading my desktop slackware64 from 14.1 to 14.2 (with kernel upgrade too),
i be done with system, who,after lilo menu,
write “loading kernel ………………………..”

and then stops completely - nothing more.

Initial configuration was:
Intel DG965SS motherboard, core 2 duo 2.2 gHz E4500 CPU, 8 Gb RAM,
2 x 1000 Gb Seagate SATA HDD ( as sda and sdb)
dvd-writer on sata4 port

both seagate discs is partitioned as FD type ( linux autodetect raid) and 4 partitions ( mbr type) -

  • 100 Gb root (md1)
  • 2 Gb swap (md2)
  • 350 Gb /home (md3)
  • 550 Gb /Second (md4)

cat /proc/mdstat :

Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] 
md1 : active raid1 sda1[0] sdb1[1]
      104857536 blocks [2/2] [UU]
md2 : active raid1 sda2[0] sdb2[1]
      2097088 blocks [2/2] [UU]
md3 : active raid1 sda3[0] sdb3[1]
      367001536 blocks [2/2] [UU]
md4 : active raid1 sda4[0] sdb4[1]
      502805120 blocks [2/2] [UU]
unused devices: <none>

mdadm -Es :

ARRAY /dev/md1 UUID=7cc47bea:832f8260:208cdb8d:9e23b04b
ARRAY /dev/md2 UUID=cce81d3a:78965aa5:208cdb8d:9e23b04b
ARRAY /dev/md3 UUID=f0bc71fc:8467ef54:208cdb8d:9e23b04b
ARRAY /dev/md4 UUID=3f4daae2:cbf37a2a:208cdb8d:9e23b04b

# for p in 1 2 3 4; do mdadm --create /dev/md$p --name=$p --level=1 --raid-devices 2 /dev/sda$p /dev/sdb$p --metadata=0.90; done

My "fall" and "sucess" story

I have slackware64 14.1 system with raid1 on two discs.
no any mdadm.conf configuration, no any initrd -i use “huge” kernel, and all just works right.
Then i do massive system update via slackpkg update-all, including kernel update too.
check lilo.conf, restart - all looks ok. then i decide to upgrade system to 14.2 via the same slackpkg
( looks like live on macos is too boring, too predictable - all work, and so on…:D )
always, i check lilo.conf, check the new kernel is named right, have no old kernel for backup -
only one entry in lilo ( who was not good thing at all! ), and do reboot.
Then all interesting things start!!! :)

I have LiLo menu, kernel start loading…
it show lots of “…” but then all stop, and nothing more do.
That was indicated some problems with lilo updating, i suppose.
I want to boot, and re-run lilo -v
As so, i booting from Slackware64 Live CD http://bear.alienbase.nl/mirrors/slackware-live/ from AlienBob, and try mount my root partition for run lilo again.

But - there was a big problem!
there no my /dev/md1, /dev/md2, /dev/md3 and /dev/md4 after i load via slackware live CD!
and my lilo.conf was that:

# LILO configuration file
# generated by 'liloconfig'
# Start LILO global section
# Append any additional kernel parameters:
append=" vt.default_utf8=1"
boot = /dev/sda

#compact        # faster, but won't work on all systems.

# Boot BMP Image.
# Bitmap in BMP format: 640x480x8
  bitmap = /boot/slack.bmp
# Menu colors (foreground, background, shadow, highlighted
# foreground, highlighted background, highlighted shadow):
  bmp-colors = 255,0,255,0,255,0
# Location of the option table: location x, location y, number of
# columns, lines per column (max 15), "spill" (this is how many
# entries must be in the first column before the next begins to
# be used.  We don't specify it here, as there's just one column.
  bmp-table = 60,6,1,16
# Timer location x, timer location y, foreground color,
# background color, shadow color.
  bmp-timer = 65,27,0,255

# Standard menu.
# Or, you can comment out the bitmap menu above and 
# use a boot message with the standard menu:
#message = /boot/boot_message.txt

# Wait until the timeout to boot (if commented out, boot the
# first entry immediately):
# Timeout before the first entry boots.
# This is given in tenths of a second, so 600 for every minute:
timeout = 1200
# Override dangerous defaults that rewrite the partition table:
# Normal VGA console
vga = normal
# Ask for video mode at boot (time out to normal in 30s)
#vga = ask
# VESA framebuffer console @ 1024x768x64k
# VESA framebuffer console @ 1024x768x32k
# VESA framebuffer console @ 1024x768x256
# VESA framebuffer console @ 800x600x64k
# VESA framebuffer console @ 800x600x32k
# VESA framebuffer console @ 800x600x256
# VESA framebuffer console @ 640x480x64k
# VESA framebuffer console @ 640x480x32k
# VESA framebuffer console @ 640x480x256
# End LILO global section
# Linux bootable partition config begins
image = /boot/vmlinuz
  root = /dev/md1
  label = Linux
# Linux bootable partition config ends

so i do some research, do

dmesg |grep md

and from array size found out, what number was my root partition ( it was 100 gb size). it was md126.
i mount it:

mount /dev/md126 /mnt/hd

Then i run mc, and check, i was really mount there my root partition.

Then i do in console :

chroot /mnt/hd /sbin/lilo -v 3

but - lilo command end with error - it was cannot find root partition - /dev/md1.

That was problem, because now /dev/md1 was become as /dev/md126 for whatever reason.
Then, i do some reading about RAID subsystems, forums and so on, made some mistakes and experiments, who resulted on these shortcuts:

I made array assembling strings in mdadm.conf via do these comands in terminal:

mdadm -Db /dev/md127 >> /mnt/hd/etc/mdadm.conf

mdadm -Db /dev/md126 >> /mnt/hd/etc/mdadm.conf
mdadm -Db /dev/md125 >> /mnt/hd/etc/mdadm.conf
mdadm -Db /dev/md124 >> /mnt/hd/etc/mdadm.conf

In a result i get something like that in end of mdadm.conf:

ARRAY /dev/md125 metadata=0.90 UUID=7cc47bea:832f8260:208cdb8d:9e23b04b  #this one is 100 gb partition: \ (md1)
ARRAY /dev/md124 metadata=0.90 UUID=f0bc71fc:8467ef54:208cdb8d:9e23b04b  # 375 gb partition - \home - md3
ARRAY /dev/md126 metadata=0.90 UUID=3f4daae2:cbf37a2a:208cdb8d:9e23b04b  # 514 Gb partition - \Second - md4
ARRAY /dev/md127 metadata=0.90 UUID=cce81d3a:78965aa5:208cdb8d:9e23b04b  # 2 Gb partition   - swap - md2

then, based on :

dmesg | grep md

and /mnt/hd/etc/fstab i found out which md12x must be md1, md2, md3 and md4, and write it there after # as shown above.

Then i edit it to become in right way:

ARRAY /dev/md1 metadata=0.90 UUID=7cc47bea:832f8260:208cdb8d:9e23b04b
ARRAY /dev/md2 metadata=0.90 UUID=cce81d3a:78965aa5:208cdb8d:9e23b04b
ARRAY /dev/md3 metadata=0.90 UUID=f0bc71fc:8467ef54:208cdb8d:9e23b04b
ARRAY /dev/md4 metadata=0.90 UUID=3f4daae2:cbf37a2a:208cdb8d:9e23b04b

also i wrote in mdadm.conf that string, just to be sure, hostname do not affect raid naming:

HOMEHOST <ignore>

then i made mdadm_stop_127.scr script:

echo "stopping md127"
mdadm --stop /dev/md127
echo "stopping md126"
mdadm --stop /dev/md126
echo "stopping md125"
mdadm --stop /dev/md125
echo "stopping md124"
mdadm --stop /dev/md124
##mdadm --assemble --scan

I copy it to livesystem root, copy also my edited mdadm.conf from /mnt/hd/etc/mdadm.conf to livesystem /etc, and umount /dev/md125 !

And then i run it - my mdadm_stop_127.scr

I see, all that arrays be stopped, and then i run:

mdadm -As

then i see

cat /proc/mdstat

I see, all my RAID become as it must be - /dev/md1, md2, md3, and md4!

then i do mount my root hdd again:

mount /dev/md1  /mnt/hd

and do:

chroot /mnt/hd /sbin/lilo -v 3

all looks good. i do restart:

shutdown -r now 

( or press ctrl +alt+ del)

after restart i see, system start loading, and went after previously dead point. i get to login screen, log in as root, and see, there is md1 ( root) and md2 ( swap), but no md3 and md4 ( instead of it i have these /home and /Second arrays as md125 and md124).

Thats look very strange and unlogical, as all raid arrays var create about same time, and was similar - but half of it get right numbers, and half - not. now i try different thing - disable raid autodetect on kernel, before root fs is mounted, and mdadm.conf is available for md module:

i restart machine, press tab on LiLo prompt, and use kernel parameters:

Linux raid=noautodetect md=1,/dev/sda1,/dev/sdb1

that says kernel not to autodetect raid arrays, but assemble md1 raid ( md=1) from /dev/sda1 and /dev/sdb1 partition, because without root kernel system cant start.
as i load system in that way, all looks right - there was /dev/md1, md2, md3 and md4.
then i just do system restart, without any kernel parameters, and all again going to be right - md1 till md4.
looks like, system writes something in RAID arrays superblock, or metadata, or something like that, about previously gived md name, because, if not, after restart i must get again situation as previously - with md1, md2, md125 and ,d124…

that was, in a most, all of story. yet, there is some another workarounds of that situation.

Workarounds for incorrect raid devices naming

  1. 1. Using UUID in lilo ( i do not check this), and in fstab for mounting partitions.

do a

ls /dev/disk/by-uuid/

or better, go in that location with midnight commander, and youl see, there is a “files” named as numbers - that was the raid array disk uuid - and symlink to /dev/mdx.

for automate info feed into fstab you can use this way:

cd /dev/disk/by-uuid

ls -d -l $PWD/* >> /etc/fstab

after that you must immediately edit /etc/fstab and make in a right way, otherwise you may have problems with mounting in next boot…

/dev/md2         swap             swap        defaults         0   0
/dev/md1         /                ext4        defaults         1   1
##/dev/md3         /home            ext4        defaults         1   2
/dev/disk/by-uuid/ef92814a-2db1-4d47-8d70-4c5a8d56e287   /home            ext4        defaults         1   2
/dev/md4         /Second          ext4        defaults         1   2
#/dev/cdrom      /mnt/cdrom       auto        noauto,owner,ro,comment=x-gvfs-show 0   0
/dev/fd0         /mnt/floppy      auto        noauto,owner     0   0
devpts           /dev/pts         devpts      gid=5,mode=620   0   0
proc             /proc            proc        defaults         0   0
tmpfs            /dev/shm         tmpfs       defaults         0   0
take a note! disk UUID by


and that one, who you get via

mdadm -D
mdadm -Db
mdadm -Es

differ, not the same!!! in fstab ( lilo too?) you must use UID from /dev/disk/by-uuid/ !

  1. 2. Using initramd.
# mkinitrd_command_generator.sh revision 1.45
# This script will now make a recommendation about the command to use
# in case you require an initrd image to boot a kernel that does not
# have support for your storage or root filesystem built in
# (such as the Slackware 'generic' kernels').
# A suitable 'mkinitrd' command will be:


mkinitrd -c -k 3.2.29 -f ext4 -r /dev/md1 -m mbcache:jbd2:ext4 -R -u -o /boot/initrd.gz

rightly edited mdadm.conf then must be copied in/boot/tree??? before you run this mkinitrd conf.

after you run that mkinitrd, you must update lilo.

Useful commands in this case

show raid array info:

mdadm -Es

Assemble RAID array based on mdadm.conf

mdadm -As

show array info:

mdadm -D /dev/md127

show defined array another info:

mdadm -Db /dev/md127

show scsi devices info:


show assembled raid arrays status:

cat /proc/mdstat

show UUID info about discs ( or RAID arrays) in system:

ls /dev/disk/by-uuid/
dmesg |grep md

re-run lilo, when booted from another source.

chroot /mnt/hd /sbin/lilo -v 3

stop named RAID array:

mdadm --stop /dev/md127

kernel options:

$kernelname raid=noautodetect md=1, /dev/sda1,/dev/sdb1

turn on not to autodetect RAID arrays, and define raid array /dev/md1, from two partitions ( members? )

Useful Links:


Originally written by — John Ciemgals 2016/11/28 04:50

Rewrited with used materials from “Links” and LinuxQuestions.org Slackware forum, especially user bassmadrigal and bormant from linux.org.ru help — John Ciemgals 2016/11/28 09:15

 howtos:misc:software_raid_troubleshoot_howto ()