Solaris Troubleshooting : Restore SDS Root mirror from the backup

NOTE: In order to restore the machine exactly the way it was, it is necessary to have a record of the locations of the state databases, and also the configuration of the metadevices. These are *not* held in user-readable form on the root filesystem, so it is useful to get the information BEFORE a crash with the commands


# metadb -i
This command shows the condition and location of DiskSuite’s state database replicas. It is useful to have this information in case their recreation is necessary.

 # metastat -p

You will redirect this output to a file for safekeeping. This information is most often sent to the /etc/opt/SUNWmd/md.tab file for disaster recovery purposes (see step 6 below). Check the md.tab file prior to overwriting it, though. If a valid one exists, redirect the metastat -p to another filename and run a ‘diff’ on it to check for inconsistencies.The metastat -p, however, will reflect the most current, known, configuration. Of course, you will need to create a new root disk and restore the last full backup to that new disk. It is expected that you will partition the disk in much the same manner as you had it before.  

Remember that if there was a small partition on your original disk for a state replica that you do the same thing for this disk. Once the disk has been created, restore your root filesystems from backups. However, before attempting to boot the system after the restore, we must make some necessary changes to let Solaris know that the root disk is no longer mirrored. To do this, the /etc/system and the /etc/vfstab files must be modified.

1) Boot cdrom, and mount the root filesystem to /a.

ok boot cdrom -s
# mount /dev/dsk/c#t#d#s# /a

2) Restore the root filesystem from backup tape into /a and initialize the boot block using

# installboot /usr/platform/<arch>/lib/fs/ufs/bootblk /dev/rdsk/c#t#d#s#

3) Mount and restore any other critical filesystems such as /usr /var /opt etc.

4) If the replacement machine does not have it disks connected via the same paths as the original then you may have to follow the procedure documented in SRDB 15010 to rebuild the /devices and /dev structures.

5) vi /a/etc/system (before using vi you may need to set the terminal type e.g. TERM=sun; export TERM)

Remove ALL lines between the “MDD root info” lines as well as those between the “MDD database info” lines. In the following example file, all these lines would be removed from the file:

————————————————————-
* Begin MDD root info (do not edit)
forceload: misc/md_trans

forceload: misc/md_raid
forceload: misc/md_hotspares
forceload: misc/md_stripe
forceload: misc/md_mirror
forceload: drv/sd
forceload: drv/esp
forceload: drv/espdma
forceload: drv/sbus
forceload: drv/iommu
rootdev:/pseudo/md@0:0,3,blk
* End MDD root info (do not edit)* Begin MDD database info (do not edit)
set md:mddb_bootlist1=”sd:14:16 sd:15:16″
* End MDD database info (do not edit)
————————————————————-

6) vi /a/etc/vfstab

Change all metadevices for the root filesystems (root, usr, var, and opt) back to regular slices (/dev/dsk/c#t#d#s#). Comment out all the other metadevices for the time being. For example:

** EXAMPLE FILE BEFORE:
—————————————————————————
#device device mount FS fsck mount mount
#to mount to fsck point type pass at boot options
/proc – /proc proc – no –
fd – /dev/fd fd – no –
swap – /tmp tmpfs – yes –
/dev/md/dsk/d1 – – swap – no –
/dev/md/dsk/d0 /dev/md/rdsk/d0 / ufs 1 no –
/dev/md/dsk/d2 /dev/md/rdsk/d2 /usr ufs 1 no –
/dev/md/dsk/d3 /dev/md/rdsk/d3 /var ufs 2 yes –
/dev/md/dsk/d4 /dev/md/rdsk/d4 /opt ufs 2 yes –
/dev/md/dsk/d5 /dev/md/rdsk/d5 /export/home ufs 3 yes quota
/dev/md/dsk/d6 /dev/md/rdsk/d6 /export/home1 ufs 3 yes quota

—————————————————————————

** EXAMPLE FILE AFTER:
—————————————————————————
#device device mount FS fsck mount mount
#to mount to fsck point type pass at boot options
#
/proc – /proc proc – no –
fd – /dev/fd fd – no –
swap – /tmp tmpfs – yes –

/dev/dsk/c0t0d0s1 – – swap – no –
/dev/dsk/c0t0d0s0 /dev/rdsk/c0t0d0s0 / ufs 1 no –
/dev/dsk/c0t0d0s6 /dev/rdsk/c0t0d0s6 /usr ufs 1 no –
/dev/dsk/c0t0d0s7 /dev/rdsk/c0t0d0s7 /var ufs 2 yes –
/dev/dsk/c0t0d0s4 /dev/rdsk/c0t0d0s4 /opt ufs 2 yes –
#/dev/md/dsk/d5 /dev/md/rdsk/d5 /export/home ufs 3 yes quota
#/dev/md/dsk/d6 /dev/md/rdsk/d6 /export/home1 ufs 3 yes quota
—————————————————————————

7) Remove all lines (except for the 2 comment lines at the top) from the “mddb.cf” file. This file exists either in the /etc/opt/SUNWmd or /etc/lvm directory, depending on the version of DiskSuite you are running.

8 ) Boot the system from the newly restored boot disk. When the system comes up, only root (and /usr, /var, and /opt, if they exist) will be mounted using the slices on the new root disk.

 9) Re-add the state databases with the ‘metadb’ command. Use the output of the ‘metadb’ command you saved to get the locations.

metadb -a -f <location1>
metadb -a -f <location2>
metadb -a -f <location3>

10) Recreate the “md.tab” file from the ‘metastat’ output you saved (or from memory), except make sure that all mirrors to be one-way mirrors and all RAID5 devices contain the “-k” option. For the boot disk, ensure that the one-way mirrors refer to the side which has been restored. Make sure the order is correct so that mirrors aren’t created until the submirrors already exist. See below the necessary changes that must be made to ensure one-way mirrors are used.

The “md.tab” file exists either in the /etc/opt/SUNWmd or /etc/lvm directory, depending on the version of DiskSuite you are running.



For example:

vi md.tab

** EXAMPLE FILE BEFORE:
————————————————-
d0 -m d10 d20 <– see the two-way mirror!
d10 1 1 c0t0d0s0
d20 1 1 c1t0d0s0
d1 -m d11 d21
d11 1 1 c0t0d0s1
d21 1 1 c1t0d0s1
d2 -m d12 d22
d12 1 1 c0t0d0s6
d22 1 1 c1t0d0s6
d3 -m d13 d23
d13 1 1 c0t0d0s7
d23 1 1 c1t0d0s7
d4 -m d14 d24
d14 1 1 c0t0d0s4
d24 1 1 c1t0d0s4
d5 -m d15 d25
d15 4 c0t1d0s2 c0t2d0s2 c1t1d0s2 c1t2d0s2
d25 4 c0t3d0s2 c1t3d0s2 c1t4d0s2 c1t5d0s2
d6 -r c1t6d0s2 c1t8d0s2 c1t9d0s2
————————————————-

** EXAMPLE FILE AFTER:
————————————————-
d10 1 1 c0t0d0s0
d20 1 1 c1t0d0s0
d0 -m d10 <– see the one-way mirror!
d11 1 1 c0t0d0s1
d21 1 1 c1t0d0s1
d1 -m d11
d12 1 1 c0t0d0s6
d22 1 1 c1t0d0s6
d2 -m d12
d13 1 1 c0t0d0s7
d23 1 1 c1t0d0s7
d3 -m d13
d14 1 1 c0t0d0s4
d24 1 1 c1t0d0s4
d4 -m d14
d15 4 c0t1d0s2 c0t2d0s2 c1t1d0s2 c1t2d0s2
d25 4 c0t3d0s2 c1t3d0s2 c1t4d0s2 c1t5d0s2
d5 -m d15
d6 -r c1t6d0s2 c1t8d0s2 c1t9d0s2 -k
————————————————-

11) Run the ‘metainit’ command to create all the metadevices that are listed in the “md.tab” file.

# metainit -f -a

12) Run the ‘metaroot’ command to set the metadevice as a root device.

# metaroot d0

13) Add in the other metadevices into the /etc/vfstab file for the other root filesystems as well as the other metadevices that you created in step 7.

14) Reboot.

15) You will now attach all the second mirrors to all the mirrored metadevices. For example:
# metattach d0 d20


Ramdev

Ramdev

I have started unixadminschool.com ( aka gurkulindia.com) in 2009 as my own personal reference blog, and later sometime i have realized that my leanings might be helpful for other unixadmins if I manage my knowledge-base in more user friendly format. And the result is today's' unixadminschool.com. You can connect me at - https://www.linkedin.com/in/unixadminschool/

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