Mount Partitions to Restore Backups
I've been asking myself what do I do if a partition
gets corrupted? Yeah, I do dumps regularly to another
disk, but when you boot from an OpenBSD install cd
there's no matching /dev/wd1d there. There are no
devices with wd1, only wd0. There's MAKEDEV but it
says that the operation isn't permitted when I type
./MAKEDEV wd1d. What's going on here? I don't have
to worry about being root, this is an installation
cd. Actually I've shelled out of the install routine.
Let's do ls -l and see what we get. I'll be darned,
MAKEDEV is not executable. chmod +x MAKEDEV
and that solves that problem.
Once again, I type ./MAKEDEV wd1d and hit enter.
This time there's no error message. Another quick
ls -l shows all kinds of wd1 listings now including
wd1d. Now I mount -r /dev/wd1d /mnt and no error
message. Let's see what mount shows. Cool, wd1d is
mounted. I do a ls -l on it and sure enough, there's
my /data partition on the hard drive where all the
dumps are stored.
Now if a partition gets corrupted, all I have to do
is boot up on the cd, make the device, run newfs on
the corrupted partition, mount the partition with
the backups on it as shown above, mount the newly
formatted partition in write mode, change directory
into it and restore the appropriate dump.
Life is good!
Someone may say you don't need the cd to boot from,
you just boot the bsd.rd kernel, and that's okay,
that is if your / partition isn't the corrupted
one. Also, remember, restore is in /sbin. I don't
think there's anything wrong with using the cd to
work from. That is, unless you didn't install off
a cd and don't have one. I think it's a good idea
to keep one one hand.
This is probably kindergarden stuff for most of the
guys on the OpenBSD mailing list, but for me it's
like when the apple hit old Isaac on the head! It's
a revelation! ;) I'm putting this up here in hopes
someday some poor newbie having the same problem
googles around and finds it. That'd be cool.
Everytime I do a fresh install of OpenBSD, I create
a wd1a partition on a 2nd hard drive the same size
as my root partition on the primary hard drive and
label it altroot. In root's crontab, right below my
env settings SHELL, PATH, and HOME, I enter
ROOTBACKUP=1. That way, every day the system will
backup /root to /altroot. Alternately, you can edit
/etc/daily.local and enter the same ROOTBACKUP=1
line.
In either case, you also have to remember to enter
the partition info in /etc/fstab. The format is a
little different too, than the format the others
partitions use: /dev/wd1a /altroot ffs xx 0 0
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