mirror of
https://github.com/linux-apfs/apfstests.git
synced 2026-05-01 15:01:44 -07:00
Nathan Scott
152 lines
5.1 KiB
Plaintext
152 lines
5.1 KiB
Plaintext
############
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# xfscrash # crash testing setup for XFS
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############
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*** disclaimers ***
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work-in-progress, buyer-beware, your-mileage-may-vary, this-is-a-hack
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*** what xfscrash does ***
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xfscrash allows realistic testing of XFS log recovery and XFS check/repair
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by generating log activity on an XFS partition, then rebooting the machine
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at a random point. When the machine comes back up, xfscrash is restarted
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and then tests either the log recovery or xfs_repair on the dirtied
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filesystem. All going well the process continues.
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*** getting ready for crash testing ***
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Most filesystems (ext2 included) can't withstand having the machine
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they're running on rebooted while they're active. So the crash test
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machine needs to have all filesystems other than the test FS mounted
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read-only so they won't get trashed when the machine reboots.
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*** mouting FSes read-only ***
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Following is a recipe for making a redhat linux (6.2) machine with a single
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ext2 FS mounted on root able to be booted read-only. Your Mileage May
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Vary - don't try this on an important machine.
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The idea is to move anything that needs to be r/w into the /initrd_init
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directory, replacing the moved directories with links to the moved ones.
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That way the /initrd_init directory may be copied to a ramdisk, and
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mounted over /initrd on the root FS which never gets remounted r/w.
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# go to single user
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init 1
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# make a mount point for the ramdisk
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mkdir /initrd
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# link across to the /initrd_init directory for when
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# the ramdisk isn't mounted
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ln -s /initrd_init/dev .
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ln -s /initrd_init/etc .
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ln -s /initrd_init/proc .
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ln -s /initrd_init/sbin .
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ln -s /initrd_init/tmp .
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ln -s /initrd_init/var .
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# make the /initrd_init directory
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mkdir /initrd_init
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cd /initrd_init
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# move /dev
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mv /dev .
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ln -s /dev /initrd/dev
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# move /etc
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mv /etc .
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ln -s /etc /initrd/etc
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# make proc mount
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mkdir proc
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# move /tmp
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mkdir tmp
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rm -rf /tmp
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ln -s /tmp /initrd/tmp
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# link /sbin
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ln -s /sbin .
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# setup a tree for parts of /var
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mkdir var var/cache var/lock var/lock/console var/lock/subsys
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mkdir var/log var/preserve var/run
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touch /var/run/utmp /var/log/utmp /var/log/wtmp
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# move parts of /var
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rm -rf /var/cache /var/lock /var/log /var/preserve /var/run
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ln -s /initrd/var/cache /var/cache
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ln -s /initrd/var/lock /var/lock
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ln -s /initrd/var/log /var/log
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ln -s /initrd/var/preserve /var/preserve
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ln -s /initrd/var/run /var/run
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# make a mount for /var/shm
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mkdir var/shm
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ln -s /var/shm /initrd/var/shm
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# move /var/spool
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mkdir var/spool
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mkdir var/spool/mail var/spool/anacron var/spool/at var/spool/lpd
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mkdir var/spool/rwho var/spool/mqueue var/spool/cron
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rm -rf /var/spool
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ln -s /var/spool /initrd/var/spool
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# move /var/tmp
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mkdir var/tmp
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rm -rf /var/tmp
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ln -s /var/tmp /initrd/var/tmp
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# trim /dev - too many inodes here - remove anything you don't need
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# (small ramdisk has a small number of inodes)
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rm -rf /initrd/dev/<....>
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All going well, all the directories you've made should link through
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/initrd and into /initrd_init, and the machine should come back up
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if you restart it.
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You want to keep the contents of /initrd_init to a minimum because
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this stuff has to fit into the ramdisk.
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*** getting the ramdisk going ***
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See the rc.sysinit file for some details of what to do to get the
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ro-root/ramdisk up and running.
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Once everything is going, the root FS should never be remounted to
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r/w on boot and should be in r/o mode when the machine comes up.
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All going well, any open files have been redirected through the
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symlinks onto the ramdisk, so you should be able to remount the
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root FS to r/w and then remount it back to r/o.
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Since there's no r/w filesystems mounted, it should be ok to
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reboot the machine with 'reboot -fn' and everything should come
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back without dirty filesystems and without having to fsck.
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*** starting xfscrash ***
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The simplest way to restart xfscrash on reboot is to start it
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in the background from rc.local. The script logs to /dev/tty1,
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/dev/console & a logfile by default, so the output should be
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easy to find.
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Link the xfscrash directory off an NFS mounted FS so you can make
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changes while the machine is rebooting and so you can touch the
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'stop' and 'start' control files.
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To configure the system, change the parameters in the configuration
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section of the 'xfscrash' script.
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To start the system, touch the 'start' control file and then either
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reboot or manually run the 'xfscrash' script.
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To stop the system, touch the 'stop' control file and wait for the
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next cycle to start when the control file will be checked and
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the test terminated.
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