I'm looking for a way to have a system with disposable storage that can be
rebooted and all filesystem changes are thrown away. After reboot, the system
starts with a fresh root volume again. The use case is for automated testing.
We run test scripts that could potentially not clean up after themselves.
This is almost like stateless, but the storage is local to the system (not
iSCSI, NFS or NBB).
1. Install Fedora 13 using default partition layout
NOTE: modify the layout to leave extra room in the LVM volume group
2. Apply attached patch
3. Update grub.conf to enable dracut LVM snapshot support. Add the following
boot arguments
rd_LVM_SNAPSHOT=vg_test1055/lv_snap (note the VG name will depend on your
system).
rd_LVM_SNAPSIZE= (optional, defaults to size of volume specified with by
rd_LVM_SNAPSHOT)
4. Adjust grub.conf and fstab to use LVM snapshot
$ sed -i -e 's|lv_root|lv_snap|' /boot/grub/grub.conf
$ sed -i -e 's|lv_root|lv_snap|' /etc/fstab
5. Reboot system
Expected results (no value provided for rd_LVM_SNAPSIZE):
dracut: Starting plymouth daemon
dracut: rd_NO_DM: removing DM RAID activation
dracut: rd_NO_MD: removing MD RAID activation
dracut: Removing existing LVM snapshot vg_test1055/lv_snap
dracut: Logical volume "lv_snap" successfully removed
dracut: No LVM snapshot size provided, using size of vg_test1055/lv_root (
9024.00m)
dracut: Creating LVM snapshot vg_test1055/lv_snap ( 9024.00m)
dracut: Logical volume "lv_snap" created
dracut: Scanning devices sda2 for LVM logical volumes vg_test1055/lv_root
vg_test1055/lv_swap
dracut: inactive Original '/dev/vg_test1055/lv_root' [8.81 GiB] inherit
dracut: inactive '/dev/vg_test1055/lv_swap' [1.00 GiB] inherit
dracut: inactive Snapshot '/dev/vg_test1055/lv_snap' [8.81 GiB] inherit
dracut: Mounted root filesystem /dev/mapper/vg_test1055-lv_snap
dracut: Loading SELinux policy
dracut: Switching root
Expected results (rd_LVM_SNAPSIZE=100m):
dracut: Starting plymouth daemon
dracut: rd_NO_DM: removing DM RAID activation
dracut: rd_NO_MD: removing MD RAID activation
dracut: Removing existing LVM snapshot vg_test1055/lv_snap
dracut: Logical volume "lv_snap" successfully removed
dracut: Creating LVM snapshot vg_test1055/lv_snap (100m )
dracut: Rounding up size to full physical extent 128.00 MiB
dracut: Logical volume "lv_snap" created
dracut: Scanning devices sda2 for LVM logical volumes vg_test1055/lv_root
vg_test1055/lv_swap
dracut: inactive Original '/dev/vg_test1055/lv_root' [8.81 GiB] inherit
dracut: inactive '/dev/vg_test1055/lv_swap' [1.00 GiB] inherit
dracut: inactive Snapshot '/dev/vg_test1055/lv_snap' [128.00 MiB] inherit
dracut: Mounted root filesystem /dev/mapper/vg_test1055-lv_snap
dracut: Loading SELinux policy
dracut: Switching root
lvchange and vgchange '--monitor n' will not prevent lvm from
attempting to dlopen the libdevmapper-event library.
dracut git commit 47ab3b6c5e introduced the use of '--monitor n' but
'--ignoremonitoring' is needed now that the libdevmapper-event library
isn't copied into the initramfs (ever since 0fae59d6eb)
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
- the use of sed is placeholder "hack" until lvm2 provides a proper
tool for changing lvm.conf
- lvm_scan.sh should run lvm commands with --ignorelockingfailure to
re-use lvm's existing initrd-specific logic; future lvm2 changes
will split this flag out into various new command-line switches
- no monitoring should be started from within initramfs
- NOTE: the same should apply to 90dmraid/install
- the correct types would be: '[ "blkext", 1 , "cciss0", 16 ]'
but lvm2 (>= 2.02.52) already properly supports both 'blkext' and
'cciss' (including cciss0 -> cciss7)
LVM
rd_NO_LVM
disable LVM detection
rd_LVM_VG=<volume group name>
only activate the volume groups with the given name
crypto LUKS
rd_NO_LUKS
disable crypto LUKS detection
rd_LUKS_UUID=<luks uuid>
only activate the LUKS partitions with the given UUID
MD
rd_NO_MD
disable MD RAID detection
rd_MD_UUID=<md uuid>
only activate the raid sets with the given UUID
DMRAID
rd_NO_DM
disable DM RAID detection
rd_DM_UUID=<dmraid uuid>
only activate the raid sets with the given UUID
init now has the following points to inject scripts:
/cmdline/*.sh
scripts for command line parsing
/pre-udev/*.sh
scripts to run before udev is started
/pre-trigger/*.sh
scripts to run before the main udev trigger is pulled
/initqueue/*.sh
runs in parallel to the udev trigger
Udev events can add scripts here with /sbin/initqueue.
If /sbin/initqueue is called with the "--onetime" option, the script
will be removed after it was run.
If /initqueue/work is created and udev >= 143 then this loop can
process the jobs in parallel to the udevtrigger.
If the udev queue is empty and no root device is found or no root
filesystem was mounted, the user will be dropped to a shell after
a timeout.
Scripts can remove themselves from the initqueue by "rm $job".
/pre-mount/*.sh
scripts to run before the root filesystem is mounted
NFS is an exception, because it has no device node to be created
and mounts in the udev events
/mount/*.sh
scripts to mount the root filesystem
NFS is an exception, because it has no device node to be created
and mounts in the udev events
If the udev queue is empty and no root device is found or no root
filesystem was mounted, the user will be dropped to a shell after
a timeout.
/pre-pivot/*.sh
scripts to run before the real init is executed and the initramfs
disappears
All processes started before should be killed here.
The behaviour of the dmraid module demonstrates how to use the new
mechanism. If it detects a device which is part of a raidmember from a
udev rule, it installs a job to scan for dmraid devices, if the udev
queue is empty. After a scan, it removes itsself from the queue.
Harald Hoyer