lvm: support for dynamic LVM SNAPSHOT root volume
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