LVM Snapshot
lvmdiskscan
pvs -o+pv_used
lsblk
lvcreate --size 3G --snapshot --name storage_snapshot /dev/storage/website
lvdisplay /dev/storage/website
mkfs.ext4 /dev/storage/storage_snapshot
mkdir /storage_data/websitesnapshot
mount /dev/storage/storage_snapshot /storage_data/websitesnapshot
e2label /dev/storage/storage_snapshot "Web Snapshot"
lvs
Preparing to Create an LVM Snapshots
An LVM snapshot has to be created in the same Volume Group as the source LV. Using CoW (Copy on Write) Technology the underlying storage has to be the same. Allowing unchanged data in the snapshot to be read from the original LV source. Our Volume Group is full, so we will delete the existing Logical Volume and recreate it a a smaller size. We will also use two mountpoints, /mnt/original and /mnt/snap.
# umount /mnt
# mkdir /mnt/{original,snap}
# lvremove /dev/vg1/lv1
# lvcreate -n lv1 -L 600m vg1
# mkfs.ext4 /dev/vg1/lv1
# mount /dev/vg1/lv1 /mnt/original
After....
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
umount /mnt/volume1
Deactivate and activate you volume:
# lvchange -a n /dev/volume_group/volume1
# lvchange -a y /dev/volume_group/volume1
mount /dev/volume_group/volume1 /mnt/volume1
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
lvmdiskscan
/dev/centos7/root [ 9.31 GiB]
/dev/vda1 [ 953.00 MiB]
/dev/centos7/swap [ <2.80 GiB]
/dev/vda2 [ 22.37 GiB] LVM physical volume
/dev/centos7/home [ 956.00 MiB]
/dev/centos7/storage_snapshot [ <4.66 GiB]
/dev/centos7/storage_cache [ <4.66 GiB]
/dev/vdb [ 13.00 GiB]
6 disks
1 partition
0 LVM physical volume whole disks
1 LVM physical volume
pvs -o+pv_used
PV VG Fmt Attr PSize PFree Used
/dev/vda2 centos7 lvm2 a-- <22.37g 12.00m <22.36g
lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 252:0 0 25G 0 disk
├─vda1 252:1 0 953M 0 part /boot
└─vda2 252:2 0 22.4G 0 part
├─centos7-root 253:0 0 9.3G 0 lvm /
├─centos7-swap 253:1 0 2.8G 0 lvm [SWAP]
├─centos7-home 253:2 0 956M 0 lvm /home
├─centos7-storage_snapshot 253:3 0 4.7G 0 lvm /storage/snapshot
└─centos7-storage_cache 253:4 0 4.7G 0 lvm /storage/cache
vdb 252:16 0 13G 0 disk
umount /storage/snapshot
lvremove /dev/centos7/storage_snapshot
lvcreate --size 4.6G --snapshot --name storage_snapshot /dev/centos7/root
Rounding up size to full physical extent 4.60 GiB
Logical volume "storage_snapshot" created.
lvdisplay /dev/centos7/root
--- Logical volume ---
LV Path /dev/centos7/root
LV Name root
VG Name centos7
LV UUID tyxhHd-HZ5n-AaNN-mA5q-3nMr-Uh5c-dZNUj7
LV Write Access read/write
LV Creation host, time localhost, 2019-03-29 19:03:26 +0000
LV snapshot status source of
storage_snapshot [active]
LV Status available
# open 1
LV Size 9.31 GiB
Current LE 2384
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
home centos7 -wi-ao---- 956.00m
root centos7 owi-aos--- 9.31g
storage_cache centos7 -wi-ao---- <4.66g
storage_snapshot centos7 swi-aos--- 4.60g root 0.02
swap centos7 -wi-ao---- <2.80g
df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/centos7-root ext4 9.1G 1.8G 6.9G 21% /
devtmpfs devtmpfs 484M 0 484M 0% /dev
tmpfs tmpfs 496M 0 496M 0% /dev/shm
tmpfs tmpfs 496M 6.8M 489M 2% /run
tmpfs tmpfs 496M 0 496M 0% /sys/fs/cgroup
/dev/vda1 ext4 922M 105M 754M 13% /boot
/dev/mapper/centos7-storage_cache ext4 4.5G 19M 4.2G 1% /storage/cache
/dev/mapper/centos7-home xfs 953M 33M 921M 4% /home
tmpfs tmpfs 100M 0 100M 0% /run/user/0
/dev/mapper/centos7-storage_snapshot ext4 9.1G 1.8G 6.9G 21% /storage/snapshot
df -aTh {check, whether SNAPSHOT was mounted}| /etc/mtab | /proc/mounts
Filesystem Type Size Used Avail Use% Mounted on
rootfs - - - - - /
sysfs sysfs 0 0 0 - /sys
proc proc 0 0 0 - /proc
devtmpfs devtmpfs 484M 0 484M 0% /dev
securityfs securityfs 0 0 0 - /sys/kernel/security
tmpfs tmpfs 496M 0 496M 0% /dev/shm
devpts devpts 0 0 0 - /dev/pts
tmpfs tmpfs 496M 6.8M 489M 2% /run
tmpfs tmpfs 496M 0 496M 0% /sys/fs/cgroup
cgroup cgroup 0 0 0 - /sys/fs/cgroup/systemd
pstore pstore 0 0 0 - /sys/fs/pstore
cgroup cgroup 0 0 0 - /sys/fs/cgroup/memory
cgroup cgroup 0 0 0 - /sys/fs/cgroup/cpu,cpuacct
cgroup cgroup 0 0 0 - /sys/fs/cgroup/perf_event
cgroup cgroup 0 0 0 - /sys/fs/cgroup/cpuset
cgroup cgroup 0 0 0 - /sys/fs/cgroup/net_cls,net_prio
cgroup cgroup 0 0 0 - /sys/fs/cgroup/devices
cgroup cgroup 0 0 0 - /sys/fs/cgroup/pids
cgroup cgroup 0 0 0 - /sys/fs/cgroup/freezer
cgroup cgroup 0 0 0 - /sys/fs/cgroup/hugetlb
cgroup cgroup 0 0 0 - /sys/fs/cgroup/blkio
configfs configfs 0 0 0 - /sys/kernel/config
/dev/mapper/centos7-root ext4 9.1G 1.8G 6.9G 21% /
selinuxfs selinuxfs 0 0 0 - /sys/fs/selinux
systemd-1 autofs 0 0 0 - /proc/sys/fs/binfmt_misc
hugetlbfs hugetlbfs 0 0 0 - /dev/hugepages
mqueue mqueue 0 0 0 - /dev/mqueue
debugfs debugfs 0 0 0 - /sys/kernel/debug
/dev/vda1 ext4 922M 105M 754M 13% /boot
/dev/mapper/centos7-storage_cache ext4 4.5G 19M 4.2G 1% /storage/cache
/dev/mapper/centos7-home xfs 953M 33M 921M 4% /home
tmpfs tmpfs 100M 0 100M 0% /run/user/0
/dev/mapper/centos7-storage_snapshot ext4 9.1G 1.8G 6.9G 21% /storage/snapshot
lvs -o name,lv_ancestors,lv_descendants centos7
LV Ancestors Descendants
home
root storage_snapshot
storage_cache
storage_snapshot root
swap
RECOVERING SNAPSHOT
umount /storage/snapshot
df -h {verify}
lvconvert --merge /dev/centos7/storage_snapshot
Falko Timme' method:
mkdir /backups
tar -pczf /backups/root.tar.gz /storage/snapshot
And if you like to do a bitwise backup (i.e. an image), you can do it like this:
dd if=/dev/centos7/storage_snapshot of=/backups/root.ddserver1:~# dd if=/dev/centos7/storage_snapshot of=/backups/root.dd
19513344+0 records in
19513344+0 records out
9990832128 bytes (10 GB) copied, 320.059 seconds, 31.2 MB/s
umount /storage/snapshot
lvremove /dev/centos7/storage_snapshot
That's it, you've just made your first backup from an LVM snapshot.
Restore A Backup
This chapter is about restoring the /dev/centos7/root volume from the dd image we've created in the previous chapter. Normally you can restore a backup from the same running system if the volume that you want to restore doesn't contain system-critical files. But because the /dev/centos7/root volume is the system partition of our machine, we must use a rescue system or Live-CD to restore the backup. The rescue system/Live-CD must support LVM.
To restore the /dev/centos7/root volume, I boot the system from the Debian Etch Netinstall CD and type in rescue at the boot prompt: