I recently had the need to get a file from a snapshot on a device which had very little local storage. Rather than using the process from White Paper - Extracting a file from a GAIA Snapshot, I decided to mount the snapshot directly and get the file from there. Thought others here might be interested in the process.
First, you need to find the snapshot's node in the /dev virtual filesystem. Use 'lvdisplay'. Each logical volume will have an entry like this:
[Expert@DallasSA]# lvdisplay
...
--- Logical volume ---
LV Path /dev/vg_splat/lv_DemoSnap
LV Name lv_DemoSnap
VG Name vg_splat
LV UUID 7TbELE-hYY0-9fLi-1F3y-K3MN-0AlH-octYt7
LV Write Access read/write
LV Creation host, time DallasSA, 2022-04-12 16:16:55 +0000
LV Status available
# open 0
LV Size 14.44 GiB
Current LE 462
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:4
...
Create a directory, and mount the snapshot:
[Expert@DallasSA]# mkdir /mnt/snapshot
[Expert@DallasSA]# ls -lh /mnt/snapshot
total 0
[Expert@DallasSA]# mount -o ro /dev/vg_splat/lv_DemoSnap /mnt/snapshot
[Expert@DallasSA]# mount
/dev/mapper/vg_splat-lv_current on / type xfs (rw,inode32)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
/dev/mapper/vg_splat-lv_log on /var/log type xfs (rw,inode32)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
cgroup on /sys/fs/cgroup type tmpfs (rw,uid=0,gid=0,mode=0755)
/dev/mapper/vg_splat-lv_DemoSnap on /mnt/snapshot type xfs (ro)
[Expert@DallasSA]# ls -lh /mnt/snapshot/
total 48M
-rw-rw---- 1 admin root 0 Nov 20 15:33 1
-rw-r--r-- 1 admin root 0 Dec 29 16:07 DEBUG
drwxr-xr-x 2 admin root 85 Nov 20 15:17 DOCS
-rw-r--r-- 1 admin root 542 Oct 17 2020 License.txt
lrwxrwxrwx 1 admin root 7 Apr 12 16:17 bin -> usr/bin
...
The '-o ro' argument in the mount command makes it read-only so you don't accidentally change something in the snapshot. With that, you now have read-only access to the whole system as it was when the snapshot was taken.
Edit: Added some newlines between the output of one command and the next command to make the output easier to follow visually.
