Have you
ever deleted a logical volume by accident? Can you recover it looking
into the backups? Well, the answer is YES. For those who are not
familiar with Logical Volume Management (LVM) is a device mapper target that provides logical volume management for the Linux kernel.- Wikipedia. It
is an abstraction layer or software that has been placed on top of your
hard drive for flexible manipulation of the disk space. Some of the
articles published in the past on LVM are:
- Add and Extend disk on Virtual Box through LVM
- Move your /home to a new LVM partition
- Part 1 on Managing LVM with PVMOVE
- Part2 on Managing LVM with PVMOVE
- Ansible playbook to configure LVM
All
test carried out on this blog post have been tested on a CentOS
machine. Please don't make a live test on a production server.
1. So, as you can see below I have an lv called lvopt which is from a vg called centos.
2. Same is mounted on the /opt
3. There are some data in that partition as well:
4. I created a directory inside the /opt directory
5.
Now, let's pretend to remove the lvm lvopt. Or say, someone did it by
accident because it was unmounted. The command lvremove will be used
here to remove the lv. Note: that the lv need to be unmounted.
6.
If you make an lvs, lvdisplay or vgs or even mount again the partition,
you cannot do it. The data is lost. But you can still recover it. This
is because the lvm contains the archive of your lv inside the folder
/etc/lvm/archive. But, you cannot read the files directly.
7.
But you can still, interpret part of the files. Since we deleted the
volume group called "centos", we knew that it is referenced in the file
centos_... The question that arises here is which file is relevant for
you. Right? So to understand which archive you want to restore, you need
to use the command vgcfgrestore --list <name of volume group>.
Here is an example:
8.
If you observe carefully, each archive has been backup at a certain
time. In my case, I deleted the LV on 18-Apr-2019 at 11:17:17 2019:
9.
So, I want to restore from that last archive. You will need to copy the
full patch of the vg file. In my case it is
/etc/lvm/archive/centos_00004-1870674349.vg. The goal here is to restore
the lv before this specific time, or simply restore back the lv before
the command lvremove was fired. Here is the command:
10. If you launch the command lvs, you will notice the presence of the lv.
11.
But, mounting back the lv won't result in anything. This is because the
lv is inactive. You can see it with the command lvscan. Please take
note below that the lvopt is inactive.
12. To activate it you simply need to use the command lvchange.
13. Mount it back and you are done.
I
believe this can be very useful especially when you have encountered a
situation where someone deleted an lv. I hope you enjoy this blog post.
Please share and comment below if you like it.
