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---
title: "Fixing an error I made a few years ago and migrating to LVM"
date: 2025-09-21
slug: migrate-to-lvm
status:
tags:
- linux
- disks
- partitions
- lvm
- debian
- blog
- homelab
- storage
description: "Migrating a live Linux system to LVM with no reinstall and no data loss. Past-me forgot one checkbox and present-me is paying for it."
category: system
---
<h2><strong>History</strong></h2>
<p>A few years ago when I decided to go down the rabbit-hole of homelabbing, one of the first thing I did was a debian12-template.
Smart choice would you say :</p>
<ul>
<li>a perfect virtual machine that would be optimized</li>
<li>configured like I wanted and needed (ssh keys, proxy &amp; dns setup, ip settings, etc...)</li>
<li>and an homogeneous fleet of VMs</li>
</ul>
<p>Great, so now I can simply clone the template over and over for every need I have, right ? Right... ? Except for the simple fact that when I created the debian12-template, I made a mistake that i've to correct now : I did <strong>not</strong> use LVM.</p>
<h2><strong>Partitioning choices</strong></h2>
<p>When you create a linux virtual machine, there's a step called <strong>partitioning</strong> (there are a few steps before : <em>language choice</em>, <em>keyboard language</em>, <em>network configuration</em>, <em>root password</em>, <em>first user setup</em> and then the <strong>partitioning</strong> step)</p>
<p><img src="../img/disksetup.png" alt="Image description" /></p>
<p>We have 4 choices :</p>
<ul>
<li>Guided and using full disk (less flexible but quick and easy. To choose if you are sure you will <strong>never</strong> need to expand the partition)</li>
<li>Guided and using full disk with LVM (flexible, you get logical volumes which gives you the ability to resize disks easily) </li>
<li>Guided and using full disk with encrypted LVM (same as the previous one but encrypted with LUKS. More secure but need entering a password at every boot, which we don't want since we would have to pass on every VM every host reboot)</li>
<li>Manual (you get full control, you can do whatever you want, but then need more knowledge)</li>
</ul>
<p>So the thing is, what choices do I have if I ever decided not to use LVM for <strong>every</strong>.<strong>single</strong>.<strong>vm</strong> in my homelab because of the mistake I made with the debian12-template a few years ago ?</p>
<p>To my knowledge, there's only 2 way : either restart everything from scratch or try to migrate every vm partitions' to a LVM one. Considering the lack of time, motivation and documentation I currently have, restart everything from scratch is off the table.</p>
<h2><strong>Current installation</strong></h2>
<p>Let's assess what we currently have on our fresh debian12 installation :</p>
<pre><code class="language-shell">root@debian:~# cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 12 (bookworm)"</code></pre>
<p>I've installed docker and a few packages, to run a container called <a href="https://github.com/louislam/uptime-kuma">uptime-kuma</a> just to see if it still works after migrating with curl.</p>
<pre><code class="language-shell">root@debian:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a5fec5ba4df5 louislam/uptime-kuma:1 "/usr/bin/dumb-init …" 2 minutes ago Up 2 minutes (healthy) 0.0.0.0:3001-&gt;3001/tcp, :::3001-&gt;3001/tcp uptime-kuma</code></pre>
<pre><code class="language-shell">root@debian:~# curl localhost:3001
Found. Redirecting to /dashboardroot@debian:~#</code></pre>
<p>For the disks and current partitioning :</p>
<pre><code class="language-shell">root@debian:~# fdisk -l
Disk /dev/sda: 5 GiB, 5368709120 bytes, 10485760 sectors
Disk model: QEMU HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x3563c74a
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 8484863 8482816 4G 83 Linux
/dev/sda2 8486910 10483711 1996802 975M 5 Extended
/dev/sda5 8486912 10483711 1996800 975M 82 Linux swap / Solaris</code></pre>
<pre><code class="language-shell">root@debian:~# df -h | grep /dev
udev 965M 0 965M 0% /dev
/dev/sda1 4.0G 2.6G 1.2G 69% /
tmpfs 984M 0 984M 0% /dev/shm</code></pre>
<p>So let's try to migrate our freshly installed debian 12 virtual machine </p>
<h2><strong> Migration</strong></h2>
<p><strong>/!\ Before anything, create a snapshot or a backup ! /!\</strong></p>
<p>First thing first, we do need another disk so we have <em>somewhere</em> to migrate <em>to</em> :)
Adding a disk on Proxmox is quite easy. Just go to the VM configuration and select the option to add another disk.
<img src="../img/vmhardwareadddisk.png" alt="Image description" />
<img src="../img/vmadddisk.png" alt="Image description" /></p>
<p>We should now see the new virtual disk we've just added :</p>
<pre><code class="language-shell">root@debian:~# fdisk -l
Disk /dev/sdb: 5 GiB, 5368709120 bytes, 10485760 sectors
Disk model: QEMU HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/sda: 5 GiB, 5368709120 bytes, 10485760 sectors
Disk model: QEMU HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x3563c74a
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 8484863 8482816 4G 83 Linux
/dev/sda2 8486910 10483711 1996802 975M 5 Extended
/dev/sda5 8486912 10483711 1996800 975M 82 Linux swap / Solaris</code></pre>
<p>Now we want to partition the new disk, with fdisk : </p>
<ul>
<li><strong>n</strong> for a new partition</li>
<li><strong>p</strong> for a primary type</li>
<li><strong>default</strong> for the partition number (press enter to get the default choice)</li>
<li><strong>default</strong> for the first sector (press enter to get the default choice)</li>
<li><strong>default</strong> for the last sector (press enter to get the default choice)</li>
<li><strong>t</strong> to select a type</li>
<li><strong>8e</strong> to chose LVM type</li>
<li><strong>a</strong> to make it bootable</li>
<li><strong>w</strong> to save and apply (and exit)</li>
</ul>
<pre><code class="language-shell">root@debian:~# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.38.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Device does not contain a recognized partition table.
Created a new DOS (MBR) disklabel with disk identifier 0x931446ee.
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1):
First sector (2048-10485759, default 2048):
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-10485759, default 10485759):
Created a new partition 1 of type 'Linux' and of size 5 GiB.
Command (m for help): t
Selected partition 1
Hex code or alias (type L to list all): 8e
Changed type of partition 'Linux' to 'Linux LVM'.
Command (m for help): a
Selected partition 1
The bootable flag on partition 1 is enabled now.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.</code></pre>
<p><em>Little tip for Linux: most of the time, when you’re prompted to make a choice and one option is in <strong>capital letters</strong>, it indicates the <strong>default choice</strong> that will be used if you just press Enter.</em></p>
<p>So now, our disk <em>/dev/sdb</em> has a partition (which we can check with <code>fdisk -l /dev/sdb</code> :</p>
<pre><code class="language-shell">root@debian:~# fdisk -l /dev/sdb
Disk /dev/sdb: 5 GiB, 5368709120 bytes, 10485760 sectors
Disk model: QEMU HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x931446ee
Device Boot Start End Sectors Size Id Type
/dev/sdb1 * 2048 10485759 10483712 5G 8e Linux LVM</code></pre>
<p>We can now install a few packages that will help us to transfer files, use LVM and extend our partition size.
<code>apt update &amp;&amp; apt install lvm2 rsync parted -y</code></p>
<p>Now that <code>lvm2</code> is installed, we have to :</p>
<ul>
<li>create a physical volume with <strong>pvcreate</strong>. It is the LVM equivalent of a disk or partition. This tells LVM to use the partition /dev/sdb1 as part of its storage pool.</li>
<li>create a volume group with <strong>vgcreate</strong>. It's like a box that will hold your logical volumes.</li>
<li>create a logical volume for both the root and the swap with <strong>lvcreate</strong>. It's the partitions you'll use and resize if needed.</li>
</ul>
<pre><code class="language-shell">root@debian:~# pvcreate /dev/sdb1
Physical volume "/dev/sdb1" successfully created.
root@debian:~# vgcreate vg-system /dev/sdb1
Volume group "vg-system" successfully created
root@debian:~# lvcreate -L 1G -n lv-swap vg-system
Logical volume "lv-swap" created.
root@debian:~# lvcreate -l 100%FREE -n lv-root vg-system
Logical volume "lv-root" created.</code></pre>
<p>We can then use the <code>mkfs.ext4</code> command to format the logical volume lv-root to ext4. And with <code>mkswap</code> we can set up the lv-swap as... <em>swap</em> (who would've guessed, right ?)</p>
<pre><code class="language-shell">root@debian:~# mkfs.ext4 /dev/vg-system/lv-root
mke2fs 1.47.0 (5-Feb-2023)
Discarding device blocks: done
Creating filesystem with 1047552 4k blocks and 262144 inodes
Filesystem UUID: 73265d61-1c37-4362-8298-c54e2488baa9
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done</code></pre>
<pre><code class="language-shell">root@debian:~# mkswap /dev/vg-system/lv-swap
Setting up swapspace version 1, size = 1024 MiB (1073737728 bytes)
no label, UUID=4d315a61-ccb8-45aa-9647-f99399ac24ec</code></pre>
<p>We have now to recreate the <em>filesystem structure</em> on the new logical volume lv-root and copy all the data on it :</p>
<pre><code class="language-shell">mkdir /mnt/newroot
mount /dev/vg-system/lv-root /mnt/newroot</code></pre>
<pre><code class="language-shell">rsync -avxHAX --progress --exclude=/mnt --exclude=/proc --exclude=/sys --exclude=/dev --exclude=/run --exclude=/tmp / /mnt/newroot/</code></pre>
<p>You should see something like this at the end and no errors :</p>
<pre><code class="language-shell">sent 2,529,433,716 bytes received 1,376,360 bytes 53,280,212.13 bytes/sec
total size is 2,535,865,018 speedup is 1.00</code></pre>
<p>It is time now to mount the new root filesystem (devices, processes, sysfs, and runtime environment) :</p>
<pre><code class="language-shell">mkdir -p /mnt/newroot/{dev,proc,sys,run,tmp}
mount --bind /dev /mnt/newroot/dev
mount --bind /proc /mnt/newroot/proc
mount --bind /sys /mnt/newroot/sys
mount --bind /run /mnt/newroot/run</code></pre>
<p>Now that the new root filesystem is ready and all the special filesystems are mounted, we can chroot into it and finalize the setup:</p>
<pre><code class="language-shell">root@debian:~# chroot /mnt/newroot
root@debian:/#</code></pre>
<p>Inside the chroot, we will now create the fstab file so that the system knows how to mount the new volumes at boot. </p>
<p><u>Tip </u><em> I’m using the EOF block so that everything between the first </em>&lt;&lt; 'EOF'<em> and the </em>final EOF<em> gets written into the /etc/fstab file.</em>
<br>It’s simply a way to insert a block of text into a file directly from the shell without using a text-editor like <em>nano</em>,<em>n.vi.m</em> or even <em>echo</em>.</p>
<pre><code class="language-shell">cat &gt; /etc/fstab &lt;&lt; 'EOF'
# LVM Configuration
/dev/vg-system/lv-root / ext4 defaults 0 1
/dev/vg-system/lv-swap none swap sw 0 0
# Temporary filesystems
tmpfs /tmp tmpfs defaults,nodev,nosuid,noexec 0 0
EOF</code></pre>
<p>We now need to regenerate the <strong>initramfs</strong>, an early-boot filesystem that includes all the drivers and tools the kernel needs to find and mount the root filesystem :</p>
<pre><code class="language-shell">root@debian:/# update-initramfs -u -k all
update-initramfs: Generating /boot/initrd.img-6.1.0-39-amd64
update-initramfs: Generating /boot/initrd.img-6.1.0-25-amd64</code></pre>
<p>Next, we need to install the <strong>bootloader</strong> GRUB, so our system knows how to boot.</p>
<pre><code class="language-shell">root@debian:/# grub-install /dev/sdb
Installing for i386-pc platform.
Installation finished. No error reported.</code></pre>
<p>After that, we regenerate GRUB’s configuration :</p>
<pre><code class="language-shell">root@debian:/# update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-6.1.0-39-amd64
Found initrd image: /boot/initrd.img-6.1.0-39-amd64
Found linux image: /boot/vmlinuz-6.1.0-25-amd64
Found initrd image: /boot/initrd.img-6.1.0-25-amd64
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
done</code></pre>
<p>We can exit the chroot, dismount the <em>/dev</em>, <em>/proc</em>, <em>/sys</em> and <em>/run</em> that we previously mounter, shut the vm down and disable the old disk, select the new disk in the boot order and simply boot the virtual machine up.</p>
<pre><code class="language-shell">umount /mnt/newroot/dev
umount /mnt/newroot/proc
umount /mnt/newroot/sys
umount /mnt/newroot/run
umount /mnt/newroot</code></pre>
<p>In the boot order of you virtual machine, you should only see the network card and the new disk you've juste migrated to.
<img src="../img/bootorder.png" alt="Image description" /></p>
<p>We are now booting on the new disk with LVM !
<img src="../img/boot.png" alt="Image description" /></p>
<h2>Verification and testing</h2>
<p>First thing first, let's check our disks with <code>fdisk -l</code> and a <code>df -h</code>: </p>
<pre><code class="language-shell">root@debian:~# fdisk -l
Disk /dev/sda: 5 GiB, 5368709120 bytes, 10485760 sectors
Disk model: QEMU HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x931446ee
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 10485759 10483712 5G 8e Linux LVM
Disk /dev/mapper/vg--system-lv--swap: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/vg--system-lv--root: 4 GiB, 4290772992 bytes, 8380416 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes</code></pre>
<pre><code class="language-shell">root@debian:~# df -h
Filesystem Size Used Avail Use% Mounted on
udev 963M 0 963M 0% /dev
tmpfs 197M 584K 197M 1% /run
/dev/mapper/vg--system-lv--root 3.9G 2.6G 1.1G 71% /
tmpfs 984M 0 984M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 984M 0 984M 0% /tmp
overlay 3.9G 2.6G 1.1G 71% /var/lib/docker/overlay2/ab90d480e6ec488256582f1bd9cff1a19bf69d1d2bf5f7c4bf7b66c4f5de9764/merged
tmpfs 197M 0 197M 0% /run/user/1000</code></pre>
<p>Then let's check our LVM configuration with LVM with <code>pvs</code>, <code>vgs</code> and <code>lvs</code> :</p>
<pre><code class="language-shell">root@debian:~# pvs
PV VG Fmt Attr PSize PFree
/dev/sda1 vg-system lvm2 a-- &lt;5.00g 0</code></pre>
<pre><code class="language-shell">root@debian:~# vgs
VG #PV #LV #SN Attr VSize VFree
vg-system 1 2 0 wz--n- &lt;5.00g 0</code></pre>
<pre><code class="language-shell">root@debian:~# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
lv-root vg-system -wi-ao---- &lt;4.00g
lv-swap vg-system -wi-ao---- 1.00g</code></pre>
<p>Our final test will be to see if our docker is still runnig and working with <code>docker ps</code> and <code>curl</code> :</p>
<pre><code class="language-shell">root@debian:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a5fec5ba4df5 louislam/uptime-kuma:1 "/usr/bin/dumb-init …" 4 hours ago Up 5 minutes (healthy) 0.0.0.0:3001-&gt;3001/tcp, :::3001-&gt;3001/tcp uptime-kuma</code></pre>
<pre><code class="language-shell">root@debian:~# curl localhost:3001
Found. Redirecting to /dashboardroot@debian:~#</code></pre>
<h2>Expanding your VM disk space</h2>
<p>So <strong>all of this</strong> was to one day, if needed, I could expand my VM disk storage.
In Proxmox, <em>Hardware</em> &gt; click on the Hard Drive you want to expand &gt; <em>Disk Actions</em> &gt; <em>Resize</em>.
Let's say I added 5 more Gigs, because the current 5G I gave the VM are not enough, we now have 10G disk storage, but only 5G are used by the filesystem.</p>
<pre><code class="language-shell">root@debian:~# fdisk -l
Disk /dev/sda: 10 GiB, 10737418240 bytes, 20971520 sectors
Disk model: QEMU HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x931446ee
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 10485759 10483712 5G 8e Linux LVM
Disk /dev/mapper/vg--system-lv--swap: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/vg--system-lv--root: 4 GiB, 4290772992 bytes, 8380416 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes</code></pre>
<p>We can see that we have a single partition, <em>/dev/sda1</em>. We'll use <code>parted</code> to manage disk partitions :</p>
<pre><code class="language-shell">root@debian:~# parted /dev/sda
GNU Parted 3.5
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print
Model: QEMU QEMU HARDDISK (scsi)
Disk /dev/sda: 10.7GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 5369MB 5368MB primary boot, lvm
(parted) resizepart 1 100%</code></pre>
<p>We can verify that the entire 10GB is now allocated to /dev/sda1:</p>
<pre><code class="language-shell">(parted) print
Model: QEMU QEMU HARDDISK (scsi)
Disk /dev/sda: 10.7GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 10.7GB 10.7GB primary boot, lvm</code></pre>
<p>Next, we resize our LVM <em>Physical Volume</em> with <code>pveresize</code> and check that the newly available space (5GB) is recognized:</p>
<pre><code class="language-shell">root@debian:~# pvresize /dev/sda1
Physical volume "/dev/sda1" changed
1 physical volume(s) resized or updated / 0 physical volume(s) not resized</code></pre>
<p>Then we verify that the Volume Group sees the free space with <code>vgs</code>:</p>
<pre><code class="language-shell">root@debian:~# vgs
VG #PV #LV #SN Attr VSize VFree
vg-system 1 2 0 wz--n- &lt;10.00g 5.00g</code></pre>
<p>We extend the Logical Volume using <code>lvextend</code>:</p>
<pre><code class="language-shell">root@debian:~# lvextend -l +100%FREE /dev/vg-system/lv-root
Size of logical volume vg-system/lv-root changed from &lt;4.00 GiB (1023 extents) to &lt;9.00 GiB (2303 extents).
Logical volume vg-system/lv-root successfully resized.</code></pre>
<p>Finally, we resize the filesystem to use the new space with <code>resize2fs</code> :</p>
<pre><code class="language-shell">root@debian:~# resize2fs /dev/vg-system/lv-root
resize2fs 1.47.0 (5-Feb-2023)
Filesystem at /dev/vg-system/lv-root is mounted on /; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/vg-system/lv-root is now 2358272 (4k) blocks long.</code></pre>
<p>We can check with <code>df -h</code> that the root filesystem now has more available space:</p>
<pre><code class="language-shell">root@debian:~# df -h | grep root
/dev/mapper/vg--system-lv--root 8.8G 2.6G 5.8G 31% /</code></pre>
<h2>Renaming</h2>
<p>Let's take a look at my brand new debian12-template that has LVM :</p>
<pre><code class="language-shell">root@deb12-template:~# df -h | grep root
/dev/mapper/deb12--template--vg-root 15G 1.7G 12G 13% /</code></pre>
<p>If you ever clone it and rename the host (with <code>hostnamectl sethostname</code> and editing <em>/etc/hosts</em> ), you'll be stuck with the same VG name. And you may want to rename it. Here's are a few steps to achieve that :</p>
<ul>
<li>using <code>vgrename</code> to rename the VG (make sense)</li>
<li>updating <em>/etc/fstab</em> with the new VG name</li>
<li>updating <em>/etc/initramfs-tools/conf.d/resume</em> (if you have swap)</li>
<li>regenerating the <em>initramfs</em> </li>
<li>updating <em>grub</em></li>
</ul>
<p>Step one : <u> using vgrename to rename the VG (make sense) </u></p>
<p>Here I decided to rename it system-vg but you can rename it whatever suits you.</p>
<pre><code class="language-shell">root@deb12-template:~# vgs
VG #PV #LV #SN Attr VSize VFree
deb12-template-vg 1 2 0 wz--n- &lt;15.52g 0
root@deb12-template:~# vgrename deb12-template-vg system-vg
Volume group "deb12-template-vg" successfully renamed to "system-vg"
root@deb12-template:~# vgs
VG #PV #LV #SN Attr VSize VFree
system-vg 1 2 0 wz--n- &lt;15.52g 0</code></pre>
<p>Step two : <u> updating <em>/etc/fstab/</em> with the new VG name </u></p>
<p>My current <em>/etc/fstab</em> is currently looking like this :</p>
<pre><code class="language-shell">root@deb12-template:~# cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# systemd generates mount units based on this file, see systemd.mount(5).
# Please run 'systemctl daemon-reload' after making changes here.
#
# &lt;file system&gt; &lt;mount point&gt; &lt;type&gt; &lt;options&gt; &lt;dump&gt; &lt;pass&gt;
/dev/mapper/deb12--template--vg-root / ext4 errors=remount-ro 0 1
# /boot was on /dev/sda1 during installation
UUID=f4ca6e38-0263-4fe1-95f1-dc0cf9449ce2 /boot ext2 defaults 0 2
/dev/mapper/deb12--template--vg-swap_1 none swap sw 0 0
/dev/sr0 /media/cdrom0 udf,iso9660 user,noauto 0 0</code></pre>
<p>You want to replace the <em>deb12-template</em> with <em>system</em>. Using vi(m), it is simple with <code>:%s/oldtexttoreplace/replacement/g</code>, which would be <code>:%s/deb12--template/system/g</code>. So now, my <em>/etc/fstab</em> is now looking like this :</p>
<pre><code class="language-shell">root@deb12-template:~# cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# systemd generates mount units based on this file, see systemd.mount(5).
# Please run 'systemctl daemon-reload' after making changes here.
#
# &lt;file system&gt; &lt;mount point&gt; &lt;type&gt; &lt;options&gt; &lt;dump&gt; &lt;pass&gt;
/dev/mapper/system--vg-root / ext4 errors=remount-ro 0 1
# /boot was on /dev/sda1 during installation
UUID=f4ca6e38-0263-4fe1-95f1-dc0cf9449ce2 /boot ext2 defaults 0 2
/dev/mapper/system--vg-swap_1 none swap sw 0 0
/dev/sr0 /media/cdrom0 udf,iso9660 user,noauto 0 0</code></pre>
<p>Step three (optionnal, only if you have swap) : <u> updating /etc/initramfs-tools/conf.d/resume </u></p>
<pre><code class="language-shell">root@deb12-template:~# cat /etc/initramfs-tools/conf.d/resume
RESUME=/dev/mapper/deb12--template--vg-swap_1</code></pre>
<p>Once again, we replace the <em>deb12--template</em> with <em>system</em>.</p>
<pre><code class="language-shell">root@deb12-template:~# cat /etc/initramfs-tools/conf.d/resume
RESUME=/dev/mapper/system--vg-swap_1</code></pre>
<p>Step four : <u> regenerating the initramfs </u></p>
<p>This part should be the easiest one if everything else before runned smoothly. We will regenerating the initramfs with <em>update-initramfs -u -k all</em> :</p>
<pre><code class="language-shell">root@deb12-template:~# update-initramfs -u -k all
update-initramfs: Generating /boot/initrd.img-6.1.0-39-amd64
update-initramfs: Generating /boot/initrd.img-6.1.0-25-amd64</code></pre>
<p>Last step : <u> updating grub </u></p>
<p>We now have to update the <em>/boot/grub/grub.cfg</em> which still has the deb12--template VG name.</p>
<pre><code class="language-shell">root@deb12-template:~# cat /boot/grub/grub.cfg | grep deb12--template
linux /vmlinuz-6.1.0-39-amd64 root=/dev/mapper/deb12--template--vg-root ro quiet
linux /vmlinuz-6.1.0-39-amd64 root=/dev/mapper/deb12--template--vg-root ro quiet
linux /vmlinuz-6.1.0-39-amd64 root=/dev/mapper/deb12--template--vg-root ro single
linux /vmlinuz-6.1.0-25-amd64 root=/dev/mapper/deb12--template--vg-root ro quiet
linux /vmlinuz-6.1.0-25-amd64 root=/dev/mapper/deb12--template--vg-root ro single</code></pre>
<p>Again, we'll use n.vi.m and <code>:%s/x/y/g</code> to replace every occurence of <em>deb12--template</em></p>
<pre><code class="language-shell">root@deb12-template:~# cat /boot/grub/grub.cfg | grep system
linux /vmlinuz-6.1.0-39-amd64 root=/dev/mapper/system--vg-root ro quiet
linux /vmlinuz-6.1.0-39-amd64 root=/dev/mapper/system--vg-root ro quiet
linux /vmlinuz-6.1.0-39-amd64 root=/dev/mapper/system--vg-root ro single
linux /vmlinuz-6.1.0-25-amd64 root=/dev/mapper/system--vg-root ro quiet
linux /vmlinuz-6.1.0-25-amd64 root=/dev/mapper/system--vg-root ro single</code></pre>
<p>Then simply reboot, and it should be good !</p>
<pre><code class="language-shell">root@deb12-template:~# df -h | grep root
/dev/mapper/system--vg-root 15G 1.7G 12G 13% /</code></pre>
<p>Thanks for reading me,
<br>spleenftw</p>
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