Change partition or logical volume (LV) order in LVM

Preface

After creating logical volumes in LVM I noticed I had created them in the wrong order. If it makes a difference or not is another question, but I wanted my root volume to appear before my swap volume.

This can be done by chaning the minor decice number of the logical volume. Lower numbers comes before higher ones, hence, I want to make root a lower number than swap.

Changing minor device numbers of logical volumes in LVM

The manpage (man lvchange) describes the options well enough with the description

Make the minor device number persistent for an LV. […]

Let’s take a look at the layout of my volume group (VG), Main:

$ lsblk /dev/nvme0n1p3
NAME          MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
nvme0n1p3     259:3    0 475.4G  0 part
└─lvm         254:0    0 475.4G  0 crypt
  ├─Main-swap 254:1    0    16G  0 lvm   [SWAP]
  ├─Main-root 254:2    0   100G  0 lvm   /
  └─Main-home 254:3    0   310G  0 lvm   /home

Here we can see that the major device number for the VG is 254, while the minor numbers increment by one for each of the LV’s.

I want Main-root to have number 1, and swap to be number 2. To do that, I first have to move Main-swap to a free number, e.g. 7. If any of the volumes are currently active, you will be asked if it’s okay to deactivate them temporarily.

# lvchange --persistent y --minor 7 /dev/Main/swap

Then set Main-root to number 1 now that it should be available

# lvchange --persistent y --minor 1 /dev/Main/root

Set Main-swap again to number 2

# lvchange --persistent y --minor 2 /dev/Main/swap

Now, since the volumes were deactivated, activate them all again

# lvchange --activate ay /dev/Main

ay here means the following:

ay specifies autoactivation, in which case an LV is activated only if it matches an item in lvm.conf activation/auto_activation_volume_list. If the list is not set, all LVs are considered to match, and if if the list is set but empty, no LVs match

If this doesn’t activate your volumes, you may want y instead.

References

• man lvchange