Quick Gentoo LVM howto

I hope to expand this eventually but for now just how to mount an LVM partition already created by Gentoo or another Linux distro.

# mount /dev/sda5 /mnt/gentoo
mount: unknown filesystem type 'LVM2_member'

That does not work so...

# pvs
livecd ~ # pvs
  PV         VG         Fmt  Attr PSize   PFree
  /dev/sda5  bcid       lvm2 a--  465.52g    0

This shows you the detected LVM partitions on your machine, now we will have a look inide them. Dont worry if you don't have a /dev/bcid directory, this utility does not actually look at that anyway.

# lvdisplay /dev/bcid
  --- Logical volume ---
  LV Path                /dev/bcid/root
  LV Name                root
  VG Name                bcid
  LV UUID                jTF0xU-vLIj-lTsh-9qdW-fMEh-AI1o-oL0UjF
  LV Write Access        read/write
  LV Creation host, time ,
  LV Status              available
  # open                 0
  LV Size                461.68 GiB
  Current LE             118190
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

  --- Logical volume ---
  LV Path                /dev/bcid/swap_1
  LV Name                swap_1
  VG Name                bcid
  LV UUID                i7dAhY-bZw2-hcKe-dXcL-Yzgk-O8Xn-Z8Tdx5
  LV Write Access        read/write
  LV Creation host, time ,
  LV Status              available
  # open                 0
  LV Size                3.84 GiB
  Current LE             983
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1

Now you can see the partitions embedded inside this LVM2 partition. Next we need to see if it is active, with the Gentoo minimal CD it probably won't be.

# vgchange /dev/bcid -a y
  2 logical volume(s) in volume group "bcid" now active

You will now find that your /dev directory has some new files! In this case we have created /dev/bcid, /dev/bcid/root and /dev/bcid/swap_1.

I am not sure how to "deactivate" them and this was a repair on a client machine so I did not have the time to go experimenting but this should be enough for you to be getting on with. One last thing:

# lvscan
  ACTIVE            '/dev/bcid/root' [461.68 GiB] inherit
  ACTIVE            '/dev/bcid/swap_1' [3.84 GiB] inherit

Good luck with your LVMin'