LVM

2016-11-05
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Storage + Data >

This concept and these notes are entirely obsoleted by dm-crypt, if you want a complete encryption solution.

These notes were made from instructions from Slackware as of Slackware 14.2 64bit.

It's remarkably simple.

  • Logical Volume Management

Thanks to http://ftp.slackware.com/pub/slackware/slackware-current/README_LVM.TXT

Table of Contents [hide]

Partitioning ∞

fdisk or cfdisk are available on Slackware's install media.

  • Create a large partition which will become your LVM Volume Group. Perhaps you will use one big partition that takes up a whole disk.

    • See Partition Alignment for the advanced user, although as of this writing (2016-11-04) things seem to either be automatic or "good enough" for an everyday user.
    • Set this partition's type to 8e (Linux LVM).

LVM setup ∞

Here is a suggested layout:

physical_volume=/dev/sdx1
volume_group=myvg

pvcreate                 $physical_volume
vgcreate  $volume_group  $physical_volume
lvcreate  -L 15G       -n root  $volume_group
lvcreate  -L 4G        -n home  $volume_group
lvcreate  -L 4G        -n swap  $volume_group
lvcreate  -L 100%FREE  -n data  $volume_group
mkswap /dev/$volume_group/swap

More advanced users might make targets for /usr, /etc and perhaps /var.

a note on the size of your swap partition

The size of the swap partition is debatable, but the (double your RAM size) is false.

  • 4GB of RAM and under would be fine with 2GB of swap.

  • Over 4GB would be fine with 4GB of swap.

A swap is only relevant if you use a lot of your memory, and most Linux computers don't even come close. It's still a good idea to have it, just in case.

Hibernation (suspend to disk) may have specific requirements, but I don't know enough to advise.

I've read that a swap file (not partition) is not supported on Btrfs but I haven't confirmed that.

Slackware's setup ∞

  • Run Slackware's setup

  • Select your various LVM targets

    • root for /
    • home for /home
    • swap for your swap
    • data mounted perhaps at /data

  • Proceed with configuring your LILO as usual, and select /dev/myvg/root as your root filesystem to boot.

    • If LILO generates warnings or errors, ignore them in this step.

  • Complete your use of Slackware's setup, but do not reboot yet!

mkinitrd ∞

  • First enter a chroot:

chroot  /mnt

  • The next step can be done the easy way with:

/usr/share/mkinitrd/mkinitrd_command_generator.sh -r

.. if it looks good, you can execute it like:

$( /usr/share/mkinitrd/mkinitrd_command_generator.sh -r )
details 

# mkinitrd -c -k 4.4.14-smp -m ext4 -f ext4 -r /dev/myvg/root -L

filesystem=ext4       # Or perhaps you use btrfs
kernel='4.4.14-smp'   # The default Slackware 14.2 SMP kernel
volume_group=myvg

mkinitrd  -c  -k $kernel  -m $filesystem  -f $filesystem  -r /dev/$volume_group/root  -L

for a non-US keyboard

If you use a non-US keyboard, don't forget to include your language code.

An example with the Dutch (nl) keyboard is:

mkinitrd  -c  -k $kernel  -m $filesystem  -f $filesystem  -r /dev/myvg/root  -L  -l nl

Configure LILO ∞

(LILO)

  • Edit /etc/lilo.conf

    • Nano is not available. You'll have to use vi. Ugh.

  • Look for "Linux bootable partition config"

    • Add a line for the initrd.
    • Change the filename of the kernel to be used. We will need to use a generic kernel.
why use a generic kernel?

We also need to change the kernel file to a generic kernel, because lilo is unable to combine the 'huge' kernels in Slackware 14.2 with an initrd image - it will complain about "The initial RAM disk is too big to fit between the kernel and the 15M-16M memory hole" if you try a 'huge' kernel. We can live with that, since the 'huge' kernels are not meant for day-to-day use anyway. They are meant to install Slackware on a wide range of computers and that is why they are 'huge'.

It should look somewhat like this:

  image = /boot/vmlinuz-generic-smp-4.4.14-smp
    initrd = /boot/initrd.gz
    root = /dev/myvg/root
    label = linux
    read-only
  • When satisfied, save the changes to this file.

  • Run lilo while still in the chroot.

    • Lilo will issue a couple of warnings concerning a difference in what /proc/partitions reports and what lilo thinks are available partitions, but it is safe to ignore these.

  • Exit the chroot:

exit

  • Reboot

You are done!

RAID with LVM ∞

(RAID)

(No notes have been taken.)

Notes ∞

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