How to setup LVM (Logical Volume Manager) including root und

[arkane]

How to setup LVM (Logical Volume Manager) including root under Gentoo

ChangeLog: 05/20/2002 - Added in need to compile devfs mounted at boot for the kernel and the fact that you can use resize2fs to resize ext3 partitions.

Preface
This document describes how I setup LVM on Gentoo, along with any tiny items you should know along the way.
I used Gentoo 1.1a for this example. This is meant to compliment the Gentoo installation instructions.
This is best done during system installation, as then you don't have to swap around contents of a drive.
However, feel free to explore on your own and try new things!

1. Before going too far, you need to first plot out how your going to setup your partitions. (any partitions
you setup in LVM can be resized) Mine are as follows:

Code:

Filesystem      Type      Size  Used Avail Use% Mounted on /dev/hda6       ext3       23M  4.2M   17M  20% /boot /dev/nostripevg/rootlv ext3      147M  112M   28M  80% / /dev/nostripevg/usrlv ext3      1.7G  978M  677M  60% /usr /dev/nostripevg/varlv   reiserfs  252M   40M  212M  16% /var /dev/nostripevg/homelv  reiserfs 1000M   40M  960M   4% /home /dev/nostripevg/x11lv   ext3      170M  112M   50M  69% /usr/X11R6 tmpfs          tmpfs     1.0M  112K  912K  11% /mnt/.init.d

Keep your partitioning as a reference during the installation.

2. Go through the instructions until section 6 (Set Up Partitions). This section needs a little clarifying.
You need 2 partitions (aside from the one(s) for LVM), one for your /boot partition and one for swap.
So, for this example, we're going to create the following partitions: swap, LVM, boot.

Inside fdisk:

• Create the partition for /boot to be between 20-50MB as you would any other partition.
  (It only holds your initrd, kernel, and grub items)
  
• Change the "type" to 83 (Linux) with the "t" command.
  
• Create your LVM partition partition to be the size of your full system. (Mine is 5.6 Gigabytes)
  
• Change the "type" to 8e (Linux LVM) with the "t" command
  
• Create your swap partition. (Size is at your discretion. Standards are >=2*RAM, but I use 136mb)
  
• Change the "type" to 82 (Linux swap) with the "t" command
  

After You've done that, if you type "p" in fdisk it should resemble my setup (seen below):

Code:

Disk /dev/hda: 255 heads, 63 sectors, 1247 cylinders Units = cylinders of 16065 * 512 bytes    Device Boot    Start       End    Blocks   Id  System /dev/hda6  *        523       525     24066   83  Linux /dev/hda7           526      1230   5662881   8e  Linux LVM /dev/hda8          1231      1247    136521   82  Linux swap

After your sure everything is fine, use the "w" command to write the changes to disk.

3. Time to setup LVM!

• Type: vgscan
  
• Create your physical volume for the LVM partition we made. Type: pvcreate /dev/hd?? (change ?? to your partition)
  
• Create your volume group for LVM. The volume group is whats used to allocate your logical volumes in LVM.
  If your not using devfs
  Type:

  Code:

  vgcreate my_volume_group /dev/hda1

  
  (replace hda1 with the partition made for LVM, and my_volume_group with a name for your Logical Volume)
  If you ARE using devfs
  Type:

  Code:

  vgcreate my_volume_group /dev/ide/host0/bus0/target0/lun0/part1

  
  (you have to use the full devfs name for the drive/partition. Above is equal to /dev/hda1)
  
• Create your logical volumes. (basically, "partitions" as you originally thought of them, only created in LVM)
  Type: lvcreate -LsizeMB -ntestlv testvg
  Replace sizeMB with how many megabytes you want the partition to be, testlv with the name of your partition,
  and testvg with the name of the volume group you gave in the last step.
  You can name your logical volumes anything easy to remember, as I use rootlv, usrlv, homelv, etc...
  You need to do this for all of the partitions you planned out in the beginning.
  
• After that, time to create filesystems on the partitions we've created.
  Please note that out of all the filesystems, XFS is *NOT* able to shrink at all. It can only grow. Also note that as of this date, resize_reiserfs is not included in the boot cd so be careful when you allocate space for reiserfs. You can resize ext3 partitions with the tool resize2fs.
  
  
  
  1. Do the /boot partition. You have a choice of filesystems, so use the one your most comfortable with.
     Follow section 6 of the installation instructions for examples.
     
  2. Do the swap. (mkswap /dev/hda8 for example)
     
  3. Now, on to the LVM partitions. Instead of being /dev/hda1, /dev/hda2, and so on, LVM has a different setup
     LVM names it's partitions in the following way: /dev/volumegroup/logicalvolume (e.g. /dev/test_vg/rootlv)
     So, suppose my volume group was "testvg" and I created a logical volume inside of it called "linuxlv".
     It would be called, "/dev/testvg/linuxlv". You can format it as you do any other device.
     

     Code:

     e.g. mke2fs /dev/testvg/linuxlv

     
     

4. Mounting LVM Partitions
It's quite simple, and the same as you would any other drive.
To mount our linuxlv partition to the root, we do the following:

Code:

mount /dev/testvg/linuxlv /

Make sure when you follow section 7 of the install instructions to mount ALL of your LVM partitions.
Also, be sure to include the partition we created for /boot

5. Onto step 14, you will notice that the Gentoo linux-sources has changed a bit from the instructions.
I personally used sys-kernel/gentoo-sources because I am not using XFS but it does include LVM.
You can grab any of them except for the vanilla-sources. Be sure to include built-in support for LVM
when compiling the kernel.
Options needed when running make menuconfig:

• LVM support
  
• built-in ramdisk support with initrd
  
• DEVfs support
  
• mount dev filesystem at boot
  
• loopback support
  

I have noticed issues with grsecurity in the kernel and LVM, but that's my own personal experience.
When you are finished compiling your kernel, modules, and installing both, perform the command:

Code:

lvmcreate_initrd 2.4.19-gentoo-r1

replacing 2.4.19-gentoo-r1 with the version of kernel you installed.
You will notice module errors, this is normal. (your not running the kernel yet!)
Notice the size of the loopback file. It will say:

Code:

lvmcreate_initrd -- making loopback file (3238 kB)

except your size will be different. Please make sure that the size of your ramdisk is larger than this.

6. Onto step 16, perform the steps as the instructions tell you, but be sure to use the full LVM name of the partition.
(e.g. /dev/testvg/linuxlv as our previous example could be mounted to / )
Also be sure to include /boot. This is necessary for your system to operate.

7. When you are creating your /boot/grub/menu.lst, include a line under your "kernel" line saying the following:

Code:

initrd=/boot/2.4.19-gentoo-r1.gz

Be sure to change the name of the initrd file listed above if that is not the name. Never hurts to verify!

Follow the installation instructions, and after you reboot you should be able to have everything working if you followed
the instructions.

If you want a more thorough (and non-gentoo specific) howto, please see the great Howto created by the makers of LVM at
Sistina.com Howto at http://www.sistina.com/lvm_howtos/lvm_howto

I am a relatively new user of LVM, but I wanted everyone to at least have something Gentoo specific to read before diving
in like I did. I hope this helps out! I'd also like to update this occasionally, so if anyone finds any errors please let
me know on the Gentoo message board (my username is "arkane" or my email address at dan_lund@hotmail.com)

[Praxxus]

I may very well be overlooking something, but I haven't seen this specifically mentioned yet.

In addition to the built-in support (devfs/mounted at boot, LVM, initrd) you've mentioned, it seems I had to buid loopback device support (block devices) directly into the kernel before I could get LVM working.
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[uxbod]

Coming from a HP-UX SA background and do not see the point of running LVM at home. I have just build some new servers @ work using RedHat AS and the only partitions that are LVM are /oracle & /data. All system partitions are ext3. My rationale behind this is that they will be (i hope) the only two partions that shall ever need expanding. LVM is great for that.

[474]

Thanks, I hadn't worked out how to get a root partition onto LVM so that's quite useful (although I don't envisage a root partition needing snapshots or resizing).

[arkane]

[arkane]

[jeremy_]

well, after spending about 4 hours trying to get a laptop to boot with a fresh instal of gentoo 1.4 and to use lvm, I figured I'd post the fix here. Hope it's the right place.

I tried pretty much everything, and yet I could never get grub to see my lvm partitions.

I read a post elsewhere that evms will automatically setup your lvm partitions for you and make them active upon boot. I compiled evms statically into my kernel (NOT as a module) and booted, and voila, all of my lvm partitions were located at /dev/evms/lvm/volume_group/logical_vol

All that was left was to tell grub that my root was located at root=/dev/evms/lvm/Volume00/rootfs and to adjust my fstab to also point to the evms locations.

Boom! four hours of work.... 5 lines of text editted, and I'm gentoo-lvm-luvin!
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[asimon]

To make LVM (without EVMS) work with root on a LVM volume you just have to use a adequate initrd (which can be made with lvmcreate_initrd). I think this is mentioned in this thread and described in the LVM howto. initrd is a ram disk which gets mounted as root after the kernel is loaded. Then things like lvm detection/activation can be done and afterwards the kernel mounts the actual rootfs.

EVMS is more comfortable in this regard because with EVMS the kernel itself (which means the EVMS stuff which gets compiled into the kernel) detects and activates LVM volumes at boot time. Then there is no need to have an initrd.

But note that EVMS 2, which was released a couple of days ago, has no longer boot-time volume activation. You have to use the initrd mechanism with EVMS2 too. This is because of architectural changes in the Linux kernel. With the upcoming kernel all detections and activations like LVM, EVMS, etc. will be done in user space, which means that these things are no longer done by the kernel. A initrd-like mechanism is then madatory (AFAIK initrd will be replaced in Linux 2.6 too, but I have no further information on that.)

[jeremy_]

I had tried initrd, but to no avail.

Hmmm... guess I'll start figuring it again once I have to upgrade my kernel past 2.4.
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[Simba]

I have root fs in lvm, and in the grub.conf I use kernel option root=/dev/localvg/rootlv . I have also initrd in /boot partition. but if I reboot
the pc, linux kernel don't try to find the rootlv at all, but it tried to boot it from
rootnfs, here is the warning:
Root-NFS: No NFS server available, giving up
VFS: Unable to mount root fs via NFS
...

how can I tell the kernel not to use rootnfs, but try to mount the root from
LVM? but If I use kernel option root=3a01 , where 3a01 is the major/minor number of rootlv device, it works perfectly, but I don't want to boot it in this way.
thanks,
cahya

[asimon]

[atac]

this was just what i was looking for, gonna try it out
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[Simba]

After I removed the "Root file system on NFS" from the kernel, the boot
process in my laptop works perfectly. With this experience I want also to setup our compaq server (with hardisk raid) to have root fs on lvm. I do the same in the kernel:
# LVM support
# built-in ramdisk support with initrd
# DEVfs support
# mount dev filesystem at boot
# loopback support

and here is my grub.conf:

[Crimson Rider]

I can complete allmost all the steps, up to and including booting with GRUB, however, at the end of the line, vgscan and vgchange come up with zilch. nothing nada. It' doesn't find my /dev/lv/ide volume group, could that have something to do with the fact that it is on a promise onboard non-raid ide controller ?

[alexbuell]

Can I use both LVM and RAID? Is it even safe?
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Linux - the best text adventure game ever.

[Xenophon]

I have successfully created the partitions suggested above (root, boot, swap, and lvm) and have created four logical volumes (tmp, usr, var, home). I have mounted everything accordingly:

[eivinn]

[JollyToad]

Hello to all you brave LVM users.

I've just spent several hours of head scratching and chin stroking trying to install
our new server with root on LVM, here's a little story for you:

I decided to use reiserfs for all filesystems, so when it came to kernel compilation
(using gs-sources) I selected ONLY reiserfs (who needs ext2 - I thought).
Anyway, after much tweaking, many reboots, lots of kernel panics, and close
scruntity of lvmcreate_initrd - i discovered it uses ext2 on the initrd!
One kernel recompile and reboot later - and hey presto - a working root on LVM.

The moral of this story is:
Don't forget to compile 'EXT2' filesystem support into the kernel

[eivinn]

[Birdman]

[Neo_0815]

hello.

I decided to use lvm and i've done all things described as in here, but got following error:

vgcreate main /dev/ide/host2/bus0/target0/lun0/part4
vgcreate -- no valid physical volumes in command line

lvm-mod is aktivated in my 2.4.22-r7 gentoo-sources kernel, devfs is also up and running.
my partition scheme looks like this:

Name Flags Part. Typ Dateisystemtyp [Bezeichner] Size
------------------------------------------------------------------------------
hde1 Primäre Linux ext3 49,36
hde2 Primäre Linux ext3 246,76
hde3 Primäre Linux swap 1998,75
hde4 Primäre Linux LVM 117761,34

/boot, /, swap and lvm volume in the above order.

I executed vgscan before and got this:

vgscan -- reading all physical volumes (this may take a while...)
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: This program does not do a VGDA backup of your volume group

Whats the problem, what i am doing wrong.

thx and best regards

Neo

[deepthink]

I intalled LVM on my new laptop. This is my current setup:

[Neo_0815]

I've took lvm2 and get following more detailed error:

vgcreate main /dev/ide/host2/bus0/target0/lun0/part4
No physical volume label read from /dev/ide/host2/bus0/target0/lun0/part4
/dev/ide/host2/bus0/target0/lun0/part4 not identified as an existing physical volume
Unable to add physical volume '/dev/ide/host2/bus0/target0/lun0/part4' to volume group 'main'.

What i am doing wrong?

best regards

[One]

this is quite easy I think.

before you can use a partition with lvm you have to initialize this partition as a physical lvm partition ...

this is done by executing pvcreate (partition-name)

I hope this solves your problem

[Neo_0815]

thx very much.
now it works.

best regards