Gentoo LVM2 installationThis guide is based on an example with two SATA hard disks. It means that you will more than likely need to change the drive, partition names and partition sizes to match your own setup and needs.
If you do a fresh install of Gentoo, you will need to use a bootable CD with LVM2 support such as a Gentoo Installation CD. You can find the Installation CDs for an x86 architecture on our mirrors under /releases/x86/current/installcd. Other architectures might be supported as well. If you install LVM2 on a currently running system with some spare hard disk space, you will need to enable the LVM2 module (dm-mod) in the kernel. This module is available in gentoo-sources. Compiling your kernel and getting LVM2 to work is covered later in this guide. Our example system has two SATA hard disks and will be partitioned as follows:
OK, time to start... Follow the handbook, but with the following amendments to chapter 4. Preparing the Disks: Use fdisk as described in the handbook, but use the partition scheme mentioned above as an example. It is only an example, adapt it to your own needs. Create a small physical /boot partition (sda1). In this example, /boot will be not managed by LVM2. This partition will contain your bootloader and your kernel(s). A 64MB partition should be well enough for quite a few kernel generations. Create a swap partition (sda2). Create a / (root) partition (sda3). If you are interested in trying to put your root partition under LVM management (which we do not recommend), see the resources section at the end of this guide for a link to a mini-howto on how to do this. The size of the root partition need not be large if you will keep /opt /usr /home /var and /tmp in an LVM2 Volume Group (vg). In this case, 1GB should be sufficient. Note however that, if you have /usr or /var in an LVM2 volume group, you will need to boot the system with an initramfs.
Assuming the /boot, swap and root partitions do not use the whole physical disk, create a fourth partition on this disk and set it to type 8e (Linux LVM). If you have more physical drives you would like to use with LVM, create one partition on each and give them the same type (8e).
Create the filesystems on /dev/sda1 and /dev/sda3, and create and activate the swap on /dev/sda2 as described in the handbook. Start the lvm service.
It is recommended to add the lvm service to the boot runlevel. This way LVM2 will be activated each time the system boots.
Before scanning and activating LVM, you might want to edit /etc/lvm/lvm.conf to exclude some devices. By default, LVM2 will scan all devices, even your CDROM which can generate error messages. In the following example, the line that allows scanning of all devices is replaced by one that rejects every device but our two SATA disks.
Prepare the partitions.
Setup a volume group. A volume group is the result of combining several physical units into a single logical device. In our example, /dev/sda1, /dev/sda2 and /dev/sda3 are the /boot, swap and root partitions so we need to combine /dev/sda4 and /dev/sdb1. It can be done with a single command, but, as an example, we will create our volume group and extend it.
Create the logical volumes. Logical volumes are the equivalent of partitions you would create using fdisk in a non LVM2 environment. In our example, we create the following partitions:
Since we are going to use LVM2, we should not worry too much about partition sizes because they can always be expanded as needed.
Create filesystems on the logical volumes the same way you would on a regular partition. We use ext3 on the logical volumes but any filesystem of your choice will work:
Mount your partitions as described in the handbook and mount your LVM2 logical volumes as if they were partitions. Replace the usual /dev/sdxx with /dev/vg/logical_volumename.
When configuring your kernel, make sure to configure your kernel to support LVM2. Select the LVM2 module as follows:
The compiled module is called dm-mod.ko Also build an initramfs if you have /usr or /var on an LVM-based partition. Don't forget to edit your boot loader to boot the system with the initramfs and add in dolvm as a boot parameter.
Now, install the lvm2 package.
Edit /etc/lvm/lvm.conf as described earlier. The file you previously edited is part of your installation environment and will disappear after the next reboot. This time, you edit the real one inside your new Gentoo install. When editing your /etc/fstab file, follow the handbook and add your LVM2 logical volumes as needed. Again, here are a few lines needed for our example:
When you reach the end of the installation part of the handbook, don't forget to umount all your LVM2 logical volumes as well and for a good measure run the following command before you reboot:
Restart your machine and all partitions should be visible and mounted. If you have interrupted the Gentoo installation at one point and want to continue, you need to create the volume device nodes first:
Installation CDs with less recent tools might need to reactivate the volumes instead:
Thanks Thilo Bangert and Terje Kvernes for their help and comments on this document. The contents of this document, unless otherwise expressly stated, are licensed under the CC-BY-SA-2.5 license. The Gentoo Name and Logo Usage Guidelines apply. |
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