Installing Slackware on Logical volumes ======================================= Introduction ------------ For a long time, it has been common for other distros to support installation to Logical Volumes. In Slackware, the installer has never supported this, but the gurus usually would find a way to create logical volumes and install or migrate their Slackware onto those. Having your Slackware installed fully on LVM was near impossible until Slackware 12.0, but now Slackware has improved support for LVM built into the installer. Preparing Logical Volumes (LV) ------------------------------ * Existing LV The Slackware installer will recognize and activate any pre-existing Logical Volumes on your hard drive(s). These Logical Volumes will be selectable targets for the creation of the filesystems (like /, /usr, /home, /var) * New LV When you need to create the LV, you need to do this before starting the 'setup' program. You may have to run (c)fdisk first to create the partition you want to use for setting up the logical volumes. For any partition you create and that you want to use for LVM, you should set the partition type to '8e' (Linux LVM). In the next example, I will assume we use a single 20 GB partition '/dev/sda1' for our Volume Group (VG). With LVM, it is possible to use multiple physical volumes (i.e. partitions, whole disks) for a VG, but that is left as an exercise for the reader. You can always add extra physical volumes to your VG later. We will create a VG called 'myvg' and on that VG create two LV's called 'root' and 'home'. The first is going to contain the root partition ('/') and the second will become our '/home' partition. After booting your computer from the Slackware CD/DVD/USB, and logging in as root, you run the following sequence of commands to create the Physical Volume (PV), the Volume Group (VG) within that PV and two LV's of size 15GB (root) and 4GB (home) inside the VG: # pvcreate /dev/sda1 # vgcreate myvg /dev/sda1 # lvcreate -L 15G -n root myvg # lvcreate -L 4G -n home myvg ======================================================================== NOTE: if you want, you can just allocate all remaining space inside the VG to a Logical Volume. Suppose we want to allocate all available space to our 'home' LV, then this will the command to use instead of the previous one (note the use of '-l' instead of '-L'): # lvcreate -l 100%FREE -n home myvg ======================================================================== The device nodes for the logical volumes are created, and the volumes will be activated automatically when running lvcreate. This is all we need to do before running 'setup'. Using LVM during setup ---------------------- In setup, when you choose "TARGET" in the main menu, you will notice that the LV's are available in the Linux partition selection. Our two LV's "root" and "home" are visible as "/dev/myvg/root" and "/dev/myvg/home". Select the first for your root ('/') filesystem, and the other for your /home filesystem. Create any filesystem you like on them. My favorite fstype still is ext4, but you can choose others such as btrfs, jfs, or xfs. Setup will proceed as usual, but when you get to the point where you are presented with the lilo configuration dialog, it is almost time to perform one final manual tweak. Proceed with configuring your lilo as usual, and select '/dev/myvg/root' as your root filesystem to boot. When you install lilo, it will probably not complain, but be aware that having your root filesystem on a Logical Volume requires an initial ramdisk (initrd). The Slackware installer will not create it for you, and this requires some manual intervention after the setup program has finished and you've been returned to the command prompt. For now, you can continue with the Slackware setup as usual, but at the end, do not reboot just yet! At the end of the setup program it will prompt you to select "EXIT" and press 'Ctrl-Alt-Del' to reboot the computer. Exit the menu but DO NOT reboot just yet! At this point, we are going to create our initrd image. Fortunately, the Slackware installer has done some of the work for us. It will have created the LVM device nodes which lilo needs in order to install successfully. The installer will have mounted the /sys and /proc filesystems as well. Inside a 'chroot' we will create an initrd image and configure lilo to use it with the generic kernel. We are going to 'chroot' into our fresh installation: # chroot /mnt Next, while we are in the chroot, create the initrd with LVM support - in the example command line I assume that the root filesystem is 'ext4', we used the LV '/dev/myvg/root' as the root device, and are running the Slackware 15.0 default SMP kernel '5.15.19-smp': # mkinitrd -c -k 5.15.19-smp -m ext4 -f ext4 -r /dev/myvg/root -L The resulting initrd image will be written to the file '/boot/initrd.gz' by default. We still need to tell lilo about this initrd, so open the configuration file '/etc/lilo.conf' in an editor such as vi or pico - it should already have been generated by the 'liloconfig' part of setup. Look for the "Linux bootable partition config" and add a line for the initrd. Additionally, we change the filename of the kernel to be used. The default filename added by 'liloconfig' is '/boot/vmlinuz' which is a symbolic link to the huge SMP kernel. Remember that we need a 'generic' kernel with the initrd. The end result should look somewhat like this: image = /boot/vmlinuz-generic-smp-5.15.19-smp initrd = /boot/initrd.gz root = /dev/myvg/root label = linux read-only Double-check that the label you are using ('linux' in the above example) is unique in the /etc/lilo.conf file. If you are satisfied that everything looks OK, write the changes, exit the editor and (re-) run lilo while 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. ===================================================================== An alternative method of creating the commandline for mkinitrd is to use the '/usr/share/mkinitrd/mkinitrd_command_generator.sh' script which is part of the mkinitrd package. This script will analyze your Slackware installation and show you a useable 'mkinitrd' commandline: # /usr/share/mkinitrd/mkinitrd_command_generator.sh -r The above command would emit a commandline (almost) exactly as I showed earlier in this README. If you are satisfied that it is the correct command for you, then there is no need to type it manually; just enclose the above line in "$()" which will actually run the command and create your initrd: # $( /usr/share/mkinitrd/mkinitrd_command_generator.sh -r ) All that is left then is to update /etc/lilo.conf and run 'lilo'. ===================================================================== You're done in the chroot now. Exit the chroot by running the command 'exit' and return the original console prompt (not that this looks any different from the prompt inside the 'chroot' environment!). This completes the installation of Slackware. Good luck with your fresh 'Slackware with a root filesystem-on-LVM' ! A word about using a Logical Volume for SWAP -------------------------------------------- The setup program is able to detect a Logical Volume and use it as a swap partition, on the condition that you have manually formatted the LV as swap before you start 'setup'. That way, you will be able to select it as a usable swap partition in the ADDSWAP section. The setup program will inspect all your logical volumes for a swap header. Here is how you create the LV, assuming you already created the Volume Group 'myvg' earlier - see above - and left enough unallocated space in that VG: # lvcreate -L 1G -n swap myvg This command creates a 1 GB large Logical Volume called 'swap' (but any name will do) in the 'myvg' Volume Group. Next, format the volume for use as swap partition: # mkswap /dev/myvg/swap This is enough to get it recognized by the setup program. Have fun! ======================================================== Author: Eric Hameleers 13-oct-2013 Wiki URLs: http://www.slackware.com/~alien/dokuwiki/doku.php?id=slackware:setup Documentation: /usr/doc/Linux-HOWTOs/LVM-HOWTO