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Due to the limited space of the SDD inside the EeePC (8GB at most these days), and because most of these SDDs are not upgradable without voiding your warranty, there exists a challenge amongst those of us who yearn for more space, but do not wish to void our warranty. This solution uses an SD Card to basically expand the internal SDD storage, yet still present a coherent filesystem to the Linux OS.
This guide is intended for those who want to setup their system to be the most flexible and are going to be installing a different flavour of Linux anyways.
While it is likely possible to perform this operation on an already installed Linux distro, the process can be difficult (compounded by the fact that the older EEE's have little extra space). The basic steps would be to use gparted (or similar) to shrink your root partition to small enough (you will need to transfer a complete copy of your files from the EEE to a USB key or network share or something), follow the relevant parts of this guide to setup the logical volumes. Next restore your backup over the mounted root and lvm volumes, edit fstab, ensure that LVM2 is installed on your system and that your kernel supports it. Finally, reboot and hope for the best.
In this document, I expect that the reader has basic understanding of the following. If not, then maybe someone will update this tutorial for you, but for now, you need to understand:
* using disks by their device nodes * partitioning:
* creating filesystems on a partition
The following are things that you need to be aware of before you start:
If you don't know what LVM (logical volume management) is then it is highly recommended that you read Redhat's excellent introduction at http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/sysadmin-guide/ch-lvm-intro.html before continuing.
You will need the following in order to complete this setup:
WARNING this process will destroy all data currently residing on the SDD and SDHC card or USB stick you are using as an extra drive. Make sure you back up the contents of these first.
~ # sudo apt-get install lvm2
. Gentoo and Debian have these already installed.
~ # lsmod | grep dm_mod
~ # modprobe dm_mod
and execute the previous step to ensure the module was loaded.
~ # fdisk -l
You will get output similar to the following (NOTE: this is my output after setting up LVM. If someone has an example with the original partitions, feel free to place it here, instead of mine):
Disk /dev/sda: 4001 MB, 4001292288 bytes 255 heads, 63 sectors/track, 486 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00058e84 Device Boot Start End Blocks Id System /dev/sda1 * 1 32 257008+ 83 Linux /dev/sda2 33 95 506047+ 82 Linux swap / Solaris /dev/sda3 96 486 3140707+ 8e Linux LVM Disk /dev/sdb: 8195 MB, 8195670016 bytes 253 heads, 62 sectors/track, 1020 cylinders Units = cylinders of 15686 * 512 = 8031232 bytes Disk identifier: 0x000659d3 Device Boot Start End Blocks Id System /dev/sdb1 1 1020 7999829 8e Linux LVM
I can tell that /dev/sda is the internal SSD because of the size (4GB). /dev/sdb is obviously the SDHC card because of it's size (8GB). These device nodes may or may not be the same, depending upon how you booted and you may see other devices as well (for example if you booted from a USB stick, you may see another /dev/sdX device).
|Mount point||Partition Type||Notes||Recommended size for Debian|
|/||physical||Although possible booting with a root or boot FS on LVM is out of scope for this tutorial.||128MB (without seperate /boot), 100MB (with separate /boot)|
|/boot||physical||Optional, but a good idea for extra security, because you won't mount it unless you explicitly need to change something. I do this on Gentoo, but not on Debian/Ubuntu, because on the latter an initramfs is used and will be updated when certain packages are installed. On Gentoo I use a custom kernel without an initramfs, so I only need to mount this partition when I recompile the kernel.||30MB|
|/var||LVM||Debian uses a lot of space initially in /var for temporary storage of install files, this can be resized if you distribution is not Debian based, or uses less /var space on installation.||1.5 GB|
|/usr||LVM||This is where most programs are installed to on most Linuxes. This figure will vary slightly depending upon Desktop choice and application choice||2.0 GB (I am using 60% of this with a very basic KDE installation)|
|/opt||LVM||This is where external third-party components generally go. With Debian based stuff, I haven't had a lot of stuff go here. With Gentoo, if source hasn't been available for a package, pre-compiled packages willgenerally go here.||100 MB|
|/home||LVM||unneeded for installation, but is best to create it at installation so that you don't have to move files around later.||At least 5MB/user for personalized KDE settings, 2MB for personalized Gnome settings. If you are running a Firefox based browser, then add 40-50M/user (why? read this). Other applications will require more.|
|swap||physical or LVM||If you want to take a crack at getting suspend/hibernate working, then make this physical and at least the size of your RAM. Otherwise it is optional and depends only on what you run. I have 512MB of RAM and have yet to have my machine ever swap out. I have successfully run||See notes.|
|/tmp||LVM or tmpfs||Pick LVM if you have a distro that likes temp space or want your /tmp to persist through reboots.||I use tmpfs and am currently utilizing only 36K|
|/var/log||LVM or tmpfs||tmpfs is a pain if you need to do kernel debugging, etc as the directory is reset on each reboot.||I use tmpfs and am currently utilizing only 200K|
|/var/tmp||LVM or tmpfs||Pick LVM if you have a distro that likes temp space or wants/needs your /var/tmp to persist through reboots.||I use tmpfs and am currently utilizing only 1.1MB|
At this point we are ready to setup the LVM and partitioning scheme. You will be creating physical partitions for any drive that is marked physical above. Remember that each drive can only have 4 primary partitions, if you need more then you'll need to create extended partitions under one of the primaries. I highly recommend that you place / and /boot on your SSD, as booting will be much faster from this media. If you are going with physical swap, then either the SSD or SDHC will work (SSD is probably better as it is a faster device). In my setup, I am using a physical / and an lvm swap. The rest of the space is setup for LVM.
So now you have figured out what your plan is (which mountpoints are physical and which are logical volumes). The next thing to do is to create the partitions for your physical volumes and one for each disk that needs to be part of LVM.
In my situation, the only mount point I had chosen to be physical was /. The rest of my disk space is going to be used by logical volumes. So I have created a 256M primary partion on my SSD (/dev/sda for me) as type 83 (Linux) and the rest was allocated to a second primary partition with type 8E (Linux LVM). I partitioned the SDHC card as a single primary partition with type 8E.
The last step before finishing your installation is to set up LVM. Before we start, here are some terms you need to be aware of: * Physical Volume - AKA pv - These are the physical partitions that will be used for hosting the lvm volumes. * Volume Group - AKA vg - this a group of physical volumes that are grouped together to look like a single disk * Logical Volume - AKA lv - this is a “partition” on the volume group. To the OS, it looks and behaves like a normal disk, although there may be a number of actual disks (PVs) supporting an LV.
The first step is to ensure that the correct modules are loaded into the kernel and that the tools are available in your environment: - Ensure that mod_dm is loaded:
modprobe | grep mod_dm
If something is returned, then it is loaded. If not continue. - Load it is it isn't:
Some installation environments may or may not have the lvm2 tools installed. Debian and Gentoo install disks include them. Ubuntu does not. On Ubuntu simply run
sudo apt-get install lvm2
Next we need to tell the device mapper (mod_dm) and the lvm tools about the PVs we will be using. To do this we will call the pvcreate command.
# pvcreate <partition device>
Where <partition device> is the device node, such as /dev/sda2, that will be used for LVM. We need to call this command once for each partition that we want in the logical volume array.
Now we need to create a VG that maps the LVs to the PVs on which they will actually be stored. The volume group is conceptually just a big area of unpartitioned disk space that logical volumes are carved out of (LVs are like partitions). You can have multiple VGs if you wish, but for most desktop installs, there is not much of a reason to go with more than one. To create this volume group, we use the vgcreate command.
# vgcreate <vg name> <device1> <device2> ... <deviceN>
Where <vg name> is the name you wish to refer to this volume group by. It can be anything that is supported by a regular file name, but I suggest you keep it short and sweet, as it creates a device node called /dev/<vg name>. I called mine “vol1”. The device parameters are the space delimited list of PVs that will support the volume group. I used /dev/sda2 and /dev/sdc1.
As a quick aside, you can set up LVM just on your SSD right now and not worry about the SDHC card. You can do this if you do not have an SDHC card at the moment, or if you want to ensure the base install is definately installed on the SSD. When you wish you can add the SDHC card later by inserting it and issuing the following command (make sure the SDHC is NOT mounted though):
# pvcreate <device> # vgmodify --add <device>
Where device is of course the device node of the LVM partition on the SDHC card.
Okay, so now we have consolidated all of our physical partitions (PVs) to appear as one (a VG). Now we need to carve up that VG into its own partitions, called logical volumes (LVs). It is these LVs that will have the filesystems written to them, and which will be mounted to the mount points. To create a logical volume we use…you guessed it! lvcreate:
# lvcreate <some options>
You need to run this command once for each LV you want (refer to your planning table). Here are the commands I issued for my device.
At this point we need to continue with the installation of the OS.
As each installer is different, the actual steps will be different for each linux flavour, however they all will end up doing the same things: - Format the each LV with the appropriate filesystem - Mount each LV to the place it is supposed to reside with on the end system - Install the components of the OS - Compile the kernel with device mapper and LVM support, or update the initramfs to support this - Update the target system's /etc/fstab to mount these logical volumes on boot
During this phase, you will need to determine which File system you are are going to use for each LV. Here are a list of the currently popular filesystems and how they relate to LVM and the EEE: * ext2 - supports growing and shrinking, and as such is a a decent choice for LVM, however, it does not journal, and has a number of other limitations, so I personally do not recommend it for an EEE. * ext3 - supports growing and shrinking. Because it journals it is a better choice for an EEE, however I find that EXT3's implementation of journalling eats up too much disk space for such a small disk, so I avoid it. * reiserfs 3 - supports growing and shrinking. It also journals, and has less journalling overhead than ext3. Unfortunately, it was written by a convicted murderer. It is currently my choice for now, due to limitations of other journalling file systems. * JFS and XFS - supports growing the FS. Has less journalling overhead than reiserfs. Because I like to reclaim disk space occasionally (I am a tinkerer), I don't use this filesystem because I can't shrink it. If there ever is shrinking support, I'll probably move away from reiser.
I have experience with the top three filesystems in this list and have never lost data due to a bug in any of them (and in fact have not yet lost data in EXT3 and Reiser thanks to journalling) and they are all stable and well supported byt the major distros. JFS and XFS look extremely interesting and promising to me, but because of the lack of shrink capabilities, I have not used them in any significant fashion. Others feel free to post your experiences on JFS and XFS here.
There are other up and coming filesystems (ext4, brtfs and arguably reiser4), but I have no experience with these so cannot comment.
insert OS specific instructions here