Installing Arch Linux on a USB key

This page explains how to perform a regular Arch installation onto a USB key (or "flash drive"). In contrast to having a LiveUSB as covered in USB Installation Media, the result will be a persistent installation identical to normal installation to HDD, but on a USB flash drive.

Preparation

Note: At least 2 GiB of storage space is recommended. A modest set of packages will fit, leaving a little free space for storage.

There are various ways of installing Arch on a USB stick, the simplest being from within Arch itself:

• If you are already running Arch, simply install arch-install-scripts and proceed with the Installation Guide just like you would from the iso, but you will not be using /dev/sda. Use $ lsblk to get the /dev/sd* name of your USB key prior to installation.

Warning: If you mistakingly format /dev/sda, you are likely to go about deleting everything on your hard drive.

• An Arch Linux CD/USB can be used to install Arch onto the USB key, via booting the CD/USB and following the Installation Guide. If booting from a Live USB, the installation will have to be made on a different USB stick.
• Or, if you have another Linux computer available (it need not be Arch), you can follow the instructions to install from existing Linux, and then skip to the configuration section.

Installation

Follow the Installation Guide as you normally would, with these exceptions:

• If cfdisk fails with "Partition ends in the final partial cylinder" fatal error, the only way to proceed is to kill all partitions on the drive. Open another terminal (Template:Keypress), type fdisk /dev/sdX (where sdX is your usb drive), print partition table (p), check that it's ok, delete it (d) and write changes (w). Now return to cfdisk.
• It is highly recommended to review the Tips for Minimizing SSD Read/Writes on the SSD wiki article prior to selecting a filesystem. To sum up, ext4 without a journal should be fine. Recognize that flash has a limited number of writes, and a journaling file system will take some of these as the journal is updated. For this same reason, it is best to forgo a swap partition. Note that this does not affect installing onto a USB hard drive.
• Before creating the initial RAM disk # mkinitcpio -p linux, in /etc/mkinitcpio.conf add the block hook to the hooks array right after udev. This is necessary for appropriate module loading in early userspace.

Configuration

• Make sure that /etc/fstab includes the correct partition information for /, and for any other partitions on the USB key. If the usb key is to be booted on several machines, it is quite likely that devices and number of available hard disks vary. So it is advised to use UUID or label:

To get the proper UUIDs for your partitions issue blkid

Note:

• When GRUB is installed on the USB key, the key will always be hd0,0.
• It seems that current versions of GRUB will automatically default to using uuid. The following directions are for GRUB legacy.

GRUB legacy

menu.lst, the GRUB legacy configuration file, should be edited to (loosely) match the following: With the static /dev/sdaX:

root (hd0,0)
kernel /boot/vmlinuz-linux root=/dev/sda1 ro
initrd /boot/initramfs-linux.img

When using label your menu.lst should look like this:

root (hd0,0)
kernel /boot/vmlinuz-linux root=/dev/disk/by-label/Arch ro
initrd /boot/initramfs-linux.img

And for UUID, it should be like this:

root (hd0,0)
kernel /boot/vmlinuz-linux root=/dev/disk/by-uuid/3a9f8929-627b-4667-9db4-388c4eaaf9fa ro
initrd /boot/initramfs-linux.img

Syslinux

With the static /dev/sdaX

LABEL Arch
        MENU LABEL Arch Linux
        LINUX ../vmlinuz-linux
        APPEND root=/dev/sdax ro
        INITRD ../initramfs-linux.img

Using your UUID:

LABEL Arch
        MENU LABEL Arch Linux
        LINUX ../vmlinuz-linux
        APPEND root=UUID=3a9f8929-627b-4667-9db4-388c4eaaf9fa ro
        INITRD ../initramfs-linux.img

Tips

Using your USB install on multiple machines

Architecture

For the most versatile compatibility it is recommended that you install the x86_64 architecture with multilib support because it will run on both 32 and 64 bit architectures.

Note: If you have installed i686 architecture and would like to migrate to x86_64, please refer to the Migrating Between Architectures Without Reinstalling wiki article for help.

Input drivers

For laptop use (or use with a tactile screen) you will need the xf86-input-synaptics package for the touchpad/touchscreen to work.

For instructions on fine tuning or troubleshooting touchpad issues, see the Touchpad Synaptics article.

Video drivers

Note: The use of proprietary video drivers is not recommended for this type of installation.

The recommended video drivers are: xf86-video-vesa mesa xf86-video-ati xf86-video-intel xf86-video-nouveau xf86-video-nv.

For the most versatile compatibility install all of the open source video drivers include their multilib counterparts: lib32-ati-dri lib32-intel-dri lib32-nouveau-dri.

Boot without using UUID

When using the USB key on various target machines, it is helpful to have multiple entries in GRUB, for machines with different setups. For example, the GRUB configuration could contain:

# (0) Arch Linux
title  Arch Linux (first drive)
root   (hd0,0)
kernel /boot/vmlinuz-linux root=/dev/sda1 ro
initrd /boot/initramfs-linux.img

As well as

# (1) Arch Linux
title  Arch Linux (second drive)
root   (hd0,0)
kernel /boot/vmlinuz-linux root=/dev/sdb1 ro
initrd /boot/initramfs-linux.img

And so forth, giving you the option to select a configuration for a wider variety of machines. However, changing the root= option in GRUB does not change /etc/fstab and you must do something (in our example using udev symlink), so the root partition will always be mounted correctly.

• Run udevinfo -p /sys/block/sdx/ -a (where sdx is the device name of your usb key)
• Find unique information pertaining to your usb key. I chose SYSFS{model}=="DataTraveler 2.0"
• Make a new file: /etc/udev/udev.rules/10-my-usb-key.rules and insert:

KERNEL=="sd**", SYSFS{product}=="DataTraveler 2.0", SYMLINK+="WHATEVERYOUWANTOTCALLIT%n"

(KERNEL=="sd**" is because the kernel - 2.6.16 here - names all usb devices sd as it uses the scsi sub-system and you want to look at every sd device and apply the setting to every partition), with SYSFS{model}== being the unique identifier collected from udevinfo.

• Run /etc/start-udev uevents and make sure the symlinks appears in /dev.
• If so, edit /etc/fstab, replacing your old sdx with the new symlinks.

Kernel parameters

You may want to disable KMS for various reasons, such as getting a blank screen or a "no signal" error from the display, when using some Intel video cards, etc. To disable KMS, add nomodeset as a kernel parameter. See Kernel parameters for more info.

Warning: Some Xorg drivers will not work with KMS disabled. See the wiki page on your specific driver for details. Nouveau in particular needs KMS to determine the correct display resolution. If you add nomodeset as a kernel parameter as a preemptive measure you may have to adjust the display resolution manually when using machines with Nvidia video cards. See Xrandr for more info.

Optimizing for the lifespan of flash memory

• Again, it is highly recommended to review the Tips for Minimizing SSD Read/Writes on the SSD wiki article.

See also

• Official Arch Linux Install Guide
• Installing Arch Linux from VirtualBox
• Solid State Drives