Gentoo Linux LiveUSB HOWTO
This HOWTO explains how to create a Gentoo Linux LiveUSB or, in other
words, how to emulate an x86 or AMD64 Gentoo Linux LiveCD using a USB flash
drive. This is particularly useful for installing Gentoo Linux on a modern
laptop with no CD-ROM drive.
The sys-boot/unetbootin package provides a much easier alternative to
create a bootable USB stick from any bootable CD image.
Although the instructions found in this document aim at emulating a Gentoo
Linux LiveCD using a USB flash drive, they should work for any arbitrary block
device as long as you adjust the device names accordingly.
In order to use a Gentoo Linux LiveUSB you need the following:
- Bootable USB flash drive with at least 1GB
- i686 or x86_64 computer with support for booting from USB
You will also need access to the following for creating the LiveUSB:
A computer running Gentoo Linux (or alternatively another Linux
Preparing the USB flash drive
Partitioning the drive
These instructions will erase all data from the USB flash drive. Make sure to
backup your data first.
This HOWTO assumes that the /dev/sdc device node corresponds to
your USB flash drive. If you have other SCSI-like devices make sure to use the
correct device node.
Create a FAT16 partition on your USB flash drive and mark it bootable using
fdisk. An example partitioning scheme can be seen below:
If your key is 4GB or larger, use partition type b (W95 FAT32).
Code Listing 2.1: Example partitioning scheme
# fdisk -l /dev/sdc
Disk /dev/sdc: 2063 MB, 2063597056 bytes
255 heads, 63 sectors/track, 250 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdc1 * 1 250 2008124+ 6 FAT16
Creating the filesystem
Create a FAT16 filesystem on the USB flash drive using mkdosfs:
If your key is 4GB or larger, use -F 32 to create a FAT32 filesystem.
Code Listing 2.2: Running mkdosfs
# emerge -av sys-fs/dosfstools
# mkdosfs -F 16 /dev/sdc1
mkdosfs 2.11 (12 Mar 2005)
Installing a Master Boot Record
Install the precompiled Master Boot Record (MBR) from syslinux on the
USB flash drive:
Code Listing 2.3: Installing a master boot record
# emerge -av '>sys-boot/syslinux-3'
# dd if=/usr/share/syslinux/mbr.bin of=/dev/sdc
0+1 records in
0+1 records out
304 bytes (304 B) copied, 0.0162317 s, 18.7 kB/s
Copying the files to your key
Mounting the Gentoo Linux Installation CD
Download the Gentoo Weekly Minimal Install CD for your architecture from your
local Gentoo Linux mirror site and mount
the ISO image on /mnt/cdrom as shown below:
Code Listing 3.1: Mounting the Gentoo Linux Installation CD ISO image
# mkdir -p /mnt/cdrom
# mount -o loop,ro -t iso9660 /path/to/iso.iso /mnt/cdrom
If you receive a Could not find any loop device error message when
mounting the iso, you need to enable the Loopback device support option
in your kernel configuration.
Mounting the LiveUSB
Mount the newly formatted USB flash drive on /mnt/usb as shown
Code Listing 3.2: Mounting the USB flash drive
# mkdir -p /mnt/usb
# mount -t vfat /dev/sdc1 /mnt/usb
Copying the files
Copy the files from the Gentoo Linux Installation CD to the LiveUSB. The files
need to be reordered a bit as we will be using the syslinux bootloader
instead of isolinux:
Code Listing 3.3: Copying the files
# cp -r /mnt/cdrom/* /mnt/usb
# mv /mnt/usb/isolinux/* /mnt/usb
# mv /mnt/usb/isolinux.cfg /mnt/usb/syslinux.cfg
# rm -rf /mnt/usb/isolinux*
# mv /mnt/usb/memtest86 /mnt/usb/memtest
You can now unmount the ISO image:
Code Listing 3.4: Unmounting the ISO image
# umount /mnt/cdrom
Adjusting the bootloader configuration
Adjust the syslinux configuration file using sed as shown below. The
slowusb parameter will introduce some extra delays before attempting to
mount the filesystem. This is needed to allow the USB flash drive to settle
Code Listing 3.5: Adjusting the boot parameters
# sed -i \
-e "s:cdroot:cdroot slowusb:" \
-e "s:kernel memtest86:kernel memtest:" \
Installing a bootloader
Unmounting the drive
Make sure you unmount the USB flash drive before installing the bootloader:
Code Listing 4.1: Unmounting the USB flash drive
# umount /mnt/usb
Finally install the syslinux bootloader on the USB flash drive:
Code Listing 4.2: Running syslinux
# syslinux /dev/sdc1
You will need to rerun syslinux /dev/sdc1 each time you modify the
syslinux.cfg file for the configuration changes to take affect.
If this is the first time you have used syslinux, you will need to edit
/etc/mtools/mtools.conf on your host. Simply commenting out
SAMPLE FILE will suffice for the purpose of this guide.
Using the LiveUSB
Insert the USB flash drive and turn on the computer, making sure the BIOS is
set to boot from USB. If all goes well you should be presented with a standard
You should be able to follow the generic installation instructions found in the
Gentoo Handbook from here on.
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