LiveUSB/ISOLINUX

As of 2023-07-20, the information in this article has been deprecated. It may or may not be relevant for contemporary usage. Handle with care!

Important
As of 2020, official Gentoo live images are no longer based on ISOLINUX, therefore the instructions in this article are deprecated. They still may be useful for other distributions which utilize ISOLINUX or when using ancient Gentoo live images. See LiveUSB instead.

This article details creating a bootable LiveUSB drive from a ISOLINUX-based live image.

Automatic drive-wide installation script

Warning
This script will erase all data from the USB drive. Make sure to backup any pre-existing data first, and always backup all important data.

Important
This article assumes that the supplied device node corresponds to the USB drive. If other SCSI-like devices exist be sure to use the correct device node. Major data loss could occur if the wrong device node is selected!

This script will assist in writing a LiveUSB stick suitable for both BIOS and UEFI systems.

FILE gentoo-usb.sh

#!/bin/bash
set -e
image=${1:?Supply the .iso image of a Gentoo installation medium}
target=${2:?Supply the target device}

echo Checking for the necessary tools presence...
which syslinux
which sfdisk
which mkfs.vfat

echo Mounting Gentoo CD image...
cdmountpoint=/mnt/gentoo-cd
mkdir -p "$cdmountpoint"
trap 'echo Unmounting Gentoo CD image...; umount "$cdmountpoint"' EXIT
mount -o loop,ro "$image" "$cdmountpoint"

echo Creating a disk-wide EFI FAT partition on "$target"...
echo ',,U,*' | sfdisk --wipe always "$target"

echo Installing syslinux MBR on "$target"...
dd if=/usr/share/syslinux/mbr.bin of="$target"
sleep 1

echo Creating file system on "$target"1...
mkfs.vfat "$target"1 -n GENTOO

echo Mounting file system...
mountpoint=/mnt/gentoo-usb
mkdir -p "$mountpoint"
mount "$target"1 "$mountpoint"

echo Copying files...
cp -r "$cdmountpoint"/* "$mountpoint"/
mv "$mountpoint"/isolinux/* "$mountpoint"
mv "$mountpoint"/isolinux.cfg "$mountpoint"/syslinux.cfg
rm -rf "$mountpoint"/isolinux*
mv "$mountpoint"/memtest86 "$mountpoint"/memtest
sed -i -e "s:cdroot:cdroot slowusb:" -e "s:kernel memtest86:kernel memtest:" "$mountpoint"/syslinux.cfg

echo Unmounting file system...
umount "$mountpoint"

echo Installing syslinux on "$target"1
syslinux "$target"1

echo Syncing...
sync

echo 'Done!'

Manually preparing a LiveUSB drive

Preparing the USB drive

Partitioning the drive

Warning
These instructions will erase all data from the USB drive. Make sure to backup any pre-existing data first.

Important
This article assumes that the /dev/sdc device node corresponds to the USB drive. If other SCSI-like devices exist be sure to use the correct device node to prevent data loss!

Create a FAT16 partition on the USB drive and mark it bootable using fdisk. An example partitioning scheme can be seen below:

Note
If the USB drive is 4GB or larger, use partition type b (W95 FAT32).

root #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 drive using mkfs.fat:

Note
If the drive is 4GB or larger, use -F 32 to create a FAT32 filesystem.

root #emerge --ask sys-fs/dosfstools

root #mkfs.fat -F 16 /dev/sdc1

mkfs.fat 3.0.22 (2013-07-19)

Installing a Master Boot Record (MBR)

Install the precompiled Master Boot Record (MBR) from syslinux on the USB drive:

root #emerge --ask --verbose sys-boot/syslinux

root #dd if=/usr/share/syslinux/mbr.bin of=/dev/sdc

0+1 records in
0+1 records out
440 bytes (440 B) copied, 0.00522668 s, 84.2 kB/s

Copying the files

Mounting the Gentoo Minimal Installation CD

Download a Gentoo Minimal Installation CD for the system's architecture from a the main site's download page and mount the ISO image on /mnt/cdrom as shown below:

root #mkdir -p /mnt/cdrom

root #mount -o loop,ro -t iso9660 /path/to/isofile.iso /mnt/cdrom

Adjust the /path/to/isofile.iso as necessary to the location of the downloaded Minimal Installation CD ISO.

Note
If a "Could not find any loop device" error message is displayed when mounting the ISO, a kernel recompile may be required. Verify the Loopback device support option in the kernel configuration has been enabled. For more information on kernel configuration see the kernel configuration article.

Mounting the LiveUSB

Mount the newly formatted USB drive on /mnt/usb as shown below:

root #mkdir -p /mnt/usb

root #mount -t vfat /dev/sdc1 /mnt/usb

Copying the files

Copy the files from the Minimal Installation CD to the LiveUSB. The files need to be reordered since syslinux will be used as the bootloader instead of isolinux:

root #cp -r /mnt/cdrom/* /mnt/usb

root #mv /mnt/usb/isolinux/* /mnt/usb

root #mv /mnt/usb/isolinux.cfg /mnt/usb/syslinux.cfg

root #rm -rf /mnt/usb/isolinux*

root #mv /mnt/usb/memtest86 /mnt/usb/memtest

Unmount the ISO image:

root #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 drive to settle upon detection.

root #sed -i -e "s:cdroot:cdroot slowusb:" -e "s:kernel memtest86:kernel memtest:" /mnt/usb/syslinux.cfg

Installing a bootloader

Unmounting the drive

Make sure the USB drive has been unmounted before installing the bootloader:

root #umount /mnt/usb

Installing syslinux

Finally install the syslinux bootloader on the USB drive:

root #syslinux /dev/sdc1