Install Gentoo on a bootable USB stick/cs
Booting Gentoo from a USB stick is really quite simple. The main challenge is to setup an initial ramdisk and to include the drivers for all the machines it is going to boot. This article describes how to install Gentoo onto a USB stick that can be booted on any computer. This installation will be just like a regular desktop installation and changes will be persistent.
This article covers installation of a complete, functional, Gentoo system onto a USB drive. See the LiveUSB article for instructions on creating a simple bootable drive, that can for example be used for Gentoo installation.
Preparation
The guide assumes that the current platform is a Gentoo Linux one. The majority of steps however can be performed from any distribution, just translate the Gentoo-specific way of doing things (such as installing software) to the other distribution's practices.
Start by installing a couple of necessary packages. Most importantly these are a kernel and the sys-kernel/genkernel package:
root #
emerge --ask sys-kernel/gentoo-sources sys-kernel/genkernel
Compiling the kernel
Make the required changes to the kernel and compile it. Please see Configuring the Linux kernel and the kernel configuration guide for more detail on this step. Importantly remember that a general kernel is better here because the more general it is the more machines will boot with it.
During the configuration, it is of course possible to compile modules as these will be included in the initramfs and loaded at boot.
root #
mkdir /tmp/boot
root #
genkernel --firmware --bootdir=/tmp/boot --no-symlink --all-ramdisk-modules --install all
The above command will take some time as it will build the default kernel, create a ramdisk and then copy all files into /tmp/boot.
root #
ls /tmp/boot/
initramfs-genkernel-x86_64-3.5.2-gentoo kernel-genkernel-x86_64-3.5.2-gentoo System.map-genkernel-x86_64-3.5.2-gentoo
Preparing the USB stick
Create 2 partitions on the drive (assuming the installation will have a /boot and a / (root) partition). We assume that the USB stick is at /dev/sdb (run dmesg immediately after plugging in the USB stick to see which device is being used).
root #
fdisk /dev/sdb
Command (m for help): d Selected partition 1 Command (m for help): n Partition type: p primary (0 primary, 0 extended, 4 free) e extended Select (default p): p Partition number (1-4, default 1): 1 First sector (2048-4001759, default 2048): Using default value 2048 Last sector, +sectors or +size{K,M,G} (2048-4001759, default 4001759): +100M Command (m for help): n Partition type: p primary (1 primary, 0 extended, 3 free) e extended Select (default p): p Partition number (1-4, default 2): Using default value 2 First sector (206848-4001759, default 206848): Using default value 206848 Last sector, +sectors or +size{K,M,G} (206848-4001759, default 4001759): Using default value 4001759 Command (m for help): a Partition number (1-4): 1 Command (m for help): p Disk /dev/sdb: 2048 MB, 2048901120 bytes 255 heads, 63 sectors/track, 249 cylinders, total 4001760 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x001663df Device Boot Start End Blocks Id System /dev/sdb1 * 2048 206847 102400 83 Linux /dev/sdb2 206848 4001759 1897456 83 Linux Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
Make sure that the first partition is bootable (a
command toggles the boot flag).
Now format the new partitions. In the example we use the ext2 file system but another file system for the / partition can be used if it is supported in the kernel. Notice that during the formatting operation, a label is assigned to the partitions. This is important because it will be how the root file system is detected later as the USB stick can be booted on systems where the drive letter allocation is completely different.
root #
mkfs.ext2 -L GENTOO_USB_BOOT /dev/sdb1
root #
mkfs.ext2 -L GENTOO_USB_ROOT /dev/sdb2
Gentoo stage 3 installation
With the kernel, ramdisk and file systems ready, we now need the minimal installation to be performed. This includes a fresh stage3 as well as a Portage tree snapshot.
For this example stage3-amd64-20120621.tar.bz2 and portage-latest.tar.xz are used. This next bit is the same as in the handbook for installing Gentoo.
root #
mount /dev/sdb2 /mnt/gentoo
root #
cd /mnt/gentoo
root #
tar -xpf ~/Download/stage3-amd64-20120621.tar.bz2
root #
cd usr
root #
tar -xpf ~/Download/portage-latest.tar.xz
root #
mount /dev/sdb1 /mnt/gentoo/boot
root #
cp /tmp/boot/* /mnt/gentoo/boot
The sections below cover those aspects of a Gentoo Linux installation that are specific to installing on an USB stick. It is recommended to use the Gentoo handbook instructions while keeping an eye on this article.
Bootloader
In order to boot the new system, install a bootloader on the USB stick.
Sekce níže ukazuje příklady konfiguraci pro GRUB nebo používání lilo společně s syslinux.
GRUB
This method only applies to UEFI booting!
Emerge GRUB (zevnitř prostředí chroot):
(chroot) #
emerge sys-boot/grub
Install GRUB to the corresponding place with your platform information. Suppose you are running a x86_64 machine with an EFI partition mounted to /boot/efi, the following command will install GRUB onto the USB stick:
(chroot) #
grub-install --efi-directory=/boot/efi --target=x86_64-efi --removable
Note that the
--removable
option is very important. It indicates that the target location is removable device. Don't forget it otherwise you may mess up your own system!If nothing bad happens, run grub-mkconfig to generate the GRUB configuration:
(chroot) #
grub-mkconfig -o /boot/grub/grub.cfg
Change the target directory accordingly if you use a different GRUB config directory.
lilo
Emerge lilo (zevnitř prostředí chroot):
(chroot) #
emerge sys-boot/lilo
Edit etc/lilo.conf aby v sobě soubor měl správné informace.
These settings are very important and will be discussed line by line.
/etc/lilo.conf
Configure lilo.confboot=/dev/sdb # The location of the USB Stick (currently)
lba32 # use lba32 addressing (ignore)
compact # boot quickly by loading lots of blocks
# remove when there are problems with booting
prompt # Prompt for user input
timeout=20 # Time to wait before default selection
default="Gentoo-352" # Default selection after timeout
image=/boot/vmlinuz-5.10.76-gentoo-r1-x86_64
label="Gentoo-352"
read-only
root=/dev/ram0
append="root=LABEL=GENTOO_USB_ROOT scandelay=5"
initrd=/boot/initramfs-5.10.76-gentoo-r1-x86_64.img
The lines after image are all easy but the append line contains some interesting options.
root=LABEL=GENTOO_USB_ROOT
bude používat název disku místo /dev/sdb2 což je důležité, protože pořadí disků se může změnit podle toho kolik disků a USB disků je připojeno k počítači.- Také důležité pro bootování z USB disku je možnost
scandelay
, protože USB disky potřebují o trochu více času aby byli detekovány kernelem. Když se při bootování načítá více modulů, bootování trvá delší dobu a v tomto případě by to nemuselo být důležité a možnost by mohla být vynechána, ale pokud načítáme jen pár modulů, možnost je důležitá, protože by systém mohl nabootovat předtím, než kernel detekuje USB zařízení. Na novějších zařízeních, které používají USB 3, je důležité aby se při bootu načetl driverxhci_hcd
(může být vestavěn přímo v kernelu, nebo se načítat jako modul)
Now install LILO (with the configuration) on the USB stick:
(chroot) #
lilo
Warning: /dev/sdb is not on the first disk Warning: The initial RAM disk is too big to fit between the kernel and the 15M-16M memory hole. It will be loaded in the highest memory as though the configuration file specified "large-memory" and it will be assumed that the BIOS supports memory moves above 16M. Added Gentoo-352 ? * 2 warnings were issued.
The first warning is to be expected as we are not installing the boot loader onto the hard disk in the computer. The second warning will only cause a problem on machines that are old; if it is a problem try cutting down the kernel by removing modules.
syslinux
syslinux currently only works with ext{2,3,4}, btrfs, ntfs and fat filesystems.
(chroot) #
emerge syslinux
Put the boot sector onto the USB stick.
(chroot) #
dd bs=440 count=1 conv=notrunc if=/usr/share/syslinux/mbr.bin of=/dev/sdb
Now to configure the bootloader.
(chroot) #
mkdir /boot/syslinux
(chroot) #
nano -w /boot/syslinux/syslinux.cfg
/boot/syslinux/syslinux.cfg
PROMPT 1
TIMEOUT 50
DEFAULT gentoo
LABEL gentoo
LINUX ../vmlinuz-5.10.76-gentoo-r1-x86_64
APPEND root=LABEL=GENTOO_USB_ROOT scandelay=3 ro
INITRD ../initramfs-5.10.76-gentoo-r1-x86_64.img
The
ro
in the above APPEND
line will cause the root partition to be mounted read-only (which is usually preferred on USB sticks). Replace ro
with rw
to allow the system to be modified from the boot onwards (instead of having the user mount the file system as read-write later).Next install syslinux onto the USB stick. The --device /dev/sdb1
option is not absolutely necessary though.
(chroot) #
extlinux --device /dev/sdb1 --install /boot/syslinux
fstab
/etc/fstab
Configure the fstab file to work with labelsLABEL=GENTOO_USB_BOOT /boot ext2 noauto,noatime 1 2
LABEL=GENTOO_USB_ROOT / ext2 noatime 0 1
/dev/SWAP none swap sw 0 0
/dev/cdrom /mnt/cdrom auto noauto,ro 0 0
/dev/fd0 /mnt/floppy auto noauto 0 0
Tips and tricks
Although it is possible to use the system just made as a standard Gentoo system, it might be worthwhile to compile binary packages on a host and then installing them on the USB stick. Or if the system has enough memory just mount /var/tmp to a tmpfs, as compilation will be much quicker that way anyway!
See also
- Installation — an overview of the principles and practices of installing Gentoo on a running system.
- LiveUSB — explains how to create a Gentoo LiveUSB or, in other words, how to emulate a x86 or amd64 Gentoo LiveCD using a USB drive.