Remastering the Install ISO
Remastering the official Arch Linux install ISO image is not necessary for most applications. However, it may be desirable in some cases.
- Basic hardware is not supported by the core install. (rare)
- Installation on a non-internet capable machine.
- Deployment of Arch Linux on many similar machines, requiring the same installation procedure.
As these ISOs are bootable, they can also be used for system rescue, testing, project demos, and more.
Contents
Archiso
It is often preferable to rebuild the installation ISO with Archiso, instead of remastering an existing ISO.
Manually
How it works
The root filesystems of the live system is stored in arch/x86_64/airootfs.sfs
in the ISO. The kernel and initramfs are in arch/boot/x86_64
.
When booting, the initramfs will search for the device it was booted from via its label, ARCH_201410
for example, and will mount the root filesystem for the architecture.
Extracting the ISO
To remaster the Arch Linux ISO, you will need a copy of the original ISO image. Download it from the download page
Now, create a new directory to mount the ISO:
# mkdir /mnt/archiso
Mount the ISO to this directory (due to the nature of ISOs, the result is read-only):
# mount -t iso9660 -o loop /path/to/archISO /mnt/archiso
Copy the contents to another directory, where they can be edited:
$ cp -a /mnt/archiso ~/customiso
customiso
does not exist beforehand, otherwise this will create a subdirectory called archiso
inside customiso
.Customization
Modifying the x86_64 system
Change into the directory of the x86_64 system:
$ cd ~/customiso/arch/x86_64
Unsquash airootfs.sfs
(to squashfs-root
):
$ unsquashfs airootfs.sfs
If you will need to run mkinitcpio
within arch-chroot
, you need to temporarily copy the kernel over:
$ cp ../boot/x86_64/vmlinuz squashfs-root/boot/vmlinuz-linux
Now you can modify the content of the system in squashfs-root
. You can also chroot into this system to install packages etc.:
# arch-chroot squashfs-root /bin/bash
-
arch-chroot
is part of the package arch-install-scripts. - If the
arch-chroot
script is not available in your system (e.g, when remastering from other distributions), mount the API file systems and copy over your DNS details. See Chroot#Using chroot.
To be able to install package, you have to initialise the pacman keyring:
(chroot) # pacman-key --init (chroot) # pacman-key --populate archlinux
If the kernel or initrd is updated, additional steps are required. In this case you have to install archiso inside the chroot and change the content of /etc/mkinitcpio.conf
:
(chroot) # pacman -Syu --force archiso linux (chroot) # nano /etc/mkinitcpio.conf
Change the line that says HOOKS="...
to:
HOOKS="base udev memdisk archiso_shutdown archiso archiso_loop_mnt archiso_pxe_common archiso_pxe_nbd archiso_pxe_http archiso_pxe_nfs archiso_kms block filesystems keyboard"
Now update the initramfs:
(chroot) # mkinitcpio -p linux
When you are done, create a list of all installed packages, clean the pacman cache and exit the chroot:
(chroot) # LANG=C pacman -Sl | awk '/\[installed\]$/ {print $1 "/" $2 "-" $3}' > /pkglist.txt (chroot) # pacman -Scc (chroot) # exit
If you updated the kernel or the initramfs, move them over to the system, and remove the fallback initramfs (the install ISO does not use this):
$ mv squashfs-root/boot/vmlinuz-linux ~/customiso/arch/boot/x86_64/vmlinuz $ mv squashfs-root/boot/initramfs-linux.img ~/customiso/arch/boot/x86_64/archiso.img $ rm squashfs-root/boot/initramfs-linux-fallback.img
Move the list of packages:
$ mv squashfs-root/pkglist.txt ~/customiso/arch/pkglist.x86_64.txt
Now recreate airootfs.sfs
:
$ rm airootfs.sfs $ mksquashfs squashfs-root airootfs.sfs
-comp xz
option on mksquashfs
to significantly reduce size, but it also takes longerCleanup:
# rm -r squashfs-root
Now update the SHA512 checksum of airootfs.sfs
:
$ sha512sum airootfs.sfs > airootfs.sha512
Modifying the EFI boot image
If you have updated the kernel or the initramfs and wish to boot on EFI systems, update the EFI boot image.
You will need dosfstools as the EFI boot image is a FAT16
filesystem.
$ mkdir mnt # mount -t vfat -o loop ~/customiso/EFI/archiso/efiboot.img mnt # cp ~/customiso/arch/boot/x86_64/vmlinuz mnt/EFI/archiso/vmlinuz.efi # cp ~/customiso/arch/boot/x86_64/archiso.img mnt/EFI/archiso/archiso.img
If you see No space left on device
errors, you might need to resize efiboot.img
.
You can also create a new efiboot.img
and copy the old files (replace 50
with the required size).
$ dd if=/dev/zero bs=1M count=50 of=efiboot-new.img $ mkfs.fat -n "ARCHISO_EFI" efiboot-new.img $ mkdir new # mount -t fat -o loop efiboot-new.img new $ cp -r mnt/* new/ # umount new mnt $ mv efiboot-new.img ~/customiso/EFI/archiso/efiboot.img
And use the new efiboot.img
as above.
Create a new ISO
Create a new ISO image with genisoimage
, which is part of cdrtools, as a symlink to mkisofs
.
$ genisoimage -l -r -J -V "ARCH_201209" -b isolinux/isolinux.bin -no-emul-boot -boot-load-size 4 -boot-info-table -c isolinux/boot.cat -o ../arch-custom.iso ./
- The ISO label must remain the same as the original label (in this case
ARCH_201209
) for the image to boot successfully. - The
-b
and-c
options expect paths relative to the root of the ISO.
The resulting ISO image will boot only from CD, DVD or BD. For booting from USB stick or hard disk, it needs the isohybrid feature.
This can be achieved by postprocessing the ISO by program isohybrid included in syslinux.
Officially, the version of installed SYSLINUX has to be the same as the version of /isolinux/isolinux.bin
in the ISO. It is not known whether really incompatible version combinations exist.
An alternative to genisoimage plus isohybrid can be derived from the xorriso run of mkarchiso.
$ iso_label="ARCH_201209" $ xorriso -as mkisofs \ -iso-level 3 \ -full-iso9660-filenames \ -volid "${iso_label}" \ -eltorito-boot isolinux/isolinux.bin \ -eltorito-catalog isolinux/boot.cat \ -no-emul-boot -boot-load-size 4 -boot-info-table \ -isohybrid-mbr ~/customiso/isolinux/isohdpfx.bin \ -output arch-custom.iso \ ~/customiso
Option -isohybrid-mbr
needs an MBR template file. Most probably there is already such a file /isolinux/isohdpfx.bin
in the original ISO, which matches the SYSLINUX version used in the ISO.
Only if this file is missing in the copied ISO content, it has to be cut out of the original ISO image file, before above xorriso run is performed:
$ dd if=/path/to/archISO bs=512 count=1 of=~/customiso/isolinux/isohdpfx.bin
If the original ISO supports bootability via EFI, this can be activated in the new ISO by inserting the following options between the lines -isohybrid-mbr ...
and -output ...
:
-eltorito-alt-boot \ -e EFI/archiso/efiboot.img \ -no-emul-boot -isohybrid-gpt-basdat \
The file /EFI/archiso/efiboot.img
is a FAT filesystem image file. If it is missing in the original ISO, then there was no UEFI support in that ISO.
The newly created ISO image arch-custom.iso
is found in the home directory. You can write the ISO image to a USB stick as explained in USB Installation Media. Alternatively you can burn the ISO image on a CD, DVD, or BD with your preferred software. On Arch, that is covered in the article about burning an ISO image.