System Recovery

How to re-build initramfs after an mkinitcpio configuration error resulted in a broken boot?

Approach

• unlock crypto root disk and bring system up inside systemd-nspawn container, then re-build

• use only systemd-nspawn: non-systemd containers, such as chroot are not supported

Assumptions

• system has luks root, for example:

   /dev/sda1 -> /boot
   /dev/sda2 -> [swap]
   /dev/sda3 -> [luks root]

• system can boot form archiso usb disk

Recovery Steps

• boot into archiso usb disk as host

• review soon-to-be-container disk layout

lsblk

NAME     MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda        8:0    0 232.9G  0 disk  
├─sda1     8:1    0   499M  0 part  
├─sda2     8:2    0   4.9G  0 part  
└─sda3     8:3    0 227.5G  0 part  

• unlock root partition form archiso host

cryptsetup luksOpen /dev/sda3 root

• prepare boot and root mounts for the container

mkdir -p /mnt/{boot,root}
mount /dev/sda1 /mnt/boot
mount /dev/mapper/root /mnt/root

• launch and enter system-to-recover inside the machine container

systemd-nspawn --boot --bind=/mnt/boot:/boot --directory=/mnt/root

mkinitcpio Rebuild Steps

• read the manual
• study the units
• and try again