Troubleshooting Boot Problems

Boot failure ≠ reinstall. Work top-down; stop at the level that fixes it.

Step 0 — What do you actually see?

Symptom Likely layer

Nothing, no logo, fans spin

Firmware/disk order (BIOS)

GRUB rescue> prompt

GRUB config/core lost → Step 3

"AcreetionOS" menu but kernel panics / drops to emergency shell

Kernel/initramfs/fstab → Step 4

Boot loops into recovery automatically

Failover worked! Use it → Step 5

Step 1 — Firmware checks

Boot menu (F12/F11/Esc) shows your disk but not GRUB? Boot order changed (CMOS reset, Windows update). Re-select the disk; make "ubuntu"/"AcreetionOS" first in UEFI order.

Step 2 — Live ISO sanity check

Boot the ISO. If the installed system’s files look right when mounted manually, the problem is bootloader-level, not disk death.

Step 3 — Rebuild GRUB (from ISO/recovery)

Use the built-in tooling — Recovery Environment → GRUB repair automates this. Manual equivalent:

mount /dev/nvme0n1p2 /mnt && mount /dev/nvme0n1p1 /mnt/boot/efi
arch-chroot /mnt                     # or chroot per xref:chroot-rescue.adoc[]
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=AcreetionOS
grub-mkconfig -o /boot/grub/grub.cfg
exit && reboot

Step 4 — Emergency shell triage

At the emergency prompt, read the journal now, it scrolls away otherwise:

journalctl -xb -p err
systemctl --failed

Classic culprits: fstab UUID typo (mount -o remount,rw /, edit /etc/fstab, systemctl daemon-reload), full /boot blocking initramfs creation (Freeing Disk Space Safely), failed NVIDIA module build (NVIDIA Drivers on AcreetionOS).

Step 5 — Rollback options ranked

  1. Recovery Environment → Timeshift restore (fastest, covers system)

  2. Previous kernel via GRUB Advanced submenu (Kernel Management)

  3. chroot + targeted package downgrade (Chroot Rescue Guide)

Report what happened

Persistent mysteries deserve bug reports with journalctl -b -1 output attached — Reporting Bugs shows the template maintainers love.