Arch Linux - pacman -Syu failed - cannot issue any commands

Question

I was running a full system update. Said update failed abruptly, with the last package modified seemingly being the removal of glibc. Now, nothing works. System built-ins such as cd still work, but on issuance of any other command, an error of the following form results:

bash: /usr/bin/COMMAND: No such file or directory

With some commands causing this error instead:

bash: /usr/bin/COMMAND: /bin/bash: bad interpreter: No such file or directory

I do not know how to proceed. I am scared to shut my computer down or to log out or to close my open terminals. I am using i3 and all keybindings for switching workspaces and the like still function normally, save for my bindings to open a new terminal or the like.

Is there a way for me to undo this package removal? Is that what caused this issue?

Answer 1

This is documented on the pacman page of the wiki:

In the case that pacman crashes with a "database write" error while removing packages, and reinstalling or upgrading packages fails thereafter, do the following:

1. Boot using the Arch installation media. Preferably use a recent media so that the pacman version matches/is newer than the system.
2. Mount the system's root filesystem, e.g. mount /dev/sdaX /mnt as root, and check the mount has sufficient space with df -h
3. Mount the proc, sys and dev filesystems as well: mount -t proc proc /mnt/proc; mount --rbind /sys /mnt/sys; mount --rbind /dev /mnt/dev
4. If the system uses default database and directory locations, you can now update the system's pacman database and upgrade it via pacman --sysroot /mnt -Syyu as root.
5. After the upgrade, one way to double-check for not upgraded but still broken packages: find /mnt/usr/lib -size 0
6. Followed by a re-install of any still broken package via pacman --sysroot /mnt -S package.