Booting with systemd-boot hangs on black screen with white caret

TL;DR: a black screen with a blank caret with systemd-boot is a symptom of a malformed mkinitcpio.conf file, resulting in an incomplete initramfs image.

I was updating my /etc/mkinitcpio.conf to enable resume from hibernation, when I noticed there was a .pacnew version of the config file beside it. I went ahead and hand-edited the new changes, added resume to the list of HOOKS, closed the file and ran mkinitcpio -p linux.

Things seemed nice and dandy until I updated my kernel again. After a reboot, directly after UEFI POST sequence, I was dumped to a black screen with a single white caret, hanging indefinitely. No keyboard combinations worked, and even waiting two hours did nothing.

I booted the system up again with the Arch Linux installation medium and mounted my main disk. I then ran a diff of the two mkinitcpio.conf versions to try and find the errors. It appeared that in both my MODULES and my HOOKS section, I had surrounded the items in both parentheses and a single pair of double quotes.

MODULES=("intel_agp i915")
HOOKS=("base udev keyboard keymap consolefont autodetect modconf block efiverify encrypt lvm2 resume decryption-keys filesystems fsck")

The main upstream package change of the mkinitcpio.conf file was to switch from a single set of double quotes to signify lists, into using bash array notation.

# Old format
list="a b c d e f g"

# New format (bash array notation)
list=(a b c d e f g)

# What I did wrong in my mkinitcpio.conf file
list=("a b c d e f g")

The last example resulted in the list variable containing an array with a single item, hence early boot process unable to load required modules and run initial hooks.

I suspect I must’ve missed some warnings from pacman hooks after the system upgrade when it generated the new initramfs images.

But the conclusion is that a black screen with a blank caret with systemd-boot is a symptom of a malformed mkinitcpio.conf file, resulting in an incomplete initramfs image.

References

• man mkinitcpio.conf