After doing a Ubuntu update, I found my droplet unbootable. Digital Ocean provides a useful utility ISO for restarting a droplet in recovery mode, but by itself I wasn’t able to see or fix the problem. Luckily I found a blog post with the correct set of remounts and chrooting to be able to rerun apt and get everything running.

In order to get things running, you restart the droplet with the Recovery ISO as the startup drive, mount the main disk, choose 6 for interactive shell, then in the shell:

mount --bind /dev /mnt/dev
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
mount --bind /run /mnt/run"      
chroot /mnt
apt update
apt upgrade

Restart the droplet and boot from main harddisk (you have to power cycle, a soft reboot doesn’t do the trick). After rebooting, I reran the updates just to make sure:

apt update
apt upgrade
apt autoremove

I found that not all my docker containers would come back up, and traced the failure to insufficient peak memory. This lead me to move my swap to a larger swapfile to allow for greater headroom.

fallocate -l 3G /swapfile3g
ls -lh /swapfile
ls -lh /swapfile3g
chmod 600 /swapfile3g
mkswap /swapfile3g
swapon /swapfile3g
swapon -s
vi /etc/fstab
swapoff /swapfile