Problem

Some Dell Presision workstations like T3600 cannot boot kernel when initrd image file is bigger than 123MB (caused by the size of DKMS modules like nvidia):

VFS: Cannot open root device: "UUID="XXX" or unknown-block(0,0): error -6

Workaround

1. Boot different kernel and check if initrd image file is too big: ll /boot/initrd.img-*
2. Edit /etc/initramfs-tools/initramfs.conf. Set MODULES=dep (instead of most) and COMPRESS=xz (instead of zstd).
3. Check new initrd image size: ll /boot/initrd.img-*.
4. Update initramfs: sudo update-initramfs -u -k X.XX.X-XX-generic (replace kernel version number)