After I installed Suse Linux Enterprise Desktop 10, I tried to update it. It prompted me for a root password even though the install hadn’t asked for one — it had only created a regular user. Sudo didn’t help.
I tried booting in single-user mode, but that also prompted me for the root password.
Finally, I appended
init=/bin/bash to the Linux boot command in GRUB. That booted me in a passwordless command line, letting me run
passwd and fix things.