Ubuntu Linux Essentials: Booting Into Single User Mode And Protecting Against Unauthorized Access
Veeam News, Thursday, May 4,2023
Anyone with console access to a Linux machine can get root access on the machine by booting into 'single user mode'. In this blog, I will show how to boot into single user mode and how to protect the bootloader against unauthenticated attempts to boot into single user mode.
Usually, single user mode is used when someone forgot the administrative credentials for a Linux system or troubleshooting. Another reason could be that someone locked down a Linux system in a way as described in the 'Installing Ubuntu Linux for Veeam Hardened Repository'. In that case, there is intentionally no active root account configured and the only user on the system has no (or very limited) sudo permissions.