Sometimes it might be necessary to start in single-user mode to do some administration work, or even reset an existing password. Normally this can be achieved via the GRUB boot loader. CentOS / RedHat (with root account enabled) Switch on your system. Press Esc until the GRUB menu shows up.…
Ubuntu/GRUB: Error: invalid environment block
After a recent system update I got the following error message: Luckily the system would boot up but ignoring errors isn’t best practice. This error is caused by a faulty GRUB2 environment block. This is a file located in /boot/grub/grubenv. You can easily regenerate it with the following commands. It…
Ubuntu: Fixing the “error: no video mode activated” message on boot
During boot of your system and just after the BIOS messages Ubuntu might display a black screen with an error: no video mode activated message. The system boots normally but it is annoying. GRUB by default hides the boot menu and this message can show up if there is no…
