Sometimes I’m working on a system and I want to reboot it, but I don’t want it to go to the default boot entry. E.g. I have Arch on my desktop, but it defaults to Windows so my kids can easily start the computer.
If you are using EFI, you can reboot into a specific boot entry, just one time.
First, show the boot entries that you currently have:
sudo efibootmgr -v
Then, pick the entry you want to reboot in:
sudo efibootmgr -n 0000
Now you can reboot, and it will boot into that specific entry.