I installed MX Linux on an HP laptop using a bootable USB. It starts with the USB plugged in, but without it I get a Boot Device Not Found error. Changing the boot order and enabling Legacy boot didn't help.
I'm new to Linux and think the bootloader might be on the USB. How can I check and fix it?
First check where MX Linux actually ended up. Boot with the USB connected, open a terminal and run lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINTS. Look for the roughly 500 GB internal drive and the smaller USB drive. The mountpoint / shows which device contains the system you're currently running.
Please share the output before trying bootloader repair. The USB could be starting an installation on the hard drive, or it could be starting the live system from the USB. Those need different fixes.
The boot mode matters here. A system installed in UEFI mode won't necessarily boot with Legacy mode enabled, and the reverse can also be true. From the running system, check whether /sys/firmware/efi exists. If it does, that session booted in UEFI mode.
Once you know where the installed system is and which mode it uses, MX Linux has boot repair tools that may be able to reinstall GRUB to the internal drive. Don't pick a drive or run GRUB installation commands until those details are clear. A wrong choice could change the USB or another disk instead.
3u~sprocketcase_619:
If you're booted into the live USB, that check tells you the live session's mode, not necessarily the mode used for the hard drive installation.
If the hard drive doesn't actually contain the installation, reinstalling may be the simplest route. Boot the installer, identify the internal drive by its size, and double-check both the installation destination and bootloader settings before confirming.
Using the entire disk erases its contents, so only do this after checking that there's nothing on that drive you need to keep. If the installation is already there, diagnose the boot setup first rather than wiping it again.
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Vornik.9d:
You can also run sudo fdisk -l for a fuller partition listing. Check the drive sizes carefully rather than assuming a particular device name belongs to the hard drive.