nchexedit (ncurses-based hex editor)

NCurses Hexedit is a full screen text mode Hex editor using the curses
library.

nchexedit lets you edit any file as its byte-for-byte representation. It
can even let you view and edit your fixed disks on your Linux system.

The original name for nchexedit is "hexedit", but there's already a
hexedit on SBo (a completely different program, though it's also a hex
editor). nchexedit can be installed without conflicting with hexedit.

On Debian and related systems, the package for this is called
"ncurses-hexedit", and the binary itself is called "hexeditor".