hexeditor: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/hexeditor - from package: ncurses-hexedit

You may install the required package with command apt-get install {package}

Error in other languages:
hexeditor: bevel nie gevind nie
hexeditor: comandă negăsită
hexeditor: comando não encontrado
hexeditor: commande introuvable
hexeditor: command not found
hexeditor: käsku ei ole
hexeditor: không tìm thấy lệnh
hexeditor: komanda nerasta
hexeditor: Kommando nicht gefunden.
hexeditor: kommandot finns inte
hexeditor: komut yok
hexeditor: nie znaleziono polecenia
hexeditor: níor aimsíodh an t-ordú
hexeditor: no se encontró la orden
hexeditor: no s'ha trobat l'ordre
hexeditor: opdracht niet gevonden
hexeditor: parancs nem található
hexeditor: perintah tidak ditemukan
hexeditor: príkaz nenájdený
hexeditor: příkaz nenalezen
hexeditor: команда не найдена
hexeditor: командата не е открита
hexeditor: 命令找不到
hexeditor: コマンドが見つかりません