dhex: command not found

Have You tried accessing the binary with the full path?

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/dhex - from package: dhex

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