ghkl: 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/ghkl - from package: ghkl
/usr/lib/debug/usr/bin/ghkl - from package: libhkl-dbg

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