mcx: 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/mcx - from package: mcl

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

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