irk: 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/irk - from package: irker

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

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