irkerhook-git: 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/irkerhook-git - from package: irker

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

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