icinga: 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/sbin/icinga - from package: icinga-core
/usr/lib/debug/usr/sbin/icinga - from package: icinga-dbg

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

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