irsim: 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/irsim - from package: irsim

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

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