ibsim: 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 CentOS possible default full paths are:

/usr/bin/ibsim - from package: ibsim

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/ibsim - from package: ibsim-utils

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

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