ibnodes: 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/sbin/ibnodes - from package: infiniband-diags

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

On Debian possible default full paths are:

/usr/sbin/ibnodes - from package: infiniband-diags

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

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