ibv_devices: 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/ibv_devices - from package: libibverbs-utils

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

On Debian possible default full paths are:

/usr/bin/ibv_devices - from package: ibverbs-utils

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

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