iv: 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/iv - from package: OpenImageIO-iv

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

On Debian possible default full paths are:

/usr/bin/iv - from package: openimageio-tools

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

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