exrheader: 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/exrheader - from package: OpenEXR

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

On Debian possible default full paths are:

/usr/bin/exrheader - from package: OpenEXR

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

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