exrmakepreview: 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/exrmakepreview - from package: OpenEXR

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

On Debian possible default full paths are:

/usr/bin/exrmakepreview - from package: OpenEXR

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

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