exrdisplay: 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 Debian possible default full paths are:

/usr/bin/exrdisplay - from package: openexr-viewers

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

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