opj2dat: 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/opj2dat - from package: liborigin

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

On Debian possible default full paths are:

/usr/bin/opj2dat - from package: opj2dat

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

Error in other languages:
opj2dat: bevel nie gevind nie
opj2dat: comandă negăsită
opj2dat: comando não encontrado
opj2dat: commande introuvable
opj2dat: command not found
opj2dat: käsku ei ole
opj2dat: không tìm thấy lệnh
opj2dat: komanda nerasta
opj2dat: Kommando nicht gefunden.
opj2dat: kommandot finns inte
opj2dat: komut yok
opj2dat: nie znaleziono polecenia
opj2dat: níor aimsíodh an t-ordú
opj2dat: no se encontró la orden
opj2dat: no s'ha trobat l'ordre
opj2dat: opdracht niet gevonden
opj2dat: parancs nem található
opj2dat: perintah tidak ditemukan
opj2dat: príkaz nenájdený
opj2dat: příkaz nenalezen
opj2dat: команда не найдена
opj2dat: командата не е открита
opj2dat: 命令找不到
opj2dat: コマンドが見つかりません