opj_dec_server: 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/opj_dec_server - from package: libopenjpip-dec-server
/usr/bin/opj_dec_server - from package: openjpip-dec-server

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

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