arjdisp: 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/arjdisp - from package: arj

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

On Debian possible default full paths are:

/usr/bin/arjdisp - from package: arj

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

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