decode_aprs: 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/decode_aprs - from package: direwolf

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

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