ax25rtd: command not found

Have You tried accessing the binary with the full path?

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/sbin/ax25rtd - from package: ax25-apps

You may install the required package with command apt-get install {package}
Error in other languages:
ax25rtd: bevel nie gevind nie
ax25rtd: comandă negăsită
ax25rtd: comando não encontrado
ax25rtd: commande introuvable
ax25rtd: command not found
ax25rtd: käsku ei ole
ax25rtd: không tìm thấy lệnh
ax25rtd: komanda nerasta
ax25rtd: Kommando nicht gefunden.
ax25rtd: kommandot finns inte
ax25rtd: komut yok
ax25rtd: nie znaleziono polecenia
ax25rtd: níor aimsíodh an t-ordú
ax25rtd: no se encontró la orden
ax25rtd: no s'ha trobat l'ordre
ax25rtd: opdracht niet gevonden
ax25rtd: parancs nem található
ax25rtd: perintah tidak ditemukan
ax25rtd: príkaz nenájdený
ax25rtd: příkaz nenalezen
ax25rtd: команда не найдена
ax25rtd: командата не е открита
ax25rtd: 命令找不到
ax25rtd: コマンドが見つかりません