nrsdrv: 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/nrsdrv - from package: ax25-tools

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