gnuserv: 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/bin/gnuserv - from package: gnuserv

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