cdstop: 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/cdstop - from package: cdtool

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