cantor_rserver: 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/cantor_rserver - from package: cantor-backend-r

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

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