slregister: 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

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/slregister - from package: sooperlooper

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