s9help: 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/s9help - from package: scheme9

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

Error in other languages:
s9help: bevel nie gevind nie
s9help: comandă negăsită
s9help: comando não encontrado
s9help: commande introuvable
s9help: command not found
s9help: käsku ei ole
s9help: không tìm thấy lệnh
s9help: komanda nerasta
s9help: Kommando nicht gefunden.
s9help: kommandot finns inte
s9help: komut yok
s9help: nie znaleziono polecenia
s9help: níor aimsíodh an t-ordú
s9help: no se encontró la orden
s9help: no s'ha trobat l'ordre
s9help: opdracht niet gevonden
s9help: parancs nem található
s9help: perintah tidak ditemukan
s9help: príkaz nenájdený
s9help: příkaz nenalezen
s9help: команда не найдена
s9help: командата не е открита
s9help: 命令找不到
s9help: コマンドが見つかりません