rwall: 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/rwall - from package: rwall

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