nwall: 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/nwall - from package: nwall

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

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