rwhod: 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 CentOS possible default full paths are:

/usr/sbin/rwhod - from package: rwho

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/rwhod - from package: rwhod

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

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