xwud: 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 CentOS possible default full paths are:

/usr/bin/xwud - from package: xorg-x11-apps

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

On Debian possible default full paths are:

/usr/bin/xwud - from package: x11-apps

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