xfdesktop: 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/bin/xfdesktop - from package: xfdesktop

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

On Debian possible default full paths are:

/usr/bin/xfdesktop - from package: xfdesktop4

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

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