xfrun4: 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/xfrun4 - from package: xfce-utils

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

On Debian possible default full paths are:

/usr/bin/xfrun4 - from package: xfce4-appfinder

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

Error in other languages:
xfrun4: bevel nie gevind nie
xfrun4: comandă negăsită
xfrun4: comando não encontrado
xfrun4: commande introuvable
xfrun4: command not found
xfrun4: käsku ei ole
xfrun4: không tìm thấy lệnh
xfrun4: komanda nerasta
xfrun4: Kommando nicht gefunden.
xfrun4: kommandot finns inte
xfrun4: komut yok
xfrun4: nie znaleziono polecenia
xfrun4: níor aimsíodh an t-ordú
xfrun4: no se encontró la orden
xfrun4: no s'ha trobat l'ordre
xfrun4: opdracht niet gevonden
xfrun4: parancs nem található
xfrun4: perintah tidak ditemukan
xfrun4: príkaz nenájdený
xfrun4: příkaz nenalezen
xfrun4: команда не найдена
xfrun4: командата не е открита
xfrun4: 命令找不到
xfrun4: コマンドが見つかりません