xdg-user-dirs-update: 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/xdg-user-dirs-update - from package: xdg-user-dirs

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

On Debian possible default full paths are:

/usr/bin/xdg-user-dirs-update - from package: xdg-user-dirs

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

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