xetex: 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/xetex - from package: texlive-xetex

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

On Debian possible default full paths are:

/usr/bin/xetex - from package: texlive-binaries

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

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