xa: 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/xa - from package: xa

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

On Debian possible default full paths are:

/usr/bin/xa - from package: xa65

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

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