xs: 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/xs - from package: xs

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

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