xbiso: command not found

Have You tried accessing the binary with the full path?

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/xbiso - from package: xbiso

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