livecd-iso-to-pxeboot: 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

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/livecd-iso-to-pxeboot - from package: livecd-tools

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