liveimage-mount: 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/liveimage-mount - from package: livecd-tools

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

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