virt-clone: 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/virt-clone - from package: python-virtinst

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

On Debian possible default full paths are:

/usr/bin/virt-clone - from package: virtinst

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

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