virtualenv-clone: 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/virtualenv-clone - from package: python-virtualenv-clone

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

On Debian possible default full paths are:

/usr/bin/virtualenv-clone - from package: virtualenv-clone

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