How to manipulate packages with dpkg (Enabling Muilti-Arch in Multi-Arch support) ?

$dpkg --print-architecture
amd64
$dpkg --print-foreign-architectures
$dpkg --add-architecture i386
dpkg: error: unable to create new file '/var/lib/dpkg/arch-new': Permission denied
$sudo dpkg --add-architecture i386
[sudo] password for jeffrin: 
$dpkg --print-foreign-architectures
i386
$sudo dpkg --add-architecture itest386
$dpkg --print-foreign-architectures
i386
itest386
$dpkg --remove-architecture itest386
dpkg: error: unable to create new file '/var/lib/dpkg/arch-new': Permission denied
$sudo dpkg --remove-architecture itest386
$dpkg --print-foreign-architectures
i386
$sudo dpkg --remove-architecture i386
$dpkg --print-foreign-architectures
$