How can update-manager update without the root password? [duplicate]

We need to fill in our password every time for logging in, installing new software, even for unlocking the the password manager (Is think it the only annoying thing about using Ubuntu).

But when Ubuntu ask for updates we can press "Install Updates" and everything installs without filling in a password.

Is this a bug? Or just the way how Ubuntu works?

But when ubuntu ask for updates we can press "Install Updates" and everything installs without filling in a password.

Not exactly true. It will ask for a password when something like a kernel gets updated. And try it with a non-admin user ;)

Is this a bug?

Nope.

Or just the way how ubuntu works?

Update Manager and USC do not use apt directly, they use a fork of PackageKit called aptdaemon. See: http://lists.debian.org/deity/2009/02/msg00000.html Aptdaemon already provides the following features:

• PolicyKit authorization allowing e.g. desktop user to update the cache (check for updates) passwordlessly
• Install packages from repositories or local file system, remove packages, update the cache and (safe) upgrade your system

Is think i the only annoying thing about using ubuntu

Security comes with a price. In this case a password ;)

Some additional information.

• How do I prevent PolicyKit from asking for a password?

This is the method used to make it not ask for a password.