In order for certain programs to function properly, the proc file system must be available within the chroot environment. As a file system can be mounted as many times and in as many places as you like, it's not a problem that the proc file system is already mounted on your host system -- especially so because proc is a virtual file system.
The proc file system is mounted under /proc by running the following command:
mount proc /proc -t proc |
You will most likely get some warning messages from the mount command, such as these:
Ignore these, they're just due to the fact that the system isn't installed completely yet and some files are missing. The mount itself will be successful and that's all we care about at this point.