chroot (minimalistic) best practice

There are several mount points you have to retain over chroot-ing Linux root partition, namely dev (device descriptors), proc (processes), and sys (mainly the kernel control identifiers). If you do not, silly thing happens.

So, here's mostly you have to do to chroot:
mkdir /mnt 
mount /dev/sda1 /mnt 
cd /mnt 
mount -t proc proc proc/ 
mount -t sysfs sys sys/ 
mount -o bind /dev dev/ 
chroot /mnt /bin/bash 

Having just a shell in the chroot-ed environment is sometimes a nice idea, you could just exit to return to earlier environment.