Linux – How to Mount dev, proc, sys in a chroot Environment

chrootdebianlinux

I'm trying to create a Linux image with custom picked packages.
What I'm trying to do is to hand craft the packages I'm going to use on an XO laptop, because compiling packages takes really long time on the real XO hardware, if I can build all the packages I need and just flash the image to the XO, I can save time and space.

When I tried to install some packages, it failed to configure due to missing the proc, sys, dev directories. So, I learned from other places that I need to "mount" the host proc, … directories to my chroot environment.

I saw two syntax and am not sure which one to use.

In host machine:

  mount --bind /proc <chroot dir>/proc

and another syntax (in chroot environment):

  mount -t proc none /proc

Which one should I use, and what are the difference?

Best Answer

For /proc and /sys, I suppose you could use either method. They are both special file systems so they can be recreated any number of times (the bind mount method uses the exact same mount as the host system, whereas the other method uses a new mount). I've always seen the bind mount recommended in guides, so I'd use that. As far as I know, there is no real important difference.

However, /dev is usually a tmpfs mount that is managed by udev, so it has to be the actual same file system as on the host machine. That means that you would need to use the bind mount method.

If this chroot is going to be around for awhile, you can put these entries in /etc/fstab on the host system to simplify things.

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