6

/ is the highest directory in Linux. Is there a way to fake that to something else say /opt/rpmbuild/BUILDROOT?

Here's my problem space. I am trying to re-package a COTS into RPM format. The COTS came in a form of binary and I need to install that first before packaging it into RPM. The install is installing it into /opt/app directory, and I want it to install it into /opt/rpmbuild/BUILDROOT/opt/app but I couldn't force that to happen.

mailq
  • 17,023
  • 2
  • 37
  • 69
Chun Tat David Chu
  • 73
  • 3

3 Answers3

6

chroot /opt/rpmbuild/BUILDROOT can do this, but it requires that you have a working OS installed within the chroot directory.

Instead of using chroot, a simpler option would be to create a symlink from /opt/app to /opt/rpmbuild/BUILDROOT/opt/app:

mkdir -p /opt/rpmbuild/BUILDROOT/opt/app
ln -s /opt/rpmbuild/BUILDROOT/opt/app /opt/app

Then the installation will think it's working in /opt/app, but will in fact go into /opt/rpmbuild/BUILDROOT/opt/app.

Andrew Schulman
  • 8,811
  • 21
  • 32
  • 47
  • Symlinks will not work if they refer a file/folder outside the root jail. Actually they will be relative to jail's root folder. You can use hardlinks or, better, bind mounts. – Mircea Vutcovici Nov 03 '11 at 21:06
  • Thank you for your suggestion. The key is chroot but like you said you need to have a working OS installed within the chroot directory. – Chun Tat David Chu Nov 03 '11 at 21:19
  • @MirceaVutcovici: I think I wasn't clear. I meant instead of chroot, not with it. Edited to clarify. – Andrew Schulman Nov 03 '11 at 23:19
2

Have a look into man chroot, this should help you.

Sven
  • 98,649
  • 14
  • 180
  • 226
0

What you want, but you may not have asked in your question is this: a combination of chroot and overlayfs

modprobe overlay
mount -t overlay overlay -o lowerdir=/,upperdir=/home/overlay/root_fs/upper,workdir=/home/overlay/root_fs/work /home/overlay/root_fs/root_slash
cd /home/overaly/root_fs/root_slash
chroot .

I mean: you'll need 'overlay file system' kernel module and necessary userspace tools to mount it; you'll also need these three folders - one for work, one for upper where the changes will be saved and the chroot one. This way you can use as a base your O.S. with all media's mounted, shares, etc and on top write only changes to the overlay file system. The changes in your case are the 'installation files'.

Marcelo Ruggeri
  • 101
  • 4