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isomorphismes
Asked: 2012-06-25 17:54:05 +0800 CST

How to use `chown` and `chmod` to make a "pipe" or "pass through" link from guest directory to elsewhere

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I want to either extend the size of my guest partition or figure out how to copy stuff from the guest partition to my normal /home directory.

(Because of some other problems I can only run Xorg as guest, but I can log into virtual console as myself or root.)

Here's the motivation: I want to torrent a large file. It's larger than my guest filesystem. But I have plenty of space on my real drive, I just can't log into it graphically.

So I tried to set up a "pipe" to get the file out of the tmpfs. I did:

su -u myself 
#catch
mkdir ~/receiver_dir

sudo su
cd /tmp/guest-lkj567UIO/ 
#throw
ln -s mario_pipe /home/myself/receiver_dir
chown -R guest-lkj567UIO /home/myself/receiver_dir
chown -R guest-lkj567UIO /tmp/guest-lkj567UIO/mario_pipe
chmod -R a+rw /home/myself/receiver_dir
chmod -R a+rw /tmp/guest-lkj567UIO/mario_pipe

su -u guest-lkj567UIO
cd /tmp/guest-lkj567UIO
cd mario_pipe
touch something #success!

However, when I try to torrent to /tmp/guest-lkj567UIO/mario_pipe, Transmission says I don't have write permissions. But it looks like I just wrote there? And that everybody (a+rw) can write there in fact?

Maybe this indicates I don't actually understand chown and chmod but nothing from their man pages pops out.

12.04

1 Answers

  1. Best Answer

    When you log in as guest, there is an apparmor profile that is loaded to restrict access to lock down the guest account so that it can't write outside of its home directory, even if the file's permissions give access.

    You might be able to get around this by using a bind mount instead of a symlink:

    mkdir /tmp/guest-lkj567UIO/mario_pipe
mount --bind /home/myself/receiver_dir /tmp/guest-lkj567UIO/mario_pipe
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