Re: [vserver] Copy-on-write Hard Links, Shared Libraries, Prelink and Memory

From: Herbert Poetzl <herbert_at_13thfloor.at>
Date: Thu 10 Jun 2010 - 01:53:24 BST
Message-ID: <20100610005324.GF3270@MAIL.13thfloor.at>

On Wed, Jun 09, 2010 at 06:08:27PM +0200, Eugen Leitl wrote:
> On Wed, Jun 09, 2010 at 05:01:12PM +0100, Gordan Bobic wrote:
> > >Can you cut& paste the exact rm command you use?

> > He did. The find command execs 'rm -f' on all the files it finds that
> > have a hard link count of 1. Or am I misunderstanding your question?

> Oh, so
> find /var/lib/vservers/.hash -type f -links 1 -exec rm -v '{}' ';'

> does it for Debian, then. I thought I was missing something.
> Below did strike as a bit much space for 253 barebone guests.

> beryllium:~# df -k
> Filesystem 1K-blocks Used Available Use% Mounted on
> /dev/sda1 73742752 42989868 27006932 62% /

this shows me that you do not favor a good design, as
putting _everything_ on one partition (including the
guests, which might need/want filesystem tagging sooner
or later) ...

> tmpfs 2031656 0 2031656 0% /lib/init/rw
> udev 10240 692 9548 7% /dev
> tmpfs 2031656 0 2031656 0% /dev/shm

> Is there a way to verify the symlinks are actually there?

there are no symlinks, unification uses hard links ...

> I don't see them in the filesystem explicitly.

hard links are indistinguishable from the original file
even more, there is no 'original' as each directory
entry pointing to an inode is a file, regardless if it
is sharing the content (data) with another entry

> Does the kernel hide it?

nope, you can see them via the link count ....

best,
Herbert

> --
> Eugen* Leitl leitl http://leitl.org
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Received on Thu Jun 10 01:54:00 2010

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