Subject: Re: [vserver] Copy-on-write Hard Links, Shared Libraries, Prelink and Memory
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Thu, 10 Jun 2010 02:53:24 +0200

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 <a href="leitlhttp://leitl.org">leitl</a> http://leitl.org
> ______________________________________________________________
> ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org
> 8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE