Corey Wright wrote:
I've been struggling to fully understand how vhashify works for a while
now. I want to know more about it. It would be nice if someone could
answer the following questions for me or point to some document which
can help me understand the vhashify and unify better:
isn't there a vhashify.c? ;-)
I had a look at that but specifically for the answer of the first
questions, unfortunately I didn't quite grasp what was going on :)
The reason I asked the questions is that I have 2 identical vservers
(i.e. all the files are the same except those created by the skeleton
build method). However, when I hashify, one vserver ends up with a lot
more unified files than the other. So I'm trying to figure out why this
is happening...I have not customized the exclude list in either vserver.
1) What files and how does vhashify step through and compare for
unification?
dunno. i've wondered that myself, and postulated some, but "the proof is
in the pudding" so i haven't questioned it too much.
i'm guessing here, but every file in /etc/vservers/<vserver>/vdir not
explicitly excluded by some pattern in
/etc/vservers/<vserver>/apps/vunify/exclude or
/usr/lib/util-vserver/defaults/vunify-exclude is hashed, looked up in a
hash table (ie files within /etc/vservers/.defaults/apps/vunify/hash/0
named after value of hash of contents), file attributes are compared
against the hardlink in the hash table, and if found equal, then the files
are "unified".
so how close did i get? :-D
herbert, daniel, somebody correct me if i'm wrong.
2) What things are compared to determine if the files can be unified? In
other words, what properties of the file should be the same?
all properties besides file name. at least that's my guess according to
http://www.debian.org/doc/manuals/debian-tutorial/ch-advanced.html#s-advanced-files-hardlinks
as unification just takes advantage of hardlinks (with the special
property of being immutable but unlinkable).
3) What is the format of an exclude file?
from http://linux-vserver.org/alpha+util-vserver, under "Directory/vserver
unification":
It has rsync-like excludelists, so that you can e.g. exclude anything
under /etc/ except /etc/termcap; the corresponding excludelist would be
+/etc/termcap
/etc
further see http://samba.anu.edu.au/ftp/rsync/rsync.html, specifically the
FILTER RULES and INCLUDE/EXCLUDE PATTERN RULES sections.
take all the above with a grain of salt as i'm just making educated
guesses. hopefully somebody will at least confirm whether i'm right or
wrong.
corey
Thanks for your help. I really appreciate it.
-FS
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