Re: [CFT] rewrite of the merge(1) utility

On Friday, August 14, 2015 10:31:46 PM Slawa Olhovchenkov wrote:
> On Fri, Aug 14, 2015 at 10:52:04AM -0700, John Baldwin wrote:
> 
> > On Friday, August 14, 2015 10:39:51 AM Slawa Olhovchenkov wrote:
> > > On Fri, Aug 14, 2015 at 12:14:28AM +0300, Slawa Olhovchenkov wrote:
> > > 
> > > > On Thu, Aug 13, 2015 at 08:23:02AM -0700, John Baldwin wrote:
> > > > 
> > > > > On Thursday, August 13, 2015 04:13:43 PM Slawa Olhovchenkov wrote:
> > > > > > On Tue, Aug 04, 2015 at 10:00:06PM -0700, John Baldwin wrote:
> > > > > > 
> > > > > > > On Sunday, July 26, 2015 03:26:22 AM Baptiste Daroussin wrote:
> > > > > > > > Hi all,
> > > > > > > > 
> > > > > > > > I was botherd to not have the merge(1) utility available in base (for etcupdate)
> > > > > > > > when building base WITHOUT_RCS.
> > > > > > > > 
> > > > > > > > So I have rewritten a merge(1) utility which should be compatible.
> > > > > > > > 
> > > > > > > > I used the 3-way merge code from the fossil VCS instead of making it call diff3.
> > > > > > > > All I have done from the fossil code is adapting it to use sbuf(9).
> > > > > > > > 
> > > > > > > > The bonus for end users is the merge from fossil can resolve situation where the
> > > > > > > > diff3 in base cannot. (which explains a "failure" with the GNU RCS test suite)
> > > > > > > > 
> > > > > > > > meaning etcupdate will be more happy merge configuration files.
> > > > > > > 
> > > > > > > Thanks!  This will save me from having to hack etcupdate to use diff3 instead
> > > > > > > of merge.
> > > > > > 
> > > > > > Hi, can I use etcupdate to update /etc w/o source tree?
> > > > > > I.e. I take from new distro /var/db/etcupdate and try to update /etc?
> > > > > 
> > > > > etcupdate does a 3-way merge of an "old" stock /etc and a "new" stock /etc
> > > > > into /etc.  The "old" stock /etc is always stored in /var/db/etcupdate.
> > > > > The "new" stock /etc has to come from somewhere.  One option is to generate
> > > > > it from /usr/src (e.g. after a buildworld).  However, you can also pregenerate
> > > > > tarballs from a /usr/src tree on one machine and then use those tarballs
> > > > > instead of generating an /etc tree from /usr/src on another machine.  I've
> > > > > used this for upgrades of a cluster of machines where a single machine would
> > > > > build release "images" that were basically a buildworld + an 'etcupdate build'
> > > > > from the corresponding src tree.  I then used 'etcupdate -t /path/to/tarball'
> > > > > to update /etc after installing the new world.
> > > > > 
> > > > > The idea is that for something like freebsd-update one could ship the latest
> > > > > etcupdate build tarball on each update to do a full 3-way merge of /etc.
> > > > 
> > > > What about /var/db/etcupdate from install media?
> > > > Can I use this?
> > > > What best way for work with /var/db/etcupdate from install media
> > > > (storing, saving and etc)?
> > > 
> > > As I see, /var/db/etcupdate/current match installed version.
> > > Is this enough?
> > > How I use this?
> > 
> > There are a few ways.  Newer installs do bootstrap it for you, so if you
> > follow the traditional source upgrade method you can just run 'etcupdate'
> > in place of 'mergemaster'.  If you do not want to have a /usr/src tree,
> > how are you updating your world?
> 
> yes, I don't want to have /usr/src tree.
> I have buld host and run release.sh.
> After done I use R/ftp/*.txz for extract on target host.
> I see var/db/etcupdate/current in base.txz.
> But I don't cleanly understund etcupdate:
>  - is this enough (var/db/etcupdate/current from base.txz)?
>  - what is best way to preserve var/db/etcupdate/current before
>    extract?
>  - do I need some work for record changes in /etc?

In this model, I think etcupdate isn't really what you need/want.
For one, if you extract base.txz it already overwrites your files
in /etc and loses any local changes (including any files that
etcupdate would upgrade).  It doesn't lose new files like /etc/fstab
or /etc/rc.conf, but if you make changes to existing files (like
/etc/ttys) then extracting base.txz will overwrite those with the
stock versions.  If you wanted to not overwrite /etc then you could
use etcupdate to merge in the changes to /etc instead.  However,
you would need to do something like this:

1) Ignore /etc and /var/db/etcupdate/current when you extract
   base.txz via --exclude.

2) Extract just /var/db/etcupdate/current from base.txz to
   some other temporary location (/some/tmp/path).

3) Create a new tarball from that tree
   ( tar cfy foo.tbz -C /some/tmp/path/var/db/etcupdate/current . )

4) Use foo.tbz with etcupdate as the tarball (etcupdate -t foo.tbz)

Alternatively, you could save on steps 2 + 3 by patching your release
process to run 'etcupdate build' (you can see where the current release
Makefile runs 'etcupdate extract' and use 'build' with the same options).

-- 
John Baldwin