JD | 16 Apr 00:42 2011
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Finishing rebuild of rpms, from deltarpms

Doing yum update cause yum to issue
this message
Finishing rebuild of rpms, from deltarpms

What is the significance of this, and why is
it being done?
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Joe Zeff | 16 Apr 01:44 2011
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Re: Finishing rebuild of rpms, from deltarpms

On 04/15/2011 03:42 PM, JD wrote:
> Doing yum update cause yum to issue
> this message
> Finishing rebuild of rpms, from deltarpms
>
> What is the significance of this, and why is
> it being done?

Presumably, you have the presto plugin installed and active.  This means 
that instead of downloading the complete rpm for each update, yum just 
downloads the deltarpm, which only contains the changes from the last 
version, then applies the changes to the cached copies of the rpms, 
changing them to the latest version before updating.  As most of the 
updated rpm is the same as the older version, this drops the amount of 
data downloaded by anywhere from 70-90%, sometimes more.  Of course, 
people on unlimited data plans may not worry about the extra bandwidth, 
but very often the time taken to rebuild the rpms is less than the time 
needed to download the complete new version.

If the above doesn't quite make sense, don't worry; yum is just telling 
you that it's just finished saving you some (possibly valuable) bandwidth.
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JD | 16 Apr 03:49 2011
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Re: Finishing rebuild of rpms, from deltarpms

On 04/15/2011 04:44 PM, Joe Zeff wrote:
> On 04/15/2011 03:42 PM, JD wrote:
>> Doing yum update cause yum to issue
>> this message
>> Finishing rebuild of rpms, from deltarpms
>>
>> What is the significance of this, and why is
>> it being done?
> Presumably, you have the presto plugin installed and active.  This means
> that instead of downloading the complete rpm for each update, yum just
> downloads the deltarpm, which only contains the changes from the last
> version, then applies the changes to the cached copies of the rpms,
> changing them to the latest version before updating.  As most of the
> updated rpm is the same as the older version, this drops the amount of
> data downloaded by anywhere from 70-90%, sometimes more.  Of course,
> people on unlimited data plans may not worry about the extra bandwidth,
> but very often the time taken to rebuild the rpms is less than the time
> needed to download the complete new version.
>
> If the above doesn't quite make sense, don't worry; yum is just telling
> you that it's just finished saving you some (possibly valuable) bandwidth.
Sure it makes sense! So, only the items (files)
of the rpm that changed get downloaded (my guess)??
That's not too bad. What would be better is
getting a program to do a binary diff between
old rpm and new rpm, producing a binary
patch file, and applying the binary patch
file on the user's old cache of the rpm and installing
that.  See http://www.daemonology.net/bsdiff/
and of course, bsdiff and bspatch are in the fedora repo
(Continue reading)

Andre Robatino | 16 Apr 06:04 2011

Finishing rebuild of rpms, from deltarpms

http://cedarandthistle.wordpress.com/2009/11/06/on-binary-delta-algorithms/

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JD | 16 Apr 07:33 2011
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Re: Finishing rebuild of rpms, from deltarpms

On 04/15/2011 09:04 PM, Andre Robatino wrote:
> http://cedarandthistle.wordpress.com/2009/11/06/on-binary-delta-algorithms/
Read the article and parts of the thesis.
So, the final version of the algorithm
still remains with the University of Oxford??

I downloaded the bsdiff  srpm for fc15 and built it.

I then used it to diff
-rwxr-xr-x  1 root root 3699072 Feb  6 23:09 
/boot/vmlinuz-2.6.35.11-83.fc14.i686
vs
-rwxr-xr-x  1 root root 3702144 Mar 31 15:26 
/boot/vmlinuz-2.6.35.12-88.fc14.i686
and the resulting patch
-rw-r--r-- 1    root root 3554921 Apr 15 22:17 
vmlinux-2.6.35.11-83--2.6.35.12-88.patch

So, you can see that the patch is almost the same size as the files diffed.

Obviously, version 4.3-8 does not contain the unpublished optimizations
that Colin Percival mentions in his thesis.

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(Continue reading)

Jonathan Dieter | 16 Apr 07:58 2011

Re: Finishing rebuild of rpms, from deltarpms

On Fri, 2011-04-15 at 22:33 -0700, JD wrote:
> On 04/15/2011 09:04 PM, Andre Robatino wrote:
> > http://cedarandthistle.wordpress.com/2009/11/06/on-binary-delta-algorithms/
> Read the article and parts of the thesis.
> So, the final version of the algorithm
> still remains with the University of Oxford??
> 
> I downloaded the bsdiff  srpm for fc15 and built it.
> 
> I then used it to diff
> -rwxr-xr-x  1 root root 3699072 Feb  6 23:09 
> /boot/vmlinuz-2.6.35.11-83.fc14.i686
> vs
> -rwxr-xr-x  1 root root 3702144 Mar 31 15:26 
> /boot/vmlinuz-2.6.35.12-88.fc14.i686
> and the resulting patch
> -rw-r--r-- 1    root root 3554921 Apr 15 22:17 
> vmlinux-2.6.35.11-83--2.6.35.12-88.patch
> 
> So, you can see that the patch is almost the same size as the files diffed.
> 
> Obviously, version 4.3-8 does not contain the unpublished optimizations
> that Colin Percival mentions in his thesis.

A couple of things:

     1. vmlinuz is compressed and it's essentially useless to delta
        compressed files without uncompressing them first.
     2. We use the program deltarpm to make deltas between rpms.
        Deltarpm uses a modified bsdiff algorithm as well as the add
(Continue reading)

JD | 16 Apr 08:06 2011
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Re: Finishing rebuild of rpms, from deltarpms

On 04/15/2011 10:58 PM, Jonathan Dieter wrote:
> On Fri, 2011-04-15 at 22:33 -0700, JD wrote:
>> On 04/15/2011 09:04 PM, Andre Robatino wrote:
>>> http://cedarandthistle.wordpress.com/2009/11/06/on-binary-delta-algorithms/
>> Read the article and parts of the thesis.
>> So, the final version of the algorithm
>> still remains with the University of Oxford??
>>
>> I downloaded the bsdiff  srpm for fc15 and built it.
>>
>> I then used it to diff
>> -rwxr-xr-x  1 root root 3699072 Feb  6 23:09
>> /boot/vmlinuz-2.6.35.11-83.fc14.i686
>> vs
>> -rwxr-xr-x  1 root root 3702144 Mar 31 15:26
>> /boot/vmlinuz-2.6.35.12-88.fc14.i686
>> and the resulting patch
>> -rw-r--r-- 1    root root 3554921 Apr 15 22:17
>> vmlinux-2.6.35.11-83--2.6.35.12-88.patch
>>
>> So, you can see that the patch is almost the same size as the files diffed.
>>
>> Obviously, version 4.3-8 does not contain the unpublished optimizations
>> that Colin Percival mentions in his thesis.
> A couple of things:
>
>       1. vmlinuz is compressed and it's essentially useless to delta
>          compressed files without uncompressing them first.
>       2. We use the program deltarpm to make deltas between rpms.
>          Deltarpm uses a modified bsdiff algorithm as well as the add
(Continue reading)

Jonathan Dieter | 16 Apr 08:19 2011

Re: Finishing rebuild of rpms, from deltarpms

On Fri, 2011-04-15 at 23:06 -0700, JD wrote:
> On 04/15/2011 10:58 PM, Jonathan Dieter wrote:
> > On Fri, 2011-04-15 at 22:33 -0700, JD wrote:
> >> On 04/15/2011 09:04 PM, Andre Robatino wrote:
> >>> http://cedarandthistle.wordpress.com/2009/11/06/on-binary-delta-algorithms/
> >> Read the article and parts of the thesis.
> >> So, the final version of the algorithm
> >> still remains with the University of Oxford??
> >>
> >> I downloaded the bsdiff  srpm for fc15 and built it.
> >>
> >> I then used it to diff
> >> -rwxr-xr-x  1 root root 3699072 Feb  6 23:09
> >> /boot/vmlinuz-2.6.35.11-83.fc14.i686
> >> vs
> >> -rwxr-xr-x  1 root root 3702144 Mar 31 15:26
> >> /boot/vmlinuz-2.6.35.12-88.fc14.i686
> >> and the resulting patch
> >> -rw-r--r-- 1    root root 3554921 Apr 15 22:17
> >> vmlinux-2.6.35.11-83--2.6.35.12-88.patch
> >>
> >> So, you can see that the patch is almost the same size as the files diffed.
> >>
> >> Obviously, version 4.3-8 does not contain the unpublished optimizations
> >> that Colin Percival mentions in his thesis.
> > A couple of things:
> >
> >       1. vmlinuz is compressed and it's essentially useless to delta
> >          compressed files without uncompressing them first.
> >       2. We use the program deltarpm to make deltas between rpms.
(Continue reading)

Joe Zeff | 16 Apr 12:09 2011
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Re: Finishing rebuild of rpms, from deltarpms

On 04/15/2011 06:49 PM, JD wrote:
>   What would be better is
> getting a program to do a binary diff between
> old rpm and new rpm, producing a binary
> patch file, and applying the binary patch
> file on the user's old cache of the rpm and installing
> that.

That's exactly what a deltarpm is.  How many files do you think there 
are to be changed when you download a new kernel, for example.
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Gmane