Changing only file permissions

[Hendrik Visage]

On Wed, Apr 22, 2015 at 10:17 AM, Kevin Korb <kmk at sanitarium.net> wrote:
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> No, even if bandwidth is your concern I would say that --checksum is
> wrong.  Maybe if bandwidth is so scarse that a few KB vs a few MB
> equates to dollars then sure, use --checksum.

Yes, it does for me. This is especially when I update files whose size
stays the same, and 'cause of the way transfers happened/failed, the
destination time is later/equal to the source, then I needed to have
the transfers forced, else rsync skipped over some.

>  Otherwise, letting
> rsync re-delta-xfer everything is certainly faster and not much more
> bandwidth intensive than --checksum.  Plus that is only if you screwed
> up and ran rsync wrongly in the past.  This question shouldn't matter
> as you should have synchronized mtime stamps so that rsync knows what
> is going on.
>
> In my experience, --checksum is really only useful with
> - --only-write-batch, or with --link-dest and known corruption, or with
> - --itemize-changes and a watch for hardware induced corruption.
>
> If --checksum didn't checksum absolutely everything on both ends it
> might be more useful.  But apparently the use cases for --checksum are
> so rare that nobody seems to care that --checksum is so stupid that it
> checksums files that have different file sizes (and therefore could
> only have a matching checksum if one file is a carefully crafted hash
> collision) and it even checksums file that only exist on one (or the
> other) end of the connection even though there is no file on the other
> end to compare the checksum to.  What a waste of time.
>
> On 04/22/2015 03:57 AM, Hendrik Visage wrote:
>> On Wed, Apr 22, 2015 at 9:15 AM, Kevin Korb <kmk at sanitarium.net>
>> wrote: Normally, I would say that --checksum is actually slower
>> than just letting rsync re-copy everything
>>
>>> Depends on the network capacity and costs associated with that
>>> bandwidth :(
>>
>> and therefore is almost always the wrong thing to do.
>>
>>> Nope, not when you are bandwidth and budget constraint ;)
>>
>> However, in this case, you really don't want to overwrite the
>> running OS even with files that are essentially the same.  So, if
>> the system is running from that storage then --checksum might
>> actually be useful.
>>
>> On 04/22/2015 01:59 AM, Hendrik Visage wrote:
>>>>> On Wed, Apr 22, 2015 at 1:03 AM, James Moe
>>>>> <jimoe at sohnen-moe.com> wrote: Hello, opensuse 13.2 linux
>>>>> v3.16.7-7-desktop x86_64 rsync v3.1.1
>>>>>
>>>>> I used rsync to copy /usr/ to another volume with these
>>>>> options: --recursive --one-file-system --links --stats
>>>>> --itemize-changes --quiet --delete --times After I had
>>>>> modified the system to use the new /usr volume, I realized I
>>>>> should have added: --perms --owner --group --executability
>>>>>
>>>>> So the target volume has everything set as "root root", and
>>>>> useful bits like the SetUID mode are missing.
>>>>>
>>>>> Is there a way to use rsync to restore only the
>>>>> permissions/owner/user and mode flags on the target volume
>>>>> from the source volume?
>>>>>
>>>>>> *If* their sizes and times match, then I believe rsync does
>>>>>> only the permissions/etc. changes with the -a option.
>>>>>> However, I got into the tendency when doing these type of
>>>>>> things, to use the -c/--checksum option, that way rsync
>>>>>> makes sure the files haven't changed and will
>>>>>> copy/update/etc.
>>>>>
>>>>>
>>>>>> -- Please use reply-all for most replies to avoid omitting
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>>>>>> posting, read:
>>>>>> http://www.catb.org/~esr/faqs/smart-questions.html
>>
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>
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>         Kevin Korb                      Phone:    (407) 252-6853
>         Systems Administrator           Internet:
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