Re: [Bug-tar] [PATCH] add a numeric offset option for uid and gid manipulations

[Glauber Costa]

On 03/12/2013 10:17 PM, Joerg Schilling wrote:
> Paul Eggert <address@hidden> wrote:
> 
>> On 03/12/13 02:03, Glauber Costa wrote:
>>> With that, it is extremely useful when unpacking tar archives, to be
>>> able to add that offset to the end result. Specifying a user won't help,
>>> since the tar archive can have many
>>
>> Sorry, I'm not following this part.  Why can't you extract the
>> tar image in a context where the mapping is already in place?
>> If user "foo" is host user ID 4000, for example, and you're running
>> in an environment where uid 0 maps to 10000, then presumably
>> user "foo" is namespace user 14000, which is what you want, no?
> 
> Also, TAR should map by name rather then by uid in the first attempt.
> 

I am not sure what exactly you mean here. In my proposed implementation,
I documented this option to imply numeric offset. This is precisely
because only numeric UIDs matter.

If you are extracting an archive that contains a distribution image with
a particular user, there is no guarantee that such user exists in the
host system. Much less that it has an equal user id.