[Dev] User ID allocation

Piotr Bartosiewicz p.bartosiewi at partner.samsung.com
Mon May 26 14:12:08 GMT 2014


On 22.05.2014 16:35, Łukasz Stelmach wrote:
> It was <2014-05-22 czw 11:16>, when Michal Witanowski wrote:
>> From: Dev [mailto:dev-bounces at lists.tizen.org] On Behalf Of Thiago Macieira
>> Sent: Wednesday, May 21, 2014 7:54 PM
>>> Em qua 21 maio 2014, às 17:35:32, Michal Witanowski escreveu:
>>>> I'm in team working on Domain Separation (Linux Containers) and we need to
>>>> reserve an UID for our daemon which will be communicating with containers
>>>> via dbus socket (it  requires that UID in host and container match, so we
>>>> can't trust default values).
>>>>
>>>> I was wondering if there exist any rules for User ID allocation on
>>>> Tizen 3.0 platform.
>>> Can't you simply have a useradd -r command in the RPM post-install
>>> rule?  This will create a UID for you. The software simply needs to
>>> getpwnam to get the UID.
> [...]
>> We can't just do "useradd -r", because it will generate a "random" User ID.
>> We must be sure that UID of the deamon user will be the same, regardless
>> system configuration, existing users in the system, etc.
> Why is that? Are you going to hardcode the uids anywhere? That is BAD.
>
Yes, we would like to hardcode the uids. Yes we know that it is BAD in 
general.

Let me explain the problem without using the 'container' word:

We have 'n' different Tizen images.
How to ensure that in every image there exists the same user='User' with
the *same* uid=<uid>.

I've already explained why the uids needs to be the same - see my earlier
mails. I can't simply do a 'useradd' on the first one and use the uid on the
other images because this uid can be occupied in some image.

-- 
Piotr Bartosiewicz
Samsung R&D Institute Poland
Samsung Electronics



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