[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 

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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