Retrieving non-/etc/passwd users with Python 3?

Loris Bennett

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Mar 31, 2021, 8:16:02 AM3/31/21

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Hi,

I want to get a list of users on a Linux system using Python 3.6. All
the users I am interested in are just available via LDAP and are not in
/etc/passwd. Thus, in a bash shell I can use 'getent' to display them.

When I try to install the PyPi package

getent

I get the error

File "/tmp/pip-build-vu4lziex/getent/setup.py", line 9, in <module>
long_description = file('README.rst').read(),
NameError: name 'file' is not defined

I duckduckwent a bit and the problem seems to be that 'file' from Python
2 has been replaced by 'open' in Python 3.

So what's the standard way of getting a list of users in this case?

Cheers,

Loris

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Chris Angelico

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Mar 31, 2021, 8:28:29 AM3/31/21

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On Wed, Mar 31, 2021 at 11:21 PM Loris Bennett
<loris....@fu-berlin.de> wrote:
>
> Hi,
>
> I want to get a list of users on a Linux system using Python 3.6. All
> the users I am interested in are just available via LDAP and are not in
> /etc/passwd. Thus, in a bash shell I can use 'getent' to display them.
>
> When I try to install the PyPi package
>
> getent
>
> I get the error
>
> File "/tmp/pip-build-vu4lziex/getent/setup.py", line 9, in <module>
> long_description = file('README.rst').read(),
> NameError: name 'file' is not defined
>
> I duckduckwent a bit and the problem seems to be that 'file' from Python
> 2 has been replaced by 'open' in Python 3.
>
> So what's the standard way of getting a list of users in this case?
>

I don't have LDAP experience so I don't know for sure, but is the
stdlib "pwd" module suitable, or does it only read /etc/passwd?

https://docs.python.org/3/library/pwd.html

Failing that, one option - and not as bad as you might think - is
simply to run getent using the subprocess module, and parse its
output. Sometimes that's easier than finding (or porting!) a library.

ChrisA

Loris Bennett

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Mar 31, 2021, 8:45:34 AM3/31/21

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D'oh! Thanks, 'pwd' is indeed exactly what I need. When I read the
documentation here

https://docs.python.org/3.6/library/pwd.html

I mistakenly got the impression that it was only going to give me the
local users. It doesn't actually say that, but it mentions /etc/shadow
and not getent. However, it does talk about the "account and password
database", which is a clue (although our passwords are on an other
system entirely), since "database" is more getent terminology.

In any case, I think 'pwd' is hiding its light under a bushel a bit
here.

Christian Heimes

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Mar 31, 2021, 10:25:06 AM3/31/21

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Please open a documentation bug :)

The pwd and grp module use the libc API to get users from the local
account database. On Linux and glibc the account database is handled by
NSS and nsswitch.conf.

By the way I recommend that you use SSSD instead of talking to LDAP
directly. You'll have a much more pleasant experience.

Christian

Loris Bennett

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Apr 1, 2021, 2:46:24 AM4/1/21

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I'll have a look :)

> The pwd and grp module use the libc API to get users from the local
> account database. On Linux and glibc the account database is handled by
> NSS and nsswitch.conf.
>
> By the way I recommend that you use SSSD instead of talking to LDAP
> directly. You'll have a much more pleasant experience.

Yes, we do use SSSD, but my grasp of what it does is pretty much limited
to "as well as looking at the local /etc/passwd it can also talk to
LDAP" :/