[RFC] incorrect parsing of sysusers.d in rootfs generation

[Louis Rannou <lrannou@baylibre.com>]

Hello,

I have found an issue in the rootfs routine. The 
rootfs-postcommands.bbclass has a funtion systemd_create_users that 
reads /etc/sysusers.d/*.conf files and parses lines as 'type name id 
comment'.

However, the sysusers.d manual says, those lines can be 'type name id 
comment home_dir shell'. If a home directory of shell is defined, they 
are considered as part of the comment, and we run incorrect commands 
such as the one below :

useradd --shell /sbin/nologin --uid 0 --comment "Super User" /root 
--system root

To fix that, we require a stronger parsing. Several options look 
possible to me, but I am not sure which one is preferred.

1. sed with a regular expression that returns something that still needs 
parsing
2. awk with a step by step script that returns something that still 
needs to be parsed
3. use python and regexp module

Also I don't know if the parsing should completely check the sysusers 
syntax as said in the manual (first field is [urgm], second is 
alphanum_-, etc.). In my opinion it should not as this will be made by 
the useradd command.

Do you think it worth to add some testing about that ? I am not sure how 
to do that.

Regards,
Louis Rannou