[Debian-med-packaging] Bug#739657: Maintainer scripts: execute command as another user: use sudo or su?

[Emilien Klein]

Hi Mentors,

TLDR: in order to execute a command as another user, should `sudo` or
`su --command` be used?


I'd like to get your opinion on how to best solve this issue:
I've got a package [0] that uses dbconfig-common to manage its
database. The database is owned by a specific user (not root).

In the pre- and postinst scripts, a command has to be performed as
that user (e.g. make a backup of the database).

I've at first used sudo to perform that, and it worked fine until
piuparts found an issue [1], since (as I hadn't realized) sudo is not
part of the base system (installed on 76% of popcon-reporting machines
[2])


I am wondering what the best way is to fix this. I see 2 solutions:
1. Depend on sudo
2. Use "su --command" instead


First lines from the respective manpages:
sudo, sudoedit - execute a command as another user
su - change user ID or become superuser


Following the Unix philosophy of using a collection of specialized
small tools that do one thing best, when performing an action as
another user it seems to be the correct thing to use a tool that
"execute a command as another user" rather than one whose primary goal
is "change user ID or become superuser".

But on the other hand, su is part of corutils (which is in the base
install), so using su would remove the need of installing a new
package for about 25% of our users.

What are your thoughts on this?

Thanks for getting a fellow Debian Maintainer out of his confusion!
(and let's hope it doesn't turn into a vi vs. Emacs debate ;) )
   +Emilien

[0] http://pts.debian.net/pkg/gnuhealth
[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=739657
[2] Looking at popcon (obvious notice about [un]reliability of that
data applies) data from 2014-02-24:
- There are 167453 registered popcon users that sent information
- corutils (package that amongst others, contains su) sports 167451
installations (99.998% of installs) [3]
- sudo reports 127695 installations (76% of installs) [4]
[3] http://qa.debian.org/popcon.php?package=sudo
[4] http://qa.debian.org/popcon.php?package=coreutils