Best way to code rpm pre/post scripts

thespaceman · 03-23-2010, 04:16 PM

I'm having a few problems coding a post install script for my custom RPM package. I'm putting the script directly in the %post section of the spec files. For example if I wanted to add a user after the package is installed I would add the following code. The problem is capturing the output of the commands which should be stored in the variable.

%post
#Add some user (bob)

myuser=`grep ^bob: /etc/passwd`

# If myuser is empty then we have to add bob
if [ -z "$myuser" ]; then
useradd -u 123 -g 10 ..... -s /bin/sh bob
fi

The problem seems to be that myuser is always null even if bob exists in /etc/passwd.

What's wrong with this code and should I use an external script instead?
TIA

unSpawn · 03-23-2010, 07:29 PM

You don't need to store in a variable as you can use the exit code directly. First turn to common utilities like 'id' and such, else use something like 'awk' or 'grep', so why not simply

Code:

id apache >/dev/null|| adduser --lotsa-args

? Of course the user name has to be unique for such an example to work.

thespaceman · 03-24-2010, 12:04 AM

OK thanks for the reply. As this package only needs a user to be created this is quite straightforward and I can use the return codes from id etc as you have suggested.

Just so that I can understand this better what is the problem with trying to store values returned from commands in variables within RPM scripts? Is this possible or was RPM designed with this 'feature' and if so can we only use return codes within test expressions?

Are there any good examples available of pre/post scripts that could shed some light on this?

unSpawn · 03-24-2010, 03:38 AM

There's no problem storing variables as RPM uses "plain" shell scripts. This works:

Code:

%post
if [ $1 -eq 1 ]; then
	# This package is being installed for the first time
	echo "Post: installing %{name}"
	myuser=$(grep '^bob:' /etc/passwd 2>/dev/null)
	if [ ${#myuser} -eq 0 ]; then
		echo "Post: useradd ... bob"
	fi
else
	# This is an upgrade
fi

If you have any problems with it please add debug statements to your %post scripts that echo variables and contents and post the output.