Validate the fix¶

We need to validate the test in an isolated environment and LXC containers are a good tool for it.

Start a container¶

For example when investigating a segfault for bionic, start a bionic container.

We can name our LXC containers with any scheme we wish, such as ‘tester’ earlier for a temporary one to test with. However, for bug fixes we often need to keep the container around for reference as the bug fix goes through the review, sponsorship, and SRU processes.

So, to keep things consistent let’s reuse our Git branch name, and just prefix the package name:

$ lxc launch ubuntu:bionic postfix-sru-lp1753470-segfault-bionic
Creating postfix-sru-lp1753470-segfault-bionic
Starting postfix-sru-lp1753470-segfault-bionic

$ lxc exec postfix-sru-lp1753470-segfault-bionic -- bash
root@postfix-sru-lp1753470-segfault-bionic:~# 

Reproduce the bug¶

Record your steps as you go (you’ll need them later):

# apt dist-upgrade
# apt install -y postfix
# touch /etc/postfix/valiases.cf
# chmod 0600 /etc/postfix/valiases.cf
# echo "virtual_alias_maps = pgsql:/etc/postfix/valiases.cf" >> /etc/postfix/main.cf
# su - ubuntu
$ /usr/sbin/postconf virtual_alias_map
Segmentation fault (core dumped)

Install the fixed package¶

In this case, I’m using a PPA. Alternatively, if you’ve built locally, you can copy in the .deb file and install it manually.

$ sudo add-apt-repository -ys ppa:kstenerud/postfix-sru-lp1753470-segfault
$ sudo apt update
$ sudo apt upgrade -y

Test the bug again¶

$ /usr/sbin/postconf virtual_alias_map
/usr/sbin/postconf: warning: virtual_alias_map: unknown parameter

The bug is fixed! Sweet!