Speeding up the Travis Build to Decrease the Building Time

Meilix is the repository which uses build script to generate community version of lubuntu as LXQT Desktop. It usually takes around 25-26 to build and deploy the ISO as a Github Release on master branch.
Observing the build log we can see that there are most of the packages like debootstrap, squashfs-tool, etc which are being fetch and setup at the time of building which results in increasing build time.

The issue is to decrease the build time supplying the packages from Travis so that when we run build.sh we won’t be required to download them again and thus few minutes will get reduced.
We included list of packages to be pre-downloaded in .travis.yml

include:
  - os: linux
    addons:
      apt:
        sources:
          - ubuntu-toolchain-r-test
        packages:
          - debootstrap
          - genisoimage
          - p7zip-full
          - squashfs-tools
          - ubuntu-dev-tools
          - dpkg-dev
          - debhelper
          - fakeroot
          - devscripts

These are some important packages included in the build.sh  as devtools=”debootstrap genisoimage p7zip-full squashfs-tools ubuntu-dev-tools” which are always fetched, so we included it into .travis.yml and downloaded it before entering into the chroot environment. By specifying those packages in the .travis.yml, Travis provides those packages beforehand into the docker container so it will run our script. Since the scripts also include package then when the script runs apt-get it won’t download those packages again. They are specified outside the chroot environment because they are expected to be at the system the build.sh script is run to get the iso. By this way, we get a sharp decrease in build time as the internet in the Travis CI container is not so fast so the package download time can be avoided. Now the build is taking around 15-16 minutes to build and deploy.

One thing to note that we didn’t remove those packages off build.sh so that build.sh works outside Travis CI as well.

References:
Pull #176 by @abishekvashok
Speeding up Travis Build by Travis CI
Faster Build by atchai.com