Ubuntu 16.04: Install and build snap package

A snap package includes private root filesystem which has libraries required by package. This will protect dependency of libraries for each package but duplicated libraryes will make size of system be large.

For example, the private root filesystem of bluez is as below.

$ tree /snap/bluez/6/
/snap/bluez/6/
├── command-bluetoothctl.wrapper
├── command-bluez.wrapper
├── command-obexctl.wrapper
├── command-obex.wrapper
├── meta
│   ├── gui
│   │   └── icon.png
│   └── snap.yaml
└── usr
    ├── bin
    │   ├── bluetoothctl
    │   └── obexctl
    ├── lib
    │   ├── bluetooth
    │   │   ├── bluetoothd
    │   │   └── obexd
    │   └── x86_64-linux-gnu
    │       ├── libical.so.1 -> libical.so.1.0.1
    │       ├── libical.so.1.0.1
    │       ├── libicalss.so.1 -> libicalss.so.1.0.1
    │       ├── libicalss.so.1.0.1
    │       ├── libicalvcal.so.1 -> libicalvcal.so.1.0.1
    │       └── libicalvcal.so.1.0.1
    └── share
        └── doc
            ├── bluez
            │   ├── copyright
            │   └── overview.md
            └── libical1a
                └── copyright

The snapd is a tool for installing snap package. This name may be changed from snappy to snapd.

$ sudo apt install -y snapd

ab alsa-utils apktool atom-cwayne audovia base beagleblack bluez
canonical-dragon canonical-i386 canonical-pc canonical-pc-linux
canonical-pi2 cassandra cla-check compass-straightedge drmips eeevil
ejabberd filebot foobar21 freecad freechartgeany gdoc-html-cleaner
ghex-udt gmailfilter gnuchess go-example-webserver hangups hello
hello-huge hello-snap hello-world htop http jenkins john-the-ripper
kale keepassx-elopio kpcli-elopio krita languagetool links
littlewatcher minecraft-server-jdstrand miniterm-joc moon-buggy
morse-converter-py nextcloud nikola nmap notes open-solitaire-classic
openscad-plars owncloud pciutils pen roseapple-pi scummvm serial-vault
shadowsocks shout simplenote-jamiebennett snapd-hacker-toolbelt
snappy-debug snapstore-example speed-test spread sshtron
stellarium-plars sudo systesterpro64 taskwarrior-plars teatime-unity
telegram-sergiusens tic-tac-toe tio tor-middle-relay tpad tproxy
ubuntu-calculator-app ubuntu-clock-app ubuntu-core ufw vaca
vault-elopio vlc vtop webcam-webui-stylerrr webdm x11-apps
xkcd-webserver xkcdpass-codersquid yacas yagy

snap package structure is following.

$ mount | grep snap
/var/lib/snapd/snaps/ubuntu-core_122.snap on /snap/ubuntu-core/122 type squashfs (ro,relatime)
/var/lib/snapd/snaps/jenkins_6.snap on /snap/jenkins/6 type squashfs (ro,relatime)

The snapcraft is a tool for building snap package.

$ sudo apt install -y snapcraft

$ sudo apt install -y snapcraft-examples
$ ls /usr/share/doc/snapcraft-examples/examples/git
96boards-kernel             godd              mosquitto    ros                  webchat
busybox                     gopaste           opencv       shout
downloader-with-wiki-parts  java-hello-world  py2-project  tomcat-maven-webapp
git                         libpipeline       py3-project  webcam-webui

$ cp -a /usr/share/doc/snapcraft-examples/examples/git .
$ cd git
$ tree
.
├── setup
│   └── gui
│       └── icon.png
└── snapcraft.yaml

$ cat snapcraft.yaml
name: git
version: 2.8.0
summary: Git is a free and open source distributed version control system.
description: This example is not really production quality
confinement: strict

apps:
  server:
    command: bin/git

parts:
  git:
    plugin: make
    source: https://github.com/git/git
    source-type: git
    make-parameters:
      - prefix=
    build-packages: [gettext, libssl-dev, libcurl4-openssl-dev, libexpat1-dev]

$ snapcraft list-plugins
ant        catkin  copy  jdk     kernel  maven  nodejs   python3 tar-content
autotools  cmake   go    kbuild  make    nil    python2  scons

$ snapcraft
$ sudo snap install git_2.8.0_amd64.snap
$ ls /snap/git
current  x1

This article will use tetris source code which uses simple Makefile.

Building tetris source code without snapcraft is as below. This will create jni/src/ncurses command and jni/src/sdl command.

$ sudo apt install -y libsdl2-dev libsdl2-image-dev \
libsdl2-ttf-dev libncurses5-dev
$ git clone https://github.com/hiroom2/tetris-sdl-and-ncurses
$ cd tetris-sdl-and-ncurses
$ make
$ ./jni/src/ncurses # or ./jni/src/sdl

Create work directory and generate snapcraft.yml template with "snapcraft init".

$ mkdir tetris
$ snapcraft init # Generate template snapcraft.yml

Change snapcraft.yml as below. /snap/bin/<package>.<component> and wrapper script will be created by apps directive.

$ cat snapcraft.yaml
name: tetris
version: 1.0
summary: tetris with ncurses or sdl2
description: https://github.com/hiroom2/tetris-sdl-and-ncurses
confinement: strict

# /snap/bin/<package>.<component>
apps:
  sdl:
    command: bin/sdl
  ncurses:
    command: bin/ncurses

# Build package
parts:
  tetris:
    plugin: make
    source: https://github.com/hiroom2/tetris-sdl-and-ncurses
    source-type: git
    build-packages: [libsdl2-dev, libsdl2-image-dev, libsdl2-ttf-dev, libncurses5-dev]

Build snap package.

$ snapcraft
Preparing to pull tetris
Pulling tetris
Cloning into '/home/hiroom2/tetris/parts/tetris/src'...
remote: Counting objects: 26, done.
remote: Compressing objects: 100% (24/24), done.
remote: Total 26 (delta 1), reused 25 (delta 1), pack-reused 0
Unpacking objects: 100% (26/26), done.
Checking connectivity... done.
Preparing to build tetris
Building tetris
make -j1
make -C jni/src
make[1]: Entering directory '/home/hiroom2/tetris/parts/tetris/build/jni/src'
rm -rf sdl ncurses *.dSYM
g++ -Wall -I.  `sdl2-config --cflags` -o sdl Tetris.cpp TetrisSDL.cpp SDL.cpp -lpthread -lSDL2 -lSDL2_ttf
g++ -Wall -I. -o ncurses Tetris.cpp TetrisNcurses.cpp ncurses.cpp -lpthread -lncurses
make[1]: Leaving directory '/home/hiroom2/tetris/parts/tetris/build/jni/src'
make install DESTDIR=/home/hiroom2/tetris/parts/tetris/install
install -d -m755  /home/hiroom2/tetris/parts/tetris/install/bin/
install -m755 jni/src/sdl /home/hiroom2/tetris/parts/tetris/install/bin/
install -m755 jni/src/ncurses /home/hiroom2/tetris/parts/tetris/install/bin/ncurses
Staging tetris
Priming tetris
Snapping 'tetris' -
Snapped tetris_1.0_amd64.snap

Install snap package.

$ sudo snap install tetris_1.0_amd64.snap

Name    Version  Rev  Developer  Notes
tetris  1.0      x1              -

/snap/tetrisにsquashfs is mounted.

$ tree /snap/tetris/
/snap/tetris/
├── current -> x1
└── x1
    ├── bin
    │   ├── ncurses
    │   └── sdl
    ├── command-ncurses.wrapper
    ├── command-sdl.wrapper
    ├── meta
    │   └── snap.yaml
    └── usr
        └── lib
            └── x86_64-linux-gnu
                ├── libasound.so.2
                ├── libasyncns.so.0
                ├── libFLAC.so.8
                ├── libogg.so.0
                ├── libpulse.so.0
                ├── libSDL2-2.0.so.0
                ├── libSDL2_ttf-2.0.so.0
                ├── libsndfile.so.1
                ├── libsndio.so.6.1
                ├── libvorbisenc.so.2
                ├── libvorbis.so.0
                ├── libwayland-client.so.0
                ├── libwayland-cursor.so.0
                ├── libwayland-egl.so.1
                ├── libX11.so.6
                ├── libXau.so.6
                ├── libxcb.so.1
                ├── libXcursor.so.1
                ├── libXdmcp.so.6
                ├── libXext.so.6
                ├── libXfixes.so.3
                ├── libXinerama.so.1
                ├── libXi.so.6
                ├── libxkbcommon.so.0
                ├── libXrandr.so.2
                ├── libXrender.so.1
                ├── libXss.so.1
                ├── libXxf86vm.so.1
                └── pulseaudio
                    └── libpulsecommon-8.0.so

/snap/bin/<package>.<component> is added.

$ ls /snap/bin/tetris.*
/snap/bin/tetris.ncurses  /snap/bin/tetris.sdl