Introduction
Heads up, this is very preliminary and meant to be a base our next design conversations on how we want this to look like. It uses a fictional fedora27 base as seen in the snapcraft.yaml:
name: make-hello
version: 0.1
summary: test the make plugin
description: |
This is a basic make snap. It just prints a hello world.
If you want to add other functionalities to this snap, please don't.
Make a new one.
confinement: strict
base: fedora27
build-packages: [gcc]
apps:
make-hello:
command: test
parts:
make-project:
plugin: make
source: .
To determine it needs to use a specific build environment to build for that base,
sergiusens@mirkwood:~/source/snapcraft/tests/integration/snaps/make-hello$ snapcraft pull
Creating a build environment named 'multibranchiate-katlyn'
[sudo] password for sergiusens:
qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.80000001H:ECX.svm [bit 2]
Waiting for pending snap auto refreshes.
Connected (version 2.0, client OpenSSH_7.6)
Authentication (publickey) successful!
Refreshing snapcraft in 'multibranchiate-katlyn'
Connected (version 2.0, client OpenSSH_7.6)
Authentication (publickey) successful!
error: cannot refresh "snapcraft": snap "snapcraft" has "auto-refresh" change
in progress
Connected (version 2.0, client OpenSSH_7.6)
Authentication (publickey) successful!
Connected (version 2.0, client OpenSSH_7.6)
Authentication (publickey) successful!
Last metadata expiration check: 3:52:33 ago on Thu 24 May 2018 09:55:45 PM UTC.
Package make-1:4.2.1-4.fc27.x86_64 is already installed, skipping.
Dependencies resolved.
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
gcc x86_64 7.3.1-5.fc27 updates 21 M
Installing dependencies:
binutils x86_64 2.29-13.fc27 updates 5.9 M
cpp x86_64 7.3.1-5.fc27 updates 9.4 M
glibc-devel x86_64 2.26-28.fc27 updates 990 k
glibc-headers x86_64 2.26-28.fc27 updates 505 k
isl x86_64 0.16.1-3.fc27 fedora 835 k
kernel-headers x86_64 4.16.9-200.fc27 updates 1.2 M
libmpc x86_64 1.0.2-8.fc27 fedora 56 k
Transaction Summary
================================================================================
Install 8 Packages
Total download size: 40 M
Installed size: 111 M
Downloading Packages:
(1/8): isl-0.16.1-3.fc27.x86_64.rpm 89 kB/s | 835 kB 00:09
(2/8): libmpc-1.0.2-8.fc27.x86_64.rpm 82 kB/s | 56 kB 00:00
(3/8): binutils-2.29-13.fc27.x86_64.rpm 105 kB/s | 5.9 MB 00:58
(4/8): glibc-devel-2.26-28.fc27.x86_64.rpm 115 kB/s | 990 kB 00:08
(5/8): glibc-headers-2.26-28.fc27.x86_64.rpm 74 kB/s | 505 kB 00:06
(6/8): kernel-headers-4.16.9-200.fc27.x86_64.rp 83 kB/s | 1.2 MB 00:15
(7/8): cpp-7.3.1-5.fc27.x86_64.rpm 89 kB/s | 9.4 MB 01:48
(8/8): gcc-7.3.1-5.fc27.x86_64.rpm 99 kB/s | 21 MB 03:41
--------------------------------------------------------------------------------
Total 184 kB/s | 40 MB 03:45
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
Preparing : 1/1
Installing : libmpc-1.0.2-8.fc27.x86_64 1/8
Running scriptlet: libmpc-1.0.2-8.fc27.x86_64 1/8
Installing : cpp-7.3.1-5.fc27.x86_64 2/8
Running scriptlet: cpp-7.3.1-5.fc27.x86_64 2/8
Installing : kernel-headers-4.16.9-200.fc27.x86_64 3/8
Running scriptlet: glibc-headers-2.26-28.fc27.x86_64 4/8
Installing : glibc-headers-2.26-28.fc27.x86_64 4/8
Installing : glibc-devel-2.26-28.fc27.x86_64 5/8
Running scriptlet: glibc-devel-2.26-28.fc27.x86_64 5/8
Installing : binutils-2.29-13.fc27.x86_64 6/8
Running scriptlet: binutils-2.29-13.fc27.x86_64 6/8
Installing : isl-0.16.1-3.fc27.x86_64 7/8
Running scriptlet: isl-0.16.1-3.fc27.x86_64 7/8
Installing : gcc-7.3.1-5.fc27.x86_64 8/8
Running scriptlet: gcc-7.3.1-5.fc27.x86_64 8/8
Running as unit: run-racf224037296449fb6618b0d6321ff0d.service
Verifying : gcc-7.3.1-5.fc27.x86_64 1/8
Verifying : cpp-7.3.1-5.fc27.x86_64 2/8
Verifying : isl-0.16.1-3.fc27.x86_64 3/8
Verifying : libmpc-1.0.2-8.fc27.x86_64 4/8
Verifying : binutils-2.29-13.fc27.x86_64 5/8
Verifying : glibc-devel-2.26-28.fc27.x86_64 6/8
Verifying : glibc-headers-2.26-28.fc27.x86_64 7/8
Verifying : kernel-headers-4.16.9-200.fc27.x86_64 8/8
Installed:
gcc.x86_64 7.3.1-5.fc27 binutils.x86_64 2.29-13.fc27
cpp.x86_64 7.3.1-5.fc27 glibc-devel.x86_64 2.26-28.fc27
glibc-headers.x86_64 2.26-28.fc27 isl.x86_64 0.16.1-3.fc27
kernel-headers.x86_64 4.16.9-200.fc27 libmpc.x86_64 1.0.2-8.fc27
Complete!
Preparing to pull make-project
Pulling make-project
Preparing to build make-project
Building make-project
make -j1
gcc -o test test.c
make install DESTDIR=/multibranchiate-katlyn/parts/make-project/install
mkdir -p /multibranchiate-katlyn/parts/make-project/install/bin
cp -a test /multibranchiate-katlyn/parts/make-project/install/bin/
Staging make-project
Priming make-project
Files from the build host were migrated into the snap to satisfy dependencies that would otherwise not be met. This feature will be removed in a future release. If these libraries are needed in the final snap, ensure that the following are either satisfied by a stage-packages entry or through a part:
lib64/libc.so.6
'grade' property not specified: defaulting to 'stable'
Snapping 'make-hello' \
Snapped make-hello_0.1_amd64.snap
How
Build VM
The build VM is based out of a Fedora 27 cloud image, using cloud-init for some initial customization such as preinstalling snapd and snapcraft and to have a warm dnf cache.
The cloud-config is very bare bones:
#cloud-config
package_update: true
package_upgrade: true
packages:
- nc
- kernel-modules
- cloud-utils-growpart
- snapd
growpart:
mode: auto
devices: ['/']
After this cycle is done, I shutdown and removed the cloud seed that was created.
snapcraft
In snapcraft there’s a minimal cloud-config which sets up a build user and ssh keys for that user.
It launches qemu with the following characteristics,
- a
9pmount point for the project. - a monitor using telnet to talk to the qemu control pane.
- a port forward to port 22 for ssh.
snapcraft monitors the readiness of the ssh port and uses paramiko to send commands over to refresh, mount the project and later run snapcraft.
Once that is done, the telnet port is used to save the vm state (i.e.; qemu’s savevm) and then shutdown.
There are a couple of shortcuts taken here, one not mentioned is that there is a very minimal Repo handler for dnf which we would move to the build environment setup once that is done, more on that on the Build environment file format topic.
A keen eye can also see that the exact lifecycle command is not being passed on and a full snap is always created (that’s just a bit more of integration work I did not have time to get to yet).