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Containers with systemd-nspawn

Project description

nspawn

Travis Status Appvey Status Package Version Python Versions

Containers with systemd-nspawn

Features:

Install

To install python package:

sudo pip install nspawn

Build Script

To build an image, provide and invoke executable build.py script, for example:

For available build options run ./build.py --help

Setup Script

To setup a machine, provide and invoke executable setup.py script, for example:

For available setup options run ./setup.py --help

Machine Service

To review provisioned, generated and running machine service, run:

machinectl
systemctl status <machine>
cat /etc/systemd/system/<machine>.service

for example, demo generated services:

Machine Resources

Location of machine files and folders:

/etc/systemd/system/<machine>.service
/var/lib/machines/<machine>
/var/lib/nspawn/runtime/<machine>

Machine Management

To interact with live machine:

  • for machines registered with machinectl
  • for machines with systemd init, such as archlinux
# start interactive shell:
sudo machinectl shell <machine> 
# invoke command with args:
sudo machinectl shell <machine> /bin/command arg1 arg2 ... 
  • for machines not registered with machinectl
  • for machines without systemd init, such as alpine linux
# start interactive shell:
./setup.py --action=nsenter 
  • alternatively, use package-provided nspawn-enter command:
# start interactive shell:
nspawn-enter <machine> 
# invoke command with args:
nspawn-enter <machine> "command arg1 arg2 ..." 

Configuration

Available configuration options are described in config.ini file.

Use config/path_list option to control configuration override file list.

Image Server

Package comes with provisioning command nspawn-hatch which can build and setup local http/https image server.

# review available services:
nspawn-hatch list
# provision image server service:
nspawn-hatch update image-server
# verify image server machine status:
machinectl

Image server settings:

Build DSL

Build DSL is used in build.py, is activated by from nspawn.build import * and provides keywords:

    'TOOL',
    'IMAGE',
    'PULL',
    'EXEC',
    'WITH',
    'FETCH',
    'COPY',
    'CAST',
    'RUN',
    'SH',
    'PUSH',

Setup DSL

Setup DSL is used in setup.py, is activated by from nspawn.setup import * and provides keywords:

    'TOOL',
    'IMAGE',
    'MACHINE',
    'WITH',
    'EXEC',
    'COPY',
    'CAST',
    'RUN',
    'SH',

DSL Syntax

TOOL

Expose build/setup utility functions:

TOOL.<function>(...)

IMAGE()

Declare image identity:

IMAGE("http://host/path/package.tar.gz")
IMAGE(url="http://host/path/package.tar.gz")

PULL()

Provision dependency image:

PULL("http://host/path/package.tar.gz")
PULL(url="http://host/path/package.tar.gz")

EXEC()

Declare image entry point executable i.e. COMMAND [ARGS...]:

EXEC(['/usr/bin/env', 'sh', '-c', 'echo "hello-kitty"'])
EXEC(command=['/usr/bin/env', 'sh', '-c', 'echo "hello-kitty"'])

WITH()

Customize machine features using nspawn container settings:

WITH(
    SettingName1='setting 1 value a',
    SettingName2='setting 2 value b',
    ...,
)

COPY()

Copy local resources:

  • when used in build.py: target is in the image
  • when used in setup.py: target is on the host
COPY("/etc")
COPY(path="/etc")
COPY(source="/root/input.md", target="/root/output.md")

CAST()

Template local resources:

  • when used in build.py: target is in the image
  • when used in setup.py: target is on the host
CAST("/root/readme.md", variable="template varialbe", ...)
CAST(path="/root/readme.md", variable="template varialbe", ...)
CAST(source="/root/input.md", target="/root/output.md", variable="template varialbe", ...)

Template uses python/jinja format, i.e:

this template variable will be substituted: {{variable}}

FETCH()

Download and extract remote resource:

FETCH( # use when source and target are the same
   url="http://server/package.tar.gz", # url for remote resource
   path="/common-path", # path inside the package source and image target
)
FETCH( # use when source and target are different
   url="http://server/package.tar.gz", # url for remote resource
   source="/package-path", # path inside the package extract
   target="/opt/resource", # path inside the build image target
)

RUN()

Invoke command, with target depending on the context:

  • when used in build.py: invoke inside the image
  • when used in setup.py: invoke on the host
RUN(['/usr/bin/env', 'ls', '-las'])
RUN(command=['/usr/bin/env', 'ls', '-las'])

SH()

Invoke shell script, with target depending on the context:

  • when used in build.py: invoke inside the image
  • when used in setup.py: invoke on the host
SH("ls -las")
SH(script="ls -las")

Note:

  • SH(script) is equivalent to RUN(command=['/usr/bin/env', 'sh', '-c', script])

PUSH()

Publish image result to the declared url:

PUSH()

MACHINE()

Declare machine service:

MACHINE('machine-name')
MACHINE(name='machine-name')
MACHINE(name='machine-name', template='/path/to/service/template/machine.service')

Design custom service templates based on package-provided defaults, for example:

Project details


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