The Apt layer is more code broken out from my PostgreSQL charm work
that will be used by future Cassandra charm work.
It provides a simple, charms.reactive friendly interface for dealing
with apt sources and deb packages. But I think its main utility is
providing consistent configuration for those extra features required
for real world production deploys without charmers needing to add a
single line of code; specifying custom apt sources, package signing
keys, package version pinning, and a list of arbitrary additional
packages to install. It also finally documents these options,
previously only found in the bowels of charmhelpers.core.fetch (which
provides the underlying implementation).
# Apt layer
The Apt layer for Juju enables layered charms to more easily deal with
deb packages and apt sources in a simple and efficient manner. It
provides consistent configuration for operators, allowing them to
easily specify custom apt sources and additional debs required for
their particular installations.
## Configuration
The charm may provide defaults for these service configuration
(config.yaml) options, and the operator may override them as required.
* `extra_packages`
A space separated list of additional deb packages to install on
each unit.
* `package_status`
'install' or 'hold'. When set to hold, packages installed using
the Apt layer API will be pinned, so that they will not be
automatically upgraded when package updates are performed. 'hold'
is particularly useful for allowing a service such as Landscape
to automatically apply security updates to most of the system,
whilst holding back any potentially service affecting updates.
* `install_sources`
A list of apt sources containing the packages that need to be installed.
Each source may be either a line that can be added directly to
sources.list(5), or in the form ppa:<user>/<ppa-name> for adding
Personal Package Archives, or a distribution component to enable.
The list is a yaml list, encoded as a string. The nicest way of
declaring this in a yaml file looks like the following (in particular,
the | character indicates that the value is a multiline string):
```
install_sources: |
- ppa:stub/cassandra
- deb http://www.apache.org/dist/cassandra/debian 21x main
```
* `install_keys`
A list of GPG signing keys to accept. There needs to be one entry
per entry in install_sources. null may be used if no keep is
needed, which is the case for PPAs and for the standard Ubuntu
archives. Keys should be full ASCII armoured GPG public keys.
GPG key ids are also accepted, but in most environments this
mechanism is not secure. The install_keys list, like
install_sources, must also be a yaml formatted list encoded as
a string:
```
install_keys: |
- null
- |
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1
mQINBFQJvgUBEAC0KcYCTj0hd15p4fiXBsbob0sKgsvN5Lm7N9jzJWlGshJ0peMi
kH8YhDXw5Lh+mPEHksL7t1L8CIr1a+ntns/Opt65ZPO38ENVkOqEVAn9Z5sIoZsb
AUeLlJzSeRLTKhcOugK7UcsQD2FHnMBJz50bxis9X7pjmnc/tWpjAGJfaWdjDIo=
=yiQ4
-----END PGP PUBLIC KEY BLOCK-----
```
## Usage
Queue packages for installation, and have handlers waiting for
these packages to finish being installed:
```
from reactive import apt
@hook('install')
def install():
apt.queue_install(['git'])
@when_not('apt.installed.gnupg')
def install_gnupg():
apt.queue_install(['gnupg'])
@when('apt.installed.git')
@when('apt.installed.gnupg')
def grabit():
clone_repo()
validate_repo()
```
### API
Several methods are exposed in the reactive.apt Python package.
* `add_source(source, key=None)`
Add an apt source.
A source may be either a line that can be added directly to
sources.list(5), or in the form ppa:<user>/<ppa-name> for adding
Personal Package Archives, or a distribution component to enable.
The package signing key should be an ASCII armoured GPG key. While
GPG key ids are also supported, the retrieval mechanism is insecure.
There is no need to specify the package signing key for PPAs or for
the main Ubuntu archives.
It is preferable if charms do not call this directly to hard
coded apt sources, but instead have these sources listed
as defaults in the install_sources config option. This allows
operators to mirror your packages to internal archives and
deploy your charm in environments without network access.
Sets the `apt.needs_update` reactive state.
* `queue_install(packages, options=None)`
Queue one or more deb packages for install. The actual package
installation will be performed later by a handler in the
apt layer. The `apt.installed.{name}` state will be set once
the package installed (one state for each package).
If a package has already been installed it will not be reinstalled.
If a package has already been queued it will not be requeued, and
the install options will not be changed.
* `installed()`
Returns the set of deb packages installed by this layer.
* `purge(packages)`
Purge one or more deb packages from the system
--
Stuart Bishop <stuart.bis...@canonical.com>
--
Juju mailing list
Juju@lists.ubuntu.com
Modify settings or unsubscribe at:
https://lists.ubuntu.com/mailman/listinfo/juju
