This page describes the step-by-step process of writing a client tool
driver for a configuration element type. The included example describes
an existing driver, and the process that was used to create it.
Pick a name for the driver. In this case, we picked the name RPM.
Create a file in src/lib/Client/Tools with the same name (RPM.py)
Create a class in this file with the same name (class RPM)
If it handles Package entries, subclass Bcfg2.Client.Tools.PkgTool
(from here referenced as branch [P])
If it handles Service entries, subclass Bcfg2.Client.Tools.SvcTool
(from here referenced as branch [S])
Otherwise, subclass Bcfg2.Client.Tools.Tool (from here referenced
as branch [T])
Set name to “RPM”
Add any required executable programs to __execs__
Set __handles__ to a list of (entry.tag, entry.get(‘type’))
tuples. This determines which entries the Tool module can be used
on. In this case, we set __handles__=[('Package','rpm')].
Add verification. This method should return True/False depending
on current entry installation status.
[T] Add a Verify<entry.tag> method.
[P] Add a VerifyPackage method.
[S] Add a VerifyService method.
In the failure path, the current state of failing entry
attributes should be set in the entry, to aid in auditing.
(For example, if a file should be mode 644, and is currently
mode 600, then set attribute current_perms=‘600’ in the input
Add installation support. This method should return True/False
depending on the results of the installation process.
[T,S] Add an Install<entry.tag> method.
[P] The PkgTool baseclass has a generic mechanism for performing
all-at-once installations, followed, in the case of failures,
by single installations. To enable this support, set the pkgtype
attribute to the package type handled by this driver. Set the
pkgtool to a tuple (“command string %s”, (“per-package string
format”, [list of package entry fields])). For RPM, we have
Implement entry removal
[T,S] Implement a Remove method that removes all specified
[P] Implement a RemovePackages that removes all specified
entries (same prototype as Remove)
Add a FindExtra method that locates entries not included in the
configuration. This may or may not be required, certain drivers
do not have the capability to find extra entries.
[P] Package drivers require a RefreshPackages method that updates
the internal representation of the package database.