Once installed, checker is used by executing the checker script. This will look for a configuration, by default located in /config. The configuration location can be overriden with a command line options to the checker script:
checker -C /some/folder
Within the configuration folder, Checker looks for a file called checker.txt that contains a list of rows defining the configurations to be checked, for example:
path:/some/folder
path:/some/file
# blank lines and lines starting with hashes are ignored.
crontab:root
svn:/some/checkout
buildout:/some/buildout
Each one of these lines starts with the name of a checker followed by a colon. The remainder of the line is passed through to the checker for it to find the configuration information it should be checking. The checker may then write information to the configuration directory.
Once all the checkers have been run, an implict checker is run on the configuration folder itself. By default, the svn checker is used, but you can override this with a line in your checker.txt as follows:
config_checker:buildout
At the moment, the only sensible choices for the implicit checker are svn, buildout or svn,buildout to indicate the svn checker should be used followed by the buildout checker:
config_checker:svn,buildout
Note
The implicit checker is run only once all other checkers have been run. This means that if you have changes committed to the configuration folder that are not present in the working copy, they will only be retrieved once all other checkers have been run and so may only been show up in checker notifications when Checker is next run.
By default, any changes found by a checker are printed to stdout. This makes Checker ideal for running as a nightly cron job where the output will be emailed to the user running the cron job.
However, on some systems, output from scheduled tasks is not emailed to the user running the task. In this case, some special lines may be added to checker.txt as follows:
email_to: recipient1@example.com,recipient2@example.com
email_from: sender@example.com
email_subject: Checker output from myhost
email_smtphost: smtp.example.com
Only email_to is required, and once specified, if the other options are not present, the following defaults will be used:
If not specified, the subject will default to the text:
Checker output
followed by the hostname of the machine on which Checker is run.
It can be helpful to turn this behaviour off for manual runs where you know configurations have changes and you want to see output in your shell rather than by email. When that is the case, pass the --no-email option:
checker --no-email