Implement #9650 Add parameter hooks to inventory plugin iocage

[vbotka]

SUMMARY

Implement #9650 Add parameter hooks to inventory plugin iocage.

ISSUE TYPE

• Feature Pull Request

COMPONENT NAME

iocage.py

ADDITIONAL INFORMATION

Tested in Ubuntu 24.04

[felixfontein]

Thanks for your contribution!

I'm wondering a bit about the term hook. Is this some nomenclature that's used in the iocage surroundings for such things? If not, maybe another name would be better. I'm not very good at coming up with names, but maybe something like read_file_contents, resulting in iocage_file_contents being set?

[felixfontein]

Maybe a warning should be printed in this case? (Or the behavior should be configurable - ignore, warn, error.)

[vbotka]

The jails may be heterogeneous, and a hook that works for one jail may not work for the other. I want to keep the spirit of silently ignoring No such file or any other error:

1. I don't want to complicate the use case where different jails use different hooks or no hooks at all. Just list all hooks and let the compose option pick what is needed.

2. The dash "-" is used in iocage to represent a missing value. See for example ioc_list.py#L259 or ioc_list.py#L276. We've already used it too:

if iocage_ip4_dict['ip4']:
    iocage_ip4 = ','.join([d['ip'] for d in iocage_ip4_dict['ip4']])
else:
    iocage_ip4 = '-'

3. The admins should be responsible for intercepting anything. And they should be used to it, especially in the case of the hooks. For example, the /etc/dhclient-enter-hooks and /etc/dhclient-exit-hooks silently ignore any failing lines in the scripts. It is expected, that the admin is responsible for checking what a hook is doing. There are also security implications.

We can add the options (ignore, warn, error) later if needed.

[felixfontein]

Same here.

Also, why not using None instead of -? None can never appear as a real value, so you can distinguish "error happened" from "- was actually read".

[vbotka]

I'm wondering a bit about the term hook. Is this some nomenclature that's used in the iocage surroundings for such things? If not, maybe another name would be better.

The nomenclature is general. A hook is a method to intercept . For example,

• Linux kernel hooking library
• Using ftrace to hook to functions
• Package maintainer scripts and hooks

In particular, dhclient-script says:

... dhclient-script will check for the existence of /etc/dhclient-enter-hooks. If found, it will be sourced (see sh(1)). After taking action according to $reason, dhclient-script will check for the existence of /etc/dhclient-exit-hooks. If found, it will be sourced (see sh(1)). These hooks scripts can be used to dynamically modify the environment at appropriate times during the DHCP negotiations.

There is no better name.