User:Allan/Pacman Hooks - Version 1
Short Version: Pacman should have hooks to perform common tasks.
Long Version: Many packages have install files that perform a common task; e.g. adding/removing info files in the info directory file, installing/uninstalling gconf schemas, updating the font/desktop/icon cache. It would be good if pacman was extendible through a hooks mechanism so that these could be handled automatically.
A hook would need
- Information on when the hooks should be run (see "Types of Hooks" below)
- A list of files or globs that trigger the running of the hook, alternative a package name that trigger the hook
- The actual hook script
Types of Hook
Hooks need to be able to cover a variety of tasks. The following types of hooks are a minimum necessary:
- Hooks run once per transaction (e.g. updating font cache). These would be run whenever a transaction touches a trigger file (both install and uninstall).
- Hooks that run for every matching file (e.g. updating the info directory). Separate versions would be needed for install and removal of the files.
- Hooks that run for every matching package. As with files there would be separate versions would be needed for install and removal of the files.
Proposed Directory Layout
/etc/pacman.d/hooks.conf /hooks.d/info-install info-remove ttf etc-install Postkernelupdate
(Dan: why bother with 'hooks.d/' and not just 'hooks/'?)
(Allan: can't really comment given I actually have no idea what the .d is for with folders in /etc)
(Jeff: .d is a very loose standard that signifies a configuration _d_irectory for a given package. This is usually for packages that have multiple config files to avoid cluttering /etc. If there is a config file named the same as the directory (suffix excluded) it is starting to become customary to add the .d. With that in mind, if there is no hooks.conf then hooks.d may as well be just hooks. Either way, it is just a preference, not a standard.)
Example Config File
This is presented for comments. Many improvements are likely...
[info-install] Files = /usr/share/info/* Run = Install [info-remove] Files = /usr/share/info/* Run = PreRemove [etc-install] Files = /etc/* Run = Install [ttf] Files = /usr/share/fonts/TTF/* Run = Transaction #Example of packagetriggered hook: [Postkernelupdate] Package = kernel26 Run = PostInstall
Alternative Configfilesyntax (only showing some of the examples above):
[Install] Files = /usr/share/info/* Run = info-install Files = /etc/* run = etc-install [PreRemove] Files = /usr/share/info/* Run = info-remove [PostInstall] Package = kernel26 Run = Postkernelupdate
Allan: We should allow for the possibility of multiple files lines.
Mårten: In the alternative syntax the section header signals when in time to peform the action and the "Run" parameter is the script to run (better keyword?). I think it gives a more natural header for the different sections and the section headers have more static content which may help the parsing of the configfile.
Options that will be needed to cover the general range of tasks to be performed by hooks (may need to be more general...):
- Install - run on installation of a matching file/package
- PostInstall - run after installation of a matching file/package
- PreRemove - run prior to removal of a matching file/package
- PostRemove - run after to removal of a matching file/package
- Transaction - run at end of transaction involving at least one matching file
We should probably lean on the side of generality here and add options to cover all functions in the install files. Who knows what uses people could find for this...
Dan: so to make it clear: The first three hooks run on a per-package basis, and the Transaction hook would only run once for our entire pacman operation, correct?
Allan: The frist three run on a per matching file basis but otherwise correct. I'm not sure if the by-file hooks should run after each package or at the end of the transaction.
Hook Script Notes
Hooks that are run once per transaction do not need to know what file triggered them (Dan: do we want to rule out the possibility of providing this information?) but hooks that are run once per file will need to be passed the file name.
Allan: By the nature of the per-transaction hooks, they should not need file names. Otherwise they should be per-file hooks. This would also mean parsing and passing a list.