For security reasons, symlinks are disabled in IkiWiki. That's fair enough, but that means that some problems, which one could otherwise solve by using a symlink, cannot be solved. The specfic problem in this case is that all underlays are placed at the root of the wiki, when it could be more convenient to place some underlays in specific sub-directories.

Use-case 1 (to keep things tidy):

Currently IkiWiki has some javascript files in underlays/javascript; that directory is given as one of the underlay directories. Thus, all the javascript files appear in the root of the generated site. But it would be tidier if one could say "put the contents of this underlaydir under the js directory".

Of course, this could be accomplished, if we wanted to, by moving the files to underlays/javascript/js. --Joey

Use-case 2 (a read-only external dir):

Suppose I want to include a subset of /usr/local/share/docs on my wiki, say the docs about foo. But I want them to be under the docs/foo sub-directory on the generated site. Currently I can't do that. If I give /usr/local/share/docs/foo as an underlaydir, then the contents of that will be in the root of the site, rather than under docs/foo. And if I give /usr/local/share/docs as an underlaydir, then the contents of the foo dir will be under foo, but it will also include every other thing in /usr/local/share/docs.

Since we can't use symlinks in an underlay dir to link to these directories, then perhaps one could give a specific underlay dir a specific prefix, which defines the sub-directory that the underlay should appear in.

I'm not sure how this would be implemented, but I guess it could be configured something like this:

prefixed_underlay => {
     'js' => '/usr/local/share/ikiwiki/javascript',
     'docs/foo' => '/usr/local/share/docs/foo',

So, let me review why symlinks are an issue. For normal, non-underlay pages, users who do not have filesystem access to the server may have commit access, and so could commit eg, a symlink to /etc/passwd (or to / !). The guards are there to prevent ikiwiki either exposing the symlink target's contents, or potentially overwriting it.

Is this a concern for underlays? Most of the time, certianly not; the underlay tends to be something only the site admin controls. Not all the security checks that are done on the srcdir are done on the underlays, either. Most checks done on files in the underlay are only done because the same code handles srcdir files. The one exception is the test that skips processing symlinks in the underlay dir. (But note that the underlay directory can be a symlinkt to elsewhere which the srcdir, by default, cannot.)

So, one way to approach this is to make ikiwiki follow directory symlinks inside the underlay directory. Just a matter of passing follow => 1 to find. (This would still not allow individual files to be symlinks, because readfile does not allow reading symlinks. But I don't see much need for that.) --Joey

If you think that enabling symlinks in underlay directories wouldn't be a security issue, then I'm all for it! That would be much simpler to implement, I'm sure. --KathrynAndersen