Extraction only¶

You can also run the process step by step, for example, this will only extract the manpages:

debmans -m /srv/mirror -o html extract

Note that extract creates a cache in the output directory to avoid re-extracting already found archives. Render also uses a caching mechanism by not converting to HTML if the HTML version is newer than the manpage. Those mechanisms can be disabled with --no-cache.

debmans -m /srv/mirror -o html --no-cache extract

You can make a trial run with the -n flag and enable more verbose logging:

debmans -v -n -m /srv/mirror -o manpages extract

Rendering only¶

Rendering the pages can be done separately with:

debmans -o html render --srcdir manpages

This is especially important if the extraction process was interrupted, as only part of the manpages will be rendered on subsequent runs.

Manpages are currently rendered with man2html but this can be changed with the -r flag, although no other renderer has been tested and the output may not be compatible with man2html.

Static pages rendering¶

The templating engine is fairly simple, based on Jinja2, which uses standard {{foo}} placeholders. The template is in static/template.html and should be following debian.org’s graphic design conventions.

This should generate the markdown files:

debmans -o html site

Use --prefix if the directory is not at the root of the host.

Extract¶

This part fetches all manpages from the archive and stores them on disk. This makes them usable for tools like dman that browses remote webpages.

The layout options for where to store files were:

• Ubuntu: $DISTRIB_CODENAME/$LOCALE/man$i/$PAGE.$i.gz (see dman)
• original codebase: "${OUTPUTDIR}/${pooldir}/${packagename}_${version}" (from manpage-extractor.pl)

Ubuntu’s approach was chosen to avoid bitrot and follow more closely the existing filesystem layout. It also happens to be easier to implement.

The extractor uses a cache to avoid re-extracting known manpages. We use the Ubuntu layout there as well ($outputdir/$suite/.cache/$packagename_version), which leads to bitrot, but at least it’s constrained to a suite. This will be a problem for unstable, so maybe some garbage-collection may be necessary.

Render¶

This converts manpages to HTML so they are readable in a web browser.

Possile options for this implementation:

• just the plaintext output of man wrapped in <PRE> tags (current design)
• man2html is an old C program that ships with a bunch of CGI scripts
• there’s another man2html that is a perl script, but I couldn’t figure out how to use it correctly.
• w3m has another Perl script that is used by the Ubuntu site
• roffit is another perl script. the version in Debian is ancient (2012) and doesn’t display the man(1) synopsis correctly (newer versions from github also fail)
• pandoc can’t, unfortunately, read manpages (only write)
• man itself can generate an HTML version with man -Hcat man and the output is fairly decent, although there is no cross-referencing

The Makefile here tests possible manpage HTML renderers. Each is timed with time(1) to show its performance.

Here is how the actual output compares:

man2html was originally chosen because it is the fastest, includes an index and is not too opiniated about how the output is formatted. Unfortunately, it would fail to parse a lot of manpages, like the ones from the gnutls project. w3m was used as a fallback, even though it actually calls man itself to do part of the rendering.

Index¶

This indexes HTML pages in a search engine of some sort.

In the backend, something will need to index the manpages if only to implement apropos(1) functionality, but eventually also full-text search. This should be modular so that new backends can be implemented as needed.

For now, we are considering reusing the existing Xapian infrastructure the Debian project already has.

The indexer would:

1. run omindex on the HTML tree and create a database
2. process each locale separately so they are isolated (may be tricky for LANG=C) and that the right stemmer is called
3. need a CGI script (provided by the xapian-omega package) to query the database - the HTML output is generated based on templates, so presumably we could reuse the existing templates.

It is assumed that Xapian can deal with large datasets (10-50GB) considering how it is used in Notmuch (my own mailbox is around ~6GB) and lists.debian.org.

We put the command name in the page <title> tag, the short description in <meta description="..."> and use the magic markers (<!--htdig_noindex-->ignored<!--/htdig_noindex-->) to make the indexer ignore redundant bits.

See the Search section for more information about the various search software evaluated and the web interface.

$ ominxed --url / --db search --mime-type=gz:ignore html/
11.03user 0.36system 0:12.27elapsed 92%CPU (0avgtext+0avgdata 29952maxresident)k
18056inputs+15688outputs (0major+7884minor)pagefaults 0swaps

$ time omindex --url / --db search --mime-type=gz:ignore html/
0.01user 0.00system 0:00.02elapsed 88%CPU (0avgtext+0avgdata 4656maxresident)k
0inputs+0outputs (0major+300minor)pagefaults 0swaps

$ delve search.db
UUID = 6fd4d4ab-2529-4d67-bbff-32b88fd888fa
number of documents = 452
average document length = 3976.96
document length lower bound = 78
document length upper bound = 243183
highest document id ever used = 452
has positional information = true

$ quest -d search.db man2html | grep ^url
url=/cache/man/fr/man1/man2html.1.html
url=/cache/man/man1/man2html.1.html
url=/cache/man/ro/man1/man2html.1.html
url=/cache/man/it/man1/man2html.1.html
url=/cache/man/el/man1/man2html.1.html
$ quest -d search.db setreg | grep ^url
url=/cache/man/man1/setreg.1.html
url=/cache/man/man1/mozroots.1.html
url=/cache/man/man1/chktrust.1.html
url=/cache/man/man1/certmgr.1.html

Searching¶

The search interface itself would be a CGI or WSGI tool (if written in Python) interface that would hook into the webserver to perform searches.

Currently only a browser-based, Javascript search tool implements basic whatis(1) functionality. It looks up the manpage using a XMLHttpRequest to see if the requested page exists and redirects appropriately. It doesn’t look at different locales yet.

This should be extended to a full search interface, using omega‘s web interface or other pluggable interfaces.

Original manpages.d.o codebase¶

The original codebase is a set of Perl and bash CGI scripts that dynamically generate (and search through) manpages.

The original codebase extracts manpages with dpkg --fsys-tarfile and the tar tar commands. It also creates indexes using man -k for future searches. Manpages are stored in a directory for each package-version pair, so it doesn’t garbage-collect disappeared manpages. It also appears that packages are always extracted, even if they had been parsed before.

The CGI script just calls man and outputs plain text wrapped in <PRE> tags without any cross-referencing or further formatting.

There is also a copy of the Ubuntu scripts in the source code.

dgilman codebase¶

A new codebase written by dgilman is available in github. It is a simple Python script with a sqlite backend. It extracts the tarfile with dpkg --fsys-tarfile then parses it with the Python tarfile library. It uses rather complicated regexes to find manpages and stores various apropos and metadata about manpages in the sqlite database. All manpages are unconditionnally extracted.

Possible optimizations¶

Optimization ideas:

• extract only targeted files from the archive instead of iterating over it? not sure it’s an improvement...
• use os.scandir() where relevant, instead of os.walk() and stat
• use multiprocessor.Pool for background job rendering? maybe by firing up rendering as soon as pages are created
• use md5sums to check if files were modified, edit cii badge when implemented (security section)
• pre-compile all regexes

Those will be implemented as needed, remember:

Premature optimization is the root of all evil. – Donald Knuth

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