Hello, I just downloaded new man pages for GIT on CentOS 6.3 and I've read I need to run mandb to update the index.
However, the command seems to be missing.

I think that Centos uses makewhatis. It can be found in the man package.

http://rpm.pbone.net/index.php3/stat....i686.rpm.html

2 members found this post helpful.

Great, thanks!

A related question: I copied new man pages into /usr/local/shared/man/man1/ directory, while the existing man pages are located in /usr/shared/man/man1/ directory.
Should I just go ahead and replace the old man entries, or keeping them in the local dir is fine? What would be the reason to keep new entries in the local dir (separately from the old entries)?

That's a good question. If you want, just copy the old man pages to somewhere safe and install your new man pages in the old directory. Keep in mind that going around the man page database in this fashion will probably lead to some breakage...

But by keeping the old pages in a safe place you should be able to put them back if things go pear shaped.

Why not leave them where they are?

What do you mean by "going around man page database"? It seemed to me that having various versions of man pages scattered among multiple directories could potentially be bad for the man database.
What does mandb command (makewhatis on CentOS) do exactly?

That's what I meant. Moving the pages around manually might very well break things. So keep a copy and put things back the way they were and nobody has to be the wiser...

It really isn't going to hurt anything, other than you might end up with a system that is so hosed that it makes more sense to re-install than it would to fix it.

So consider yourself forewarned.

But that is (for better or worse) part of many users early linux experiences. It was for me in any case...

You can install man-db for Centos:

http://pkgs.org/download/man-db

As for what mandb does, here is what the man page for it says:

"mandb is used to initialise or manually update index database caches
that are usually maintained by man. The caches contain information
relevant to the current state of the manual page system and the infor‐
mation stored within them is used by the man-db utilities to enhance
their speed and functionality.

When creating or updating an index, mandb will warn of bad ROFF .so
requests, bogus manual page filenames and manual pages from which the
whatis cannot be parsed.

Supplying mandb with an optional colon-delimited path will override the
internal system manual page hierarchy search path, determined from
information found within the man-db configuration file."

So if you like, run mandb while supplying the path to the new location of your man pages. It should work, it what it does.

Thanks!
Does it make sense to install mandb even though makewhatis seems to be doing its job?
If yes, should I install the rpm for the latest Fedora?
What is the difference between mandb and makewhatis?

To your first question, well, of course! How else are you going to find out which one you like better? I am assuming here that this is not a production machine...

To the second, give it a try. see what it complains about (if anything). If all else fails, you can compile it from the source.

To the third, darned if I know.

Keep in mind that when you do this sort of thing, that there was probably a good reason why mandb was depreciated. Like a security hole. It turns out that there was a small one back in 2000. I would assume that it has been patched by now.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=72292

Go for it!