Becoming A CTAN Mirror

Having a .. CTAN mirror will change your life. – M Doob

You can help out the TeX community by running a mirror of the Comprehensive TeX Archive Network. This page contains directions on how to become an official CTAN mirror. They should suffice if you run Linux and probably also if you run Macintosh OS X. (If you write up instructions for a Windows system, please, let us know.)

CTAN has three core sites, which install new packages and package updates. There are also a fair number of sites that participate as mirrors, who copy our holdings every night and then makes those files available to others in the TeX community. At the core sites we redirect requests for file downloads to our mirrors, thereby reducing the load on the primary three sites. We do this by sending users to web addresses beginning with mirror.ctan.org, which sends the user to a randomly-selected official mirror in their region.

If you decide to become a mirror then once you have it set up, it mostly runs itself. So this is a low-impact way to help out. You need a permanent IP address and at least 20 GB of hard drive space free (30 GB leaves room to grow). The traffic is not too much, but if we have enough mirrors then of course each of them helping a little results in an overall help that is big.

These are the steps to setting up a mirror. More on each is in a section below.

• Giving visitors access to files means running either a web or FTP demon, or both.
• Get the files to hold from us by running rsync.
• Update those files every day. This means running rsync as a cron job.
• Sign up to be an official mirror.

Simplicity

The two most popular way to offer the files to your visitors are over HTTP and over FTP. To keep the discussion straightforward, the examples below assume that you keep the archive in the /var/ftp/pub/tex-archive directory.

If you will offer the materials over HTTP then you must have a web server. We use Apache. Setting up the web server is beyond this document's scope. However, here are a few suggestions to consider.

• One way to make the archive available is by putting a soft link inside your document root. With the default Apache setup, this

    ln -s /var/ftp/pub/tex-archive /var/www/html/tex-archive
  

  makes http://www.example.com/tex-archive give the page showing the top level directory for the archive.

• You want to keep files in the archive that happen to be named index.html from being served by your Apache as the index of that directory's page. Put something like this in your configuration file.

  <Directory />  # prevent web visitors from seeing outside the web tree
    Order Deny, Allow
    Deny from all
  <Directory>
  <Directory /var/www/html>  # allow web visitors to see in the web tree
    Order Allow, Deny
    Allow from all
    Options +FollowSymLinks
  </Directory>
  <Directory /var/www/html/tex-archive> # soft link to CTAN tree
    Order Allow, Deny
    Allow from all
    Options -ExecCGI, +FollowSymLinks, -Includes, -IncludesNOEXEC, +Indexes
    DirectoryIndex      # no value, so 'index.html' is not used
  </Directory>
  

To offer materials over FTP, you must have an FTP demon running. We use ProFTPD but there are many others. Setting up the demon is beyond our scope, but if your documentation does not cover how to allow anonymous access then just get new server software.

Synchronicity

To keep your materials up to date run rsync. This program does the transfers efficently, saving both us and you a great deal of network traffic.

You must mirror from one of these three primary CTAN nodes. The example below uses the first but you should pick the one nearest to you.

The command below will get everything on CTAN and put it on your hard drive. Use it the first time you get from the archive, and also for later updates. Note that the first time you run it the command can take quite a long time — hours, perhaps, depending on the connection speed.

  rsync -av --delete rsync://rsync.cam.ctan.org/CTAN /var/ftp/pub/tex-archive

A summary of what the options mean:

• -a puts you in archive mode so that you look through directories recursively, preserve timestamps, etc.
• -v is for verbose output that reports the files downloaded and deleted
• --delete will delete files that used to be on CTAN but are no longer there.

Before you run the above command, you can check that you will get the result that you expect by using the -n option, as in rsync -avn --delete ... This will say what would be done without doing it.

Periodicity

You must run the above command every day. At the command line ask for crontab -e and in the editor that appears enter a line like this.

  31 2 * * * rsync -a --delete rsync://rsync.cam.ctan.org/CTAN /var/ftp/pub/tex-archive

• at 31 minutes past the hour
• of the 2-th hour of the day
• on every day of the month
• and during every month of the year
• and every day of the week (that is, Sunday thru Saturday).

Please change these numbers when you set yours up, so that not everyone in the world hits us at the same instant. Pick a time that is in the middle of the night at the location of the archive that you are mirroring.

Authenticity

When you have the files, and the cron job working, and have checked that you are offering public access, sign up to become an official mirror.

Note: we monitor mirrors to check that they are up to date. If your mirror falls behind then mirror.ctan.org will not redirect to it, and we shall have to remove it from the official list.