Documentation

Multi-homing a Joomla site between the WWW and a Tor Hidden Service

I did some work recently on making BenTasker.co.uk available via both a Tor Hidden Service (otherwise known as a .onion) and via the WWW.

The reasons for doing this are published elsewhere, but this documentation summarises the steps I had to take (and why) in order to have the site safely accessible via both routes of access.

For those who are interested, there's a far higher level of detail over on Projects.bentasker.co.uk.

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Copying a Linux Kernel From One System to Another

There may be occasions where, for testing purposes, you want to copy a kernel from one machine to another.

There are some fairly self-explanatory caveats:

  • The donor and target system must be running on the same architecture
  • The target machine shouldn't have any (important) hardware that's unsupported by your donor kernel

Obviously, you'll ideally want to make sure that the hardware is as close to identical as possible (otherwise your testing may be invalid) so the above should be considered a minimum

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sar Cheatsheet

sar can be an incredibly helpful utility when examining system performance, but if not used regularly it's easy to forget which flags to use.

This short post details a number of useful arguments to pass

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ls -l Shows Question Marks instead of Permissions

Occasionally, when running ls -l within a directory, you might find that the output shows question marks (?) instead of the usual permissions indicators:

ben@Queeg:~$ ls -l ~/test
ls: cannot access /var/www/html/Vx/Notes: Permission denied
total 0
d????????? ? ? ? ? ? Notes

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Avoiding BCC Leaks with Exim

This issue is, by no means, Joomla specific - but Joomla's mass mail functionality provides a good example of what can go wrong.

The expectation that most users have, is that the list of recipients BCC'd on an email will never be visible to any of those recipients.

Unfortunately, whether or not that's the case may well depend on the Mail Transport Agent (MTA) that you are using.

Those familiar with Joomla's Mass Mail feature will know that by default, recipients are BCC'd - unfortunately, if you're using Exim (which most CPanel servers, for example, are) then you may in fact find that those receiving your message can see exactly who it was sent to.

Whether or not this BCC Leak is visible to the recipients will depend on what mail client they use (assuming they're not in the habit of looking at the mail headers anyway....), but those using Google Apps/Google Mail will have the list clearly presented to them when viewing the mail.

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