etbe

20 Nov

Conditions of Sending Email

Update: Due to the popularity of this post I have created a T-Shirt and put it on sale at http://www.cafepress.com/email_eula .
Update: Unlike most of my blog content I permit anyone to copy most or all of this post for commercial use (this includes blogs with google advertising) as long as they correctly identify me [...]

18 Nov

Better Social Networking

When advogato.org was still cool I signed up to it. It was an interesting research project in skill metrics (determining the rating of people’s coding skills by the votes of others and weighting the votes by the rating of each person), and it was nice to be rated Master soon after I joined. [...]

16 Nov

Software vs Hardware RAID

Should you use software or hardware RAID? Many people claim that Hardware RAID is needed for performance (which can be true) but then claim that it’s because of the CPU use of the RAID calculations.
Here is the data logged by the Linux kernel then the RAID-5 and RAID-6 drivers are loaded on a 1GHz [...]

14 Nov

More About Living in Hotels

In the past I have spent about 18 months living in hotels with a couple of months of breaks in between. I have previously written about it in terms of living in London hotels [1], but I have been asked for more generic advice.
Firstly the amount of possessions that you may have when living [...]

13 Nov

Restorecon Equivalent for Unix Permissions

SE Linux has a utility named restorecon to set (or reset) the security context. This is useful for many reasons, corrupted filesystems, users removing files or changing the context in inappropriate ways, and for re-creating files from tar files or backup programs that don’t restore SE Linux contexts. It can also be used [...]

07 Nov

Xen for Training

I’m setting up a training environment based on Xen. The configuration will probably be of use to some people so I’m including it below the fold. Please let me know if you have any ideas for improvements.
The interface for the user has the following documentation:

sudo -u root xen-manage create centos|debian [permissive]
Create an image, [...]

06 Nov

Squid and SE Linux

Is Squid not returning some data you need on a SE Linux system?
The default configuration of the SE Linux policy for Squid only allows it to connect to a small number of ports which are used for web servers. For example ports http (80) and https (443) are labelled as http_port_t which permits serves [...]

02 Nov

Increasing Efficiency through Less Work

I have just read an interesting article titled Why Crunch Mode Doesn’t Work [1] which documents the research on efficiency vs amount of time spent working (and by inference amount of time spent on leisure activities and sleep). It shows that a 40 hour working week was chosen by people who run factories (such [...]

01 Nov

Load Average

Other Unix systems apparently calculate the load average differently to Linux. According to the Wikipedia page about Load(computing) [1] most Unix systems calculate it based on the average number of processes that are using a CPU or available for scheduling on a CPU while Linux also includes the count of processes that are blocked [...]

28 Oct

Xen and Security

I have previously posted about the difference between using a chroot and using SE Linux [1].
Theo de Raadt claims that virtualisation does not provide security benefits [2] based on the idea that the Xen hypervisor may have security related bugs.
From my understanding of Xen a successful exploit of a Xen system with a Dom0 that [...]

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