Tag: tech

Valgrind/Helgrind and STL string

I am trying to track down a thread-safety problem in one of my programs. Valgrind when run as “valgrind –tool=helgrind ./thread-test” claims that there is a problem with the following program (the Valgrind errors are at the end of the post). The SGI documents state [1]: “The SGI implementation of STL is thread-safe only in […]

Misc Computer

Finding Thread-unsafe Code

One problem that I have had on a number of occasions when developing Unix software is libraries that use non-reentrant code which are called from threaded programs. For example if a function such as strtok() is used which is implemented with a static variable to allow subsequent calls to operate on the same string then […]


Google Server Design

Cnet has an article on the design of the Google servers [1]. It seems that their main servers are 2RU systems with a custom Gigabyte motherboard that takes only 12V DC input. The PSUs provide 12V DC and each system has a 12V battery backup to keep things running before a generator starts in the […]

Misc Computer

Choosing a Server for CPU Intensive work

A client is considering some options for serious deployment of some CPU intensive work. The options that are being considered include cloud computing (Amazon EC2 [1]), virtual machines (Slicehost [2] and Linode [3]), and purchasing servers to install in racks at various locations. I can’t disclose the criteria that will determine when each of those […]

Misc Computer

Question about a “Secure Filesystem”

I have just been asked for advice about “secure filesystem” and decided to blog my answers. The first issue is what is meant by “secure filesystem, that could either mean the ability to restrict file access (EG by supporting SE Linux security contexts and using SE Linux for file access control) or the ability to […]


Why Cyrus Sucks

I’m in the middle of migrating a mail server away from the Cyrus mail store [1]. Cyrus provides a POP and IMAP server, a local delivery agent (accepting mail via LMTP). It is widely believed that Cyrus will give better performance than other mail stores, but according to a review by linux-magazin.de Dovecot and Courier […]


Maildrop, IMAP, and Postfixadmin

I have recently configured my mail server to use IMAP. I started doing this when I was attending Linux.conf.au so that I could read urgent mail using my EeePC while at the conference and then be able to deal with the more complex stuff using my laptop later on. The next logical step is to […]

Linux.conf.au Mta

SE Linux Lenny Status Update

I previously described four levels of SE Linux support on the desktop [1]. Last night I updated my APT repository of SE Linux packages for Lenny (as described on my document about installing SE Linux [2]). I included a new policy package that supports logging in to a graphical session via gdm in either unconfined_t […]


Netbook Thermal Issues

Recently there has been increasing attention paid to thermal issues. The power used by computers not only impacts the electricity bill (and battery life for a portable device) but is a cooling problem. The waste heat from desktop systems and servers costs energy (and therefore money) to remove by the air-conditioning system and the heat […]

Misc Computer


On Tuesday afternoon I gave a talk on behalf of KaiGai Kohei about SE Linux and the LAPP (Linux Apache, PostgreSQL, PHP/Perl) stack. KaiGai has blogged about this [1], unfortunately Google Translation does a poor job of Japanese and has particular problems with KaiGai’s work (could anyone who knows Japanese and English well please submit […]