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Magic entries for BTRFS and Software RAID

I’ve just discovered that the magic database for the file(1) command in Debian/Unstable has no support for Linux Software RAID and that it’s support for BTRFS is lacking (no reporting of space used, number of devices, or the UUID). Below is my first draft of a change to fix these problems. I would appreciate it [...]

How to Start Learning Linux

I was asked for advice on how to start learning Linux. Rather than replying via email I’m writing a blog post for future people who ask such questions and also to get comments from other people which may provide information I missed.

Join a LUG

The best thing to do is to start by joining [...]

Timing Processes

One thing that happens periodically is that I start a process from an interactive shell, discover that it takes longer than expected, and then want to know how long it took. Basically it’s a retrospective need to have run “time whatever” that I discover after the process has been running for long enough that I [...]

Flash, Apple, and Linux

Steve Jobs has published an interesting article about Flash [1]. He criticises Flash for being proprietary, this seems a little hypocritical coming from Apple (who’s the only competitor for Microsoft in terms of being the most proprietary computer company) but is in fact correct. Steve advocates HTML5 which is a better technical solution to a [...]

Marshmallow Challenge for Linux Programmers

Tom Wujec gave an interesting TED talk about training people in team-work and engineering through building the tallest possible structures from 20 pieces of spaghetti, 1 yard of string, and 1 yard of sticky-tape with a time limit of 18 minutes [1]. The project is completed by groups of four people – which is probably [...]

Discovering OS Bugs and Using Snapshots

I’m running Debian/Unstable on an EeePC 701, I’ve got an SD card for /home etc but the root filesystem is on the internal 4G flash storage which doesn’t have much spare space (I’ve got a full software development environment, GCC, debuggers, etc as well as running KDE4). On some of my systems I’ve started the [...]

Ext4 and Debian/Lenny

I want to use the Ext4 filesystem on Xen DomUs. The reason for this is that the problem of fsck times on ext4 (as described in my previous post about Ext4 [1]) is compounded if you have multiple DomUs running fsck at the same time.

One issue that makes this difficult is the fact that [...]

Ext4 and RHEL5/CentOS5

I have just noticed that Red Hat added Ext4 support to RHEL-5 in kernel 2.6.18-110.el5. They also added a new package named e4fsprogs (a break from the e2fsprogs name that has been used for so long). Hopefully they will use a single package for utilities for Ext2/3/4 filesystems in RHEL-6 and not continue this package [...]

The Transition to Ext4

I’ve been investigating the Ext4 filesystem [1].

The main factor that is driving me to Ext4 at the moment is fsck times. I have some systems running Ext3 on large filesystems which I need to extend. In most cases Ext3 filesystems have large numbers of Inodes free because the relationship between the number of Inodes [...]

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 [...]