Category: Linux

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 […]

Linux

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 […]

Linux

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 […]

Linux

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 […]

Linux

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 […]

Linux

Per-process Namespaces – pam-namespace

Mike writes about his work in using namespaces on Linux [1]. In 2006 I presented a paper titled “Polyinstantiation of directories in an SE Linux system” about this at the SAGE-AU conference [2]. Newer versions of the code in question has been included in Debian/Lenny. So if you want to use namespaces for a login […]

Linux Security

Things you can do for your LUG

A Linux Users Group like most volunteer organisations will often have a small portion of the membership making most of the contributions. I believe that every LUG has many people who would like to contribute but don’t know how, here are some suggestions for what you can do. Firstly offer talks. Many people seem to […]

Linux

Debugging as a Demonstration Sport

I was watching So You Think You Can Dance [1] and thinking about the benefits that it provides to the dancing industry. The increase in public appreciation for the sport will increase the amount of money that is available to professionals, and getting more people interested in dancing as a profession will increase the level […]

Linux

Swapping to a Floppy Disk

In the mid 90’s I was part-owner of a small ISP. We had given out Trumpet Winsock [1] to a large number of customers and couldn’t convert them to anything else. Unfortunately a new release of the Linux kernel (from memory I think it was 2.0) happened to not work with Trumpet Winsock. Not wanting […]

Linux

A Basic IPVS Configuration

I have just configured IPVS on a Xen server for load balancing between multiple virtual hosts. The benefit is not load balancing but management. With two virtual machines providing a service I can gracefully shut one down for maintenance and have the other take the load. When there are two machines providing a service a […]

Ha Linux