Wednesday, August 24, 2011

Rsync - What on earth did I do!

I created a new document related to a course I am teaching on my netbook. I rsync'd my netbook to the desktop. To my horror, the lecture notes I had prepared on the desktop were over-written by the version on the netbook.

Why can't software prevent me from doing something so dumb.

Well, I should have examined the implications more carefully for bi-directional rsync.

Another often used flag not included in -a is -u, which says not to overwrite newer files. If we wanted to do a Briefcase style synchronization, we need -u, and we need to do the rsync in two directions:
rsync -aHu a/* b
rsync -aHu b/* a

Monday, August 22, 2011

Arch Linux - experience with kernel 3.0

Upgrading to kernel 3.0 on Lenovo S10-3 did have a couple of issues. The first issue was that the wifi was not functioning. This was easily solved by following the instruction on Arch Wiki and blacklisting the conflicting bcma driver.

The other issue was that waking from sleep is not working any more. This is in spite of  adding 'intel_idle.max_cstate=0' to the kernel boot options. Hence, I reverted to kernel 2.6.39 until I have time to examine the problem in more detail and see if  there is a workaround.

Incidentally, I have been facing erratic behaviour with waking from sleep on Lenovo S10-3 with Ubuntu 11.4 with 2.6.38 kernel and Fedora 15 with 2.6.40(!) kernel. I thought that the reason may be that I am using x64 versions of Ubuntu and Fedora whereas on Arch Linux I have installed the i386 version.

Update: A silly mistake in Fedora 15 grub.conf file. I had typed 'state' instead of 'cstate'. Initial tests of sleep work on Fedora 15 with kernel 2.6.38 but not with 2.6.40 (presumably the same as mainline 3.0). I will have to check if the behaviour of waking from sleep on Fedora is consistent as on Arch Linux or erratic as on Ubuntu.

Update 2 -  I found that there is a bug report of the waking from sleep issue on Debian bugs list when upgrading from 2.6 to 3.0.

Retraction of Farewell to Education

About 5 years ago, I had given up on education in India. From August, I started to teach a course - Software Engineering. The difference is that it is at IIT, Ropar, instead of a college affiliated to a university.

After two weeks, I was wondering what makes the difference to me. I am sure the students are very good; however, I had enough good students that that was never a de-motivational issue.

The major impact for me is the control over the course. I am experimenting with a lab - I may be wrong but I think it is worth trying and seeing if the students learn more. The fact that the lab grade matters, the students are willing to be a part of my experiment. I just have to convince them that the experiment will not be unfair to any.

I suddenly realised that I was covering more content than I expected. I can choose to leave out parts I do not think are very important today and add content related to agile processes which appeals to me a lot more. I can also choose to emphasise tools which I believe help create better software. I do not have to worry about the paper setter or complaints of 'out of syllabus' from students of another college.

Bottom line - I am enjoying it and enjoying the effort I have to put into fine tuning the course to hopefully make it more effective.