How to enable and disable serial ports on Ubuntu
Today, I had to fix a bug in some software I’m working on. The details of the bug aren’t that important, apart from the fact that the bug only became apparent when the software was run on a system with one or less serial ports.
Since I’m debugging on Ubuntu, and I have two serial ports (/dev/ttyS0 and /dev/ttyS1), I needed to find a way to temporarily disable one. This is how I achieved it.
As I’ve mentioned before, I run Ubuntu on an AMD64 processor. I was recently surprised to see that running the new release of Eclipse (Europa) was causing me issues. Basically, Java (or the native parts of these projects) was throwing a wobbly when trying to run 32-bit code on a 64-bit JVM. I thought the goal of Java was write once, run anywhere!
It took me a while, but I managed to find a 64-bit install of Europa. You have to take the “Eclipse Classic” SDK version for Linux x86_64. This installed and ran using the default instructions provided (unzip and run).
Netbeans 6.0M9 gave me similar issues a while back. I never got around to fixing it, but I noticed yesterday that 6.0M10 has been released. This installed and ran straight away. I guess they’ve included x86_64 support in the installer now.
I got no excuses for not developing something useful now :-)
While this affected me on Ubuntu, I guess it’s possible that other Linux distros will also be affected. Though the incorrect use of usermod, I managed to screw up my groups configuration leaving me without sudo or su ability, which is obviously important on Ubuntu to make system configuration changes. Read on for the whole story of how I recovered, and restored correct groups again.
History of SQL
In 1970 Dr. E. F. Codd published his paper,“A Relational Model of Data for Large Shared Data Banks”. This became the foundation for the relation database system. This paper described a new way to structure data within a database, and led to the relational database systems we use today. Continue reading