Archive | November 2013

Smartmontools – How does a failure look?

There are some things that you would rather not find out for yourself. That does not mean, however, that they are not useful to see at all. One of those things that I had wondered about was how harddisk SMART failures/errors are shown. For those who are familiar with Smartmontools know that smartctl can produce quite some information when started as:

smartctl –all /dev/sda

However, there’s this handy switch ‘-H‘ (i.e. “smartctl -H /dev/sda“) which supposedly shows you its health status. Now when everything is fine, the disk’s health is reported as ‘PASSED‘. This is nice, but the PASSED case isn’t particularly interesting. What does it look like, when it is not ‘PASSing’? Well, then it looks like this:

smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.2.0-4-amd64] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: FAILED!
Drive failure expected in less than 24 hours. SAVE ALL DATA.
Failed Attributes:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
5 Reallocated_Sector_Ct   0x0033   129   129   140    Pre-fail  Always   FAILING_NOW 561

Now, I have to say that this wasn’t anything unexpected. After all, the PC was suffering from continuous read errors yesterday. But, it is good to know that there is something serious going on, instead of some random unexplained anomaly, which is definitely confirmed by above message and failure details. It does not mean that the details are perfectly accurate, however if you love your data, it’s better to err on the side of caution. Especially given subtle hints like these.

Running Debian Testing (a.k.a. Jessie)

Debian is known for its rock solid, stable releases. Unfortunately these releases tend to contain packages that are somewhat dated, because they have been stabilised for a while before they were finally added and Debian is released. This can be somewhat frustrating.

Recently “rolling release” distributions have become more popular. I believe that this is in large part due to ArchLinux, which is a popular rolling release distribution. ArchLinux is a fine distribution, but it tends to be somewhat low level. Installation for example is limited to (text mode) terminal commands. A good learning experience for sure, but not for everyone.

Another option is to use Debian Testing.”Testing” is now what is going to be the next release of Debian once it has stabilised.”Testing” contains newer packages than the current release and depending on the type of application this often means the newest release.When the freeze happens,”Testing” will stop including new packages in order to stabilize to become the next release. The stabilization period is supposed to be short, although this is not always the case. You can help with this by running testing and reporting bugs as you find them.

After the release has happened you can decide to keep using the current release, as the package manager is often configured to get packages based on the name of the release which by then has officially been released. Or you can change this to ‘testing’ to keep yourself on “Testing” indefinitely.

My experience thusfar is that even Debian Testing is pretty stable. I have not had a serious breakdown in quite a while, although I have temporarily had a program that segfaulted. This was quickly fixed however. As you understand you should not do this on a computer that is of critical importance. Basically, if you require this computer to work at all times, don’t take the chance.

Debian Testing contains packages that have “soaked” for a few days in unstable. If within that time problems are detected, the package will not be promoted to Testing. This helps to ensure that you do not get caught by biggest/baddest mistakes. If this is enough insurance for you and you want Debian with newer packages than what is currently available in Debian Stable, give it a try!

Also: Start updates with ‘apt-get -u upgrade‘ in order to: 1. see what’s being offered, and 2. prevent accidentally deleting packages that get removed due to missing dependencies. Do ‘apt-get -u dist-upgrade‘ once in a while when you have some time to carefully check wat is being proposed. ‘dist-upgrade‘ is more enthusiastic and will remove packages if required.