"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects." (Robert A. Heinlein)

Friday, 27 May 2016

Upgrading (the EEEPC) with low disk space

When, while installing Xubuntu, I decided EEEPC disk partitioning I based my decision on previous installation typical disk usage worrying mostly about “/home” and “/usr” partitions. I never would have thought about running out of space in the root “/” partition.
Then, the first time I tried to upgrade to latest Xubuntu distribution I got an error message about disk free space on partition being not enough to download distribution files (that usually take a little less than 1GB of disk space). Examining disk free space I discovered that very little free space was left on the root partition even if it was more then enough after my post-installation check.
Fortunately AskUbuntu came quickly at recover: here I quickly found a question asked from who had the same problem. To be precise the question was about problems with “/boot” partition low disk space bat I suppose it was because of a different partitioning schema, by the way solution worked for me.

Cleaning “apt-get” leftovers

As I learned from AskUbuntu question some of the “lost” disk space might be occupied by unused files or apt-get temporary files. So simply by executing the following commands …
sudo apt-get autoremove
sudo apt-get clean
some disk space can be set free.

Removing old Linux kernel images

If free space gained from the previous operation isn't enough some more space can be obtained by removing old Linux kernel images. Every time Ubuntu upgrade to e new kernel release the old one is kept available in to be used to solve possible compatibility issues. Such feature is scarcely user and is of no use at all in the eve of a major distribution upgrade.
First the currently used Linux kernel must be identified the command …
uname -a
does the job, here is the current output
Linux eeepc900 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:34:49 UTC 2016 i686 i686 i686 GNU/Linux
while the command …
dpkg -l 'linux-image*'
lists all Linux kernel images currently installed, here is a sample output:
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
un linux-image <none> <none> (no description available)
un linux-image-3. <none> <none> (no description available)
rc linux-image-3. 3.19.0-15.15 i386 Linux kernel image for version 3.
rc linux-image-3. 3.19.0-28.30 i386 Linux kernel image for version 3.
rc linux-image-3. 3.19.0-33.38 i386 Linux kernel image for version 3.
rc linux-image-3. 3.19.0-43.49 i386 Linux kernel image for version 3.
ii linux-image-3. 3.19.0-56.62 i386 Linux kernel image for version 3.
ii linux-image-4. 4.2.0-34.39 i386 Linux kernel image for version 4.
ii linux-image-4. 4.4.0-21.37 i386 Linux kernel image for version 4.
rc linux-image-ex 3.19.0-15.15 i386 Linux kernel extra modules for ve
rc linux-image-ex 3.19.0-28.30 i386 Linux kernel extra modules for ve
rc linux-image-ex 3.19.0-33.38 i386 Linux kernel extra modules for ve
rc linux-image-ex 3.19.0-43.49 i386 Linux kernel extra modules for ve
ii linux-image-ex 3.19.0-56.62 i386 Linux kernel extra modules for ve
ii linux-image-ex 4.2.0-34.39 i386 Linux kernel extra modules for ve
ii linux-image-ex 4.4.0-21.37 i386 Linux kernel extra modules for ve
ii linux-image-ge i386 Generic Linux kernel image
eventually older kernel images can be removed with an “apt-get” command like the following, changing of course the version number
sudo apt-get -y purge linux-image-x.yy.z-tt-generic linux-image-extra-x.yy.z-tt-generic linux-headers-x.yy.z-tt linux-headers-x.yy.z-tt-generic
If you look deeper in AskUbuntu answer you'll see that more complex scripts can be used to make the operation faster. I stopped here, I don't like automating too much when deleting things and, after all, this it's I problem I get into at most twice a year. So … I can do it manually

Wednesday, 4 May 2016

Place the Raspberry PI at the centre of your network

My recent problems with Internet providers, followed by the need to change my ADSL modem-router made me think if it would be wiser to make my home network less router dependent. Local network at my home, like most home networks, relies on the ADSL modem-router for the Dynamic Host Configuration (DHCP). Every time I changed the router I had so to reconfigure its DHCP server in order to restore my network configuration, often not being able to access to some network devices, like the NAS disk, until the DHCP was properly configured.
While looking for a Raspberry DHCP configuration how-to I literally stumbled into this page about using the Raspberry PI as a wireless router. This also inspired me about using the Raspberry also to provide a backup or private WI-FI access.
Hardware set-up
First things first: I already had a Wi-Fi dongle wandering in my drawers, I installed in the Raspberry PI USB port and checked it worked. Not all the wireless interfaces are able to be used in “access point mode”, to check if the one I had was compatible I installed the “iw” utility:
sudo apt-get install iw
executing the command:
iw list
I got a detailed list of the network interface features, among them in the the supported interfaces modes:
Supported interface modes:
* managed
* AP
* monitor
* mesh point
i got confirm that the interface could work as access point.