Keeping it up to date (given up with the Pi puns)

August 9th, 2012

Continuing from here

First page here

7.  Updating your system

We’ve just got a spot of housekeeping to do before installing some stuff to turn your pi into something useful.  We are going to do a system update to make sure we are running the latest version of everything.  And I mean everything.  The update will not only update the operating system, but all your installed software.  All your Pi’s software comes from a “repository” on the internet of pre-compiled software packages, created by the people who made the Raspbian distribution – over 35,000 packages in total, covering pretty much anything you might want your Pi to do: web server, media server, media streamer, torrent client, DNS, web browser (yes, a text only web browser) and so on.  Each package contains software, configuration files, manual pages, and scripts needed to set the software up after install.  You can install packages from outside the repository or compile your own software, but that is a bit more advanced and everything we need is included in the Raspbian repository.

Software is maintained on a your Pi’s Debian-based Linux system, Raspbian, with a set of utilities called Apt, which is short for “Advanced Package Tool”.  It keeps a track of all the installed software packages, what version they are, if they need updating, and other packages required by each package.  That last one is important.  Most packages will rely on other packages being installed on your Pi in order to work.  From a programmer’s point of view, there is no point in re-inventing the wheel if you want a feature in your program (let’s call your program “Program A”) that has already been created by someone else in Program B.  The programmer can tell program A to call up Program B when this feature is needed.  Then, when the repository maintainer creates Program A’s package for the Raspbian repository, the maintainer adds a specification to the package that tells Apt to check that the package containing Program B is already installed on the Pi.  If it is then that’s fine and dandy, but if it’s not, Apt will nip off and download Program B’s package too.  Of course, it then has to check if the Program B’s package needs any other packages to be installed on the Pi, download them if they aren’t installed, check those ones…, and so on until all the packages are happy.  Keeping track of all these interlinking packages, each depending on the other (package B is called a “dependency” of package A), would be a nightmare to do yourself, so thank goodness for Apt, which does it all for you.

You might think that it sounds a bit complicated, but it’s not.  You will soon see how easy it all is to use.  Then you might start feeling sorry for Windows users and the pain they have to go through – finding the software, downloading it (Windows downloads are usually bigger as they don’t have Linux’s dependency system), going through the install procedure and then finding that the installer just splatted a load of crapware all over their PC.  Do not pity them though.  They have chosen their path.  It’s quite similar (and predates by many years) the “App” system used by Apple, Android etc., except it is far more flexible and doesn’t restrict you to one source of packages.

But back to the updating… Let’s start off by getting a list of software that needs updating.  Type sudo apt-get update and you should see something like this:

naich@raspberrypi ~ $ sudo apt-get update 
Get:1 http://mirrordirector.raspbian.org wheezy InRelease [12.5 kB] 
Get:2 http://archive.raspberrypi.org wheezy InRelease [7,698 B] 
Get:3 http://mirrordirector.raspbian.org wheezy/main armhf Packages [7,296 kB] 
... and so on for a bit... 
Ign http://mirrordirector.raspbian.org wheezy/rpi Translation-en 
Fetched 7,388 kB in 48s (151 kB/s) 
Reading package lists... Done 
naich@raspberrypi ~ $

Lovely jubbly.  It’s got a list of all the latest packages.  Let’s process all the packages that need upgrading to a later version.  Type sudo apt-get upgrade:

naich@raspberrypi ~ $ sudo apt-get upgrade 
Reading package lists... Done 
Building dependency tree Reading state information... Done 

The following packages will be upgraded: 
bash dictionaries-common file idle3 krb5-locales libgssapi-krb5-2 
libk5crypto3 libkrb5-3 libkrb5support0 liblapack3 liblapack3gf 
libmagic1 libpulse0 libsystemd-login0 libtiff4 libxapian-dev libxapian22 
libxml2 libxml2-dev libxslt1-dev libxslt1.1 nfs-common omxplayer 
python3 python3-minimal tasksel tasksel-data udisks vim-common vim-tiny 
xserver-common xserver-xorg-core 

32 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 
Need to get 23.0 MB of archives. 
After this operation, 1,183 kB of additional disk space will be used. 
Do you want to continue [Y/n]?

Do you want to continue?  You do.  And away it goes, upgrading it’s little silicon heart out.  Very rarely, you might see something like this:

Configuration file `/etc/skel/.bashrc'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
 What would you like to do about it ? Your options are:
 Y or I : install the package maintainer's version
 N or O : keep your currently-installed version
 D : show the differences between the versions
 Z : start a shell to examine the situation
 The default action is to keep your current version.
*** .bashrc (Y/I/N/O/D/Z) [default=N] ?

This means that Apt has found a configuration file that been changed since the package was installed.  Unless you have made the change yourself, it’s safest to choose “Y” to install the new version which will be compatible with the updated software. A backup of the old config file will be saved in case the new one doesn’t work so you can examine them later to see the differences and fix them if necessary.

Warnings can generally be ignored.  Things like this probably don’t mean much to you:

insserv: warning: current start runlevel(s) (empty) of script `nfs-common' overwrites defaults (2 3 4 5 S).
insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6 S) of script `nfs-common' overwrites defaults (0 1 6).

And to be honest it doesn’t mean that much to me either.  It looks like it’s saying that the nfs server isn’t automatically started on runlevels 2-5 any more.  Possibly.  We aren’t using nfs so we don’t care; we’ll cross that bridge if we come to it.  My Pi seemed to work OK after those warnings, so I didn’t worry about them.  Make a note of warnings, just in case you need to find a problem later, but don’t worry about them unduly.  “warning: ” means something unexpected has happened but Apt can keep going.  Errors, however, can’t be ignored.  “error: ” means something so bad has happened that Apt can’t continue.  If you ever see an error, the best thing to do is to copy and paste it into Google to find someone else who has had the same problem and has hopefully fixed it.

You want to go through this procedure (“apt-get update” followed by “apt-get upgrade”) every now and again to make sure your system is up to date.  Most updates are due to bugs regarding security and are closing avenues of attack for hackers, so you want to install them.  I do it about once a week.

There is also another type of upgrade – apt-get dist-upgrade. This upgrades your system to the latest stable release.  This means that it won’t just upgrade your packages for bug fixes and security patches, it will upgrade all your software to the version included in the current stable release of your distribution, as if you downloaded and installed it from scratch.  This is a more serious upgrade and should only be undertaken if you’ve got a bit of spare time to fix anything that might get broken.  You are likely to see those messages about the configuration files and might have to edit upgraded ones to get things working again.  If you start seeing messages during your “apt-get upgrade” that packages have been “held back”, it means that you should probably start thinking about doing a “dist-upgrade”.

Continued here…

Another pi pun

July 30th, 2012

Continued from here

First page here.

6.  Creating a user

Now you are starting to get to know your Pi, you’ll want to start making it feel more like home.  Unless your name is “Pi” you will want to add yourself as a user.  Type this:

adduser naich

Do I really need to explain that you should replace “naich” with your name?  If you’ve already guessed that and typed it in with your name, you will probably be slightly worried at this point because it will have replied “adduser: Only root may add a user or group to the system.”

“Root” is the name of the account that has full access to the Linux system.  There are many things that only Root can do, and it’s just as well really; one of the things that only root can do is permanently delete the entire filesystem with one command that doesn’t even bring up an “Are you sure?” type question.  As an ordinary user, you can only screw up your own stuff that you put on there, but as root you are a god that can break everything for everyone forever.  This is why we try to avoid being root as much as possible.  Luckily the root password does not actually exist, so you can never log on as root!  Problem solved, except that sometimes we do want to be able to do rooty stuff, like add users.  There is a way to temporarily become root and that way is sudo.  You might remember typing it in earlier.  Sudo executes a command with root privileges and you simply add “sudo” in front of the command you want to run like this: sudo adduser naich:

naich@raspberrypi ~ $ sudo adduser naich
Adding user `naich' ...
Adding new group `naich' (1000) ...
Adding new user `naich' (1000) with group `naich' ...
Creating home directory `/home/naich' ...
Copying files from `/etc/skel' ...
Enter new UNIX password:

Choose a good password for your username but one you will remember.  Write it down if you have to.  Fill in the rest of the details or leave them blank if you want.  You also need to add your new user to the list of people who can use sudo, so type sudo visudo and you should see this:

#
# This file MUST be edited with the 'visudo' command as root.
#
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
#
# See the man page for details on how to write a sudoers file.
#
Defaults        env_reset
Defaults        mail_badpass
Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:$
... and so on ...

“visudo” is the command that allows you to modify the list, “sudo” means you are temporarily granted root’s super powers in order to do so.  What visudo actually does is load a text file into an editor called “nano”.  Once nano has loaded the sudoers list, move the cursor down to where it says

pi  ALL=ALL(ALL) NOPASSWD: ALL

and change “pi” to your new username.  This means “pi” will no longer be able to sudo, but that doesn’t matter because we are going to delete him soon anyway.  To save the changes and exit nano, press CTRL-X.  If you want to exit without saving your changes press N at the prompt, otherwise press Y and then hit return to save it with the suggested name.  You’ll be using nano a bit, as most configuration is done with plain text files.

Once you have got back to the “pi@raspberrypi:~$” prompt, type exit to log out and log back in again as you.

6.1 A Windows diversion

Windows users: this is the part where we sort out the static IP stuff.  Linux users can skip this bit and go to section 6.2.

You now need to edit two files – the /etc/network/interfaces file that you couldn’t edit earlier, and the /boot/cmdline.txt file to take out the stuff you put in earlier.  Type sudo nano /etc/network/interfaces and use the text editor (in the same manner as you did to edit the sudoers file) to edit the file as described in section 3 (click to open in a new window/tab).  Save it with CTRL-X, [Y]es, Enter and then type sudo nano /boot/cmdline.txt and remove all the text after “rootwait” that you put in earlier.  Make sure the text is still all on one line and that there is still a newline at the end of the line.  Save the file.  Your Pi is now properly configured with a static IP.

6.2 Back to our scheduled programming

Now let’s kill off “pi”.  If you add users with the command “adduser”, you might think you delete them with “deluser”, right?  Nope, it’s userdel.  No idea why.  As a general rule, if you don’t know what command to use, a good place to start is Google – “linux delete user”, returns 205 million pages telling you how to do it.  Anyway, have a go at deleting pi.  I’m not going to tell you how to do it.  See if you can guess.

Done it?  It was sudo userdel pi, by the way.  Do you like the way it didn’t ask if you really wanted to do that?  Linux assumes you know what you are doing and doesn’t treat you like an idiot by asking you if you really want to do something.  Successful operations for simple things (like copying, moving and deleting files, for example), generally won’t produce any output unless you tell them to.

If you don’t know how to navigate the Linux filesystem, now is the time to check out Appendix B and learn all about it.  Got it?  Go to the home directory – cd /home  and have a look – ls :

naich@raspberrypi ~ $ cd /home
naich@raspberrypi /home $ ls
naich  pi
naich@raspberrypi /home $

As well as your new user’s directory, there is also one called “pi”.  Although you deleted the user pi you didn’t delete his stuff.  You don’t need or want it, so get rid of it.  Type sudo rm -r pi (“rm is short for “remove”),… and it’s gone.  As before, there are no prompts, no “are you sure?”s; it’s gone forever.  If this doesn’t make you a little uneasy, then you might not have grasped how devastating a mistake could be and will probably discover this the hard way at some point!

Before you go any further, please consider expanding your knowledge about commands  a bit by reading appendix C.  You don’t have to but it might help you understand what’s going on a bit more.  See if you can find out what the “-r” does when you types sudo rm -r pi earlier.

Continued here…

Appendixes

July 17th, 2012

These are appendixes from the set of posts about setting up and using a Raspberry Pi.

Appendix A: Selecting an IP Address

As part of the boot process, your Pi used DHCP to get an IP address from the router. The problem with this is that it is an automated process which is invisible to you unless you log onto your router’s admin page to discover it.  If only the Pi and your router know what its IP address is, you don’t know where to log on to your Pi.  The easiest thing to do is change the IP settings on the Pi’s card to a static address, assigned by you.  That way you know what it is and you know it won’t change.  You don’t need to let the router know which address you have chosen, as the magic IPixies in the Pi sprinkle the router with their Ipixie Dust to let it know automatically.  Well, they do for all I know; I’ve no idea how the router finds out, but it does.

You need to pick an address for your Pi – something like 192.168.1.16, but you want to pick one that is not in the range of addresses your router assigns for DHCP requests.  If the address you choose is within the router’s DHCP address range there is a possibility that you will end up with two devices using the same address.

I’m going to leave it to you to find out what range of addresses your router assigns for DHCP and which ones are suitable for static IP addresses.  The settings will be available somewhere in your router’s admin pages.  If fiddling around with your router is out of the question, as a quick bodge you could try finding the IP address of your PC in order to guess a safe non-DHCP range address for your Pi.  Copy the first 3 sets of numbers of your PC’s address and change the last number to a low one if it’s not low or a high one (maximum 254) if it is low.  e.g.

  • Your PC’s IP is 192.168.1.3 so you pick 192.168.1.250 for your Pi
  • Your PC’s IP is 192.168.1.101 so you pick 192.168.1.3 for your Pi

You also need to know the gateway (the router’s IP address on the LAN) and subnet mask (which will probably be 255.255.255.0 – it usually is for home networks).

Go back

Appendix B: The Linux Filesystem

Here’s a quick and dirty note about the way the Linux filesystem is arranged.  For a better description try this or this.

You might be used to Windows, with its lame C: drives, D: drives, random assignation of drive letters for plug-in devices, and its pathetic attempts to hide this lameness with My Documents, libraries and other rubbish.  Linux has one hierarchical tree of files, with everything hanging off the root “/” directory.  There are no drive letters or special places; everything – programs, user data, log files, temporary files and even devices, is placed on the same directory tree.  There is a convention as to where different types of file are stored, but let’s have a little wander around and see for ourselves.

Take a look at the command prompt – “naich@raspberrypi ~ $”  It contains 4 pieces of information; your name and the name of the computer you are on (with an “@” between them), the working directory (~) and the effective user ID ($).  The “$” changes to a “#” if you are currently root – that’s all that does, but it is important to know if your powers are currently elevated to those of the godly root.  The working directory is where you currently are in the directory tree, i.e. it is the directory that a command will take action in if you don’t actually specify which directory you want the command to do its stuff in.  Get it?  No?  An example will demonstrate better than that convoluted jumble of words; type ls:

naich@raspberrypi: ~ $ ls
naich@raspberrypi: ~ $

See anything?  Nope.  ls means list all the files in a directory.  As you did not specify a directory it lists the files in the working directory, which is “~”, and is currently empty.  If you tell it to list files in a different directory it will use that one instead of the working one; type ls /:

naich@raspberrypi ~ $ ls /
bin   dev  home  lost+found  mnt  proc  run   selinux  sys  usr
boot  etc  lib   media       opt  root  sbin  srv      tmp  var
naich@raspberrypi ~ $

These are all the files and directories in the root directory “/”.  Try ls /bin – see what is happening there?  You are listing all the files in the “/bin” directory.  This rule also goes for file names.  If you want to access a file but only write a file name, the command or program will look for that file in the working directory.  If you include the directory that the file is in, it will look there instead. This goes for any type of file – data, programs or devices.  Think of your terminal window as psychically sitting on a branch of the directory tree, with everything you type in acting on that branch unless you explicitly specify otherwise.  The location of that branch is the working directory.

Handy hint – Stuff shooting off the top your screen before you can read it?  Add “ | more” to the end of your command, (e.g. ls /bin | more) to show one page of output at a time.  Scroll to the next page with the space bar or press “Q” to quit.  This works with all commands.  Don’t try to understand how it works for the moment, just consider it magic.

You can move your terminal around the directory tree with the cd (change directory) command.  Type cd / to move your working directory to the root directory and type ls again.  Now your working directory is “/”, it lists the files there when you don’t explicitly say otherwise.  Try moving to “/bin” and looking at the files there.  Try moving to other places and have a good old poke around.  Even with a basic install there are tens of thousands of files on your Pi, so there’s plenty to look at.  When you are done, move back to your home directory by simply typing cd ~.

As well as looking at the the prompt, another way to find out the working directory is to type pwd:

naich@raspberrypi ~ $ pwd
/home/naich
naich@raspberrypi ~ $

Eh?  I thought we were in “~”?  Well, we are.  “~” means “my home directory”, which is “/home/your_username”.  Your home directory is where you put all your stuff and is probably the only directory you can write to.  If you are going to start drawing Windows analogies, it is a bit like “My Documents”.  The “~” provides a reference to where all your stuff is, so using “~/README.txt” refers to README.txt which resides in your home directory, rather than any other README.txt which might be in whatever working directory you happen to be in.

It’s all relative though.  When you specify a directory to move to, look in, or to find a file in, the location you give is relative to where you currently are – i.e. your working directory.  If you start the directory location off with a “/” or “~/” it doesn’t matter where you are, as the location you are specifying starts at the root or home directory.  These are fixed absolute points on the tree, but miss off the “/” or “~/” from the start of the directory or file and it becomes relative to your working directory.  Type cd /usr to move your working directory to the “/usr” directory.  Do a ls to see the contents.  See that directory called “bin”?  It’s not the one you looked at earlier; that was a directory for general system bin(ary) programs, this one is for user-orientated bin(ary) programs.  Type ls bin.  The files listed are not the ones you saw earlier in “/bin” but are the ones in “/usr/bin”.  Because the “/” is missing from the front of “bin”, the “bin” it is showing you is the one relative to your working directory, which is currently “/usr”.  You can still see the contents of “/bin” (with the slash) by typing ls /bin (with the slash).

If you understand the concept that everything is relative to the working directory unless you say so, you are ready to know about dots – “..”, “.” and dots at the start of files.

A double dot is shorthand for “the parent directory”, i.e. the next directory down on the way to the root.  If your working directory is “/home/naich” then typing cd .. will change your working directory to “/home”.  Typing ls .. will list the contents of “/home” and so on.  You can string double dots together as if they were real directories. cd ../.. will move you two directories towards root – from “/home/naich” to “/”.  You can do daft things like cd /home/naich/../../home/naich to end up in “/home/naich”, the first “/home/naich” having been rendered pointless by the two sets of double dots moving you back down to “/” again.

A single dot means “this directory”, i.e. the current working directory.  That might not sounds useful, seeing as how, by it’s very nature, you are already working in the working directory but it does have its uses.  I’m not going to go in to them here, but you should know about it in case you see it later on.

Finally, there are hidden files.  These are hidden for convenience not security and are simply files that you don’t care about in the normal scheme of things.  Files like configuration files or log files.  You can hide a file or directory by starting its name with a dot, e.g. “.config_file”.  You have some in your home directory but didn’t see them earlier.  Go home (cd ~) and have a closer look – type ls -a.

naich@raspberrypi ~ $ ls -a
.  ..  .bash_history  .bash_logout  .bashrc  .profile
naich@raspberrypi ~ $

The “-a” bit is an “option” that tells the “ls” command to show hidden files.  Those hidden files are configuration files that are automatically generated when you create a user and control parameters about the way your terminal works.  Most of the time you don’t need to see them, so they are hidden.  You can also see the “.” and “..”, which show up as directories in their own right.

Go back

Appendix C: Commands

The basic format for doing things from the command line has 3 sections separated by spaces:

command [-options] [the_thing_you_are_doing_it_to]

An “option” is a way to modify what the command does.  For example, the default thing for the ls command to do is show the files as a horizontal list, so to list all the files in the root “/” directory:

naich@raspberrypi ~ $ ls /
bin   dev  home  lost+found  mnt  proc  run   selinux  sys  usr
boot  etc  lib   media       opt  root  sbin  srv      tmp  var
naich@raspberrypi / $

but if you add the option “-l” (minus lower case L) to the “ls” command it does this:

naich@raspberrypi ~ $ ls -l /
total 84
drwxr-xr-x  2 root root  4096 Aug  6 12:35 bin
drwxr-xr-x  2 root root 16384 Jan  1  1970 boot
... skip a few ...
drwxr-xr-x 10 root root  4096 Jul 15 19:57 usr
drwxr-xr-x 11 root root  4096 Jul 15 20:42 var
naich@raspberrypi / $

The “-l” means print it in “long” format, i.e. with more information about what sort of file or directory it is (the “d” in “drwxr-xr-x” means directory, don’t worry about the rest for now), who owns it (“root”), the group they are in (root), the size of the file, date it was last modified and its name.  You can have more than one option.  Try ls -lh /.  The “h” means put the file sizes in human readable units.

naich@raspberrypi ~ $ ls -lh /
total 84K
drwxr-xr-x  2 root root 4.0K Aug  6 12:35 bin
drwxr-xr-x  2 root root  16K Jan  1  1970 boot
... and so on

You could make it show you hidden files (“-a”), in date order (“-t”), but reversed so the latest is at the bottom (“-r”) by using ls -lhatr /

naich@raspberrypi ~ $ ls -lahtr /
total 92K
drwxr-xr-x  2 root root  16K Jan  1  1970 boot
dr-xr-xr-x 68 root root    0 Jan  1  1970 proc
drwxr-xr-x 12 root root    0 Jan  1  1970 sys
drwxr-xr-x  2 root root 4.0K Jun  2 10:25 mnt
... etc. ...

Note that the “Jan 1 1970” comes from boot time, when the Pi doesn’t know what time it is (no real time clock), so it defaults to the earliest time a Unix timestamp can have.

It would be pretty unreasonable to expect everyone to remember what all the options are, so most commands have help built in, accessible by using either “-h” or “–help” (that’s two dashes there, compared to the one for single letter options).  With ls, “-h” is used for specifying human-readable units, so –help (with the two dashes) is the option to use for help.

naich@raspberrypi ~ $ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.

Mandatory arguments to long options are mandatory for short options too.
  -a, --all                  do not ignore entries starting with .
... blah blah etc. ...

Options with two dashes and a word are called “long options”, one dash, one letter ones are “short” options.  Obviously you can’t lump long options together behind the same dashes, so you have to use them seperately, i.e. ls --all --human-readable /.  You can also mix them if you want, i.e. ls -la --human-readable /.

A huge amount of help is also available from the manual pages residing on your Pi, which contain more verbose instructions.  You use these by typing “man command”, e.g. man ls or man adduser or even man man.  While they are very detailed and available for pretty much every command you’ll use, a) you need to already know what command you want, and b) they aren’t always written in the clearest manner for a beginner.  Don’t be afraid to google for information too – for example, putting “how do i add a user in linux” into google’s search box gives you exactly what you need to know.  You aren’t born with knowledge of how Linux works so you need to find it somewhere.  Start off with the manual pages but if you only understand a few of the words on them, have a google for it.

Go back

Pi Eyed

June 26th, 2012

Continued from here.

Your Pi is now sitting in the corner of the room, blinking its lights at you and presumably working.  Shall we see if we can do something with it?

3.  Setting up the interweb

Your Pi is working and sitting on the network, waiting for you.  But where is it?  You need to know its address on your network in order to log in, but it will have booted using DHCP, so its address is known only to the Pi and the router.  You need to set up your Pi with a permanent, static IP address of your choosing, as well as a gateway address (the address of the router on the LAN side) and subnet mask.  If you are a bit unsure how to select these, Appendix A might help.

We need to edit a configuration file on the SD card in order to change the settings.  Put your SD card back into your card reader.  What you do next depends on what sort of computer you are using.

If you use Linux on your PC then it’s easy enough – go into the “/etc/network” directory  in the larger partition and edit a file called “interfaces”, as shown below, with a text editor like gedit.  Do not use a word processor such as OpenOffice or LibreOffice.

The /etc/network/interfaces file looks like this:

# Used by ifup(8) and ifdown(8). See the interfaces(5) manpage or
# /usr/share/doc/ifupdown/examples for more information.
auto lo

iface lo inet loopback
iface eth0 inet dhcp

Leave the lines up to “iface eth0…” alone, change that line and add 3 new ones like this:

iface eth0 inet static
address 192.168.1.5
gateway 192.168.1.254
netmask 255.255.255.0

With “address” being the IP address you want to assign your Pi,  “gateway” your gateway and the “netmask” for your home network.  Once you have changed the text and saved the file over the top of the original, safely remove the card, put it in your Pi and reboot.

Unfortunately it’s not that easy for Windows users.  Windows can’t read the Ext3 partition the “interfaces” config file resides in.  This means we have to temporarily force the Pi to use a static IP and then edit the config file on the Pi itself.  Look in the list of files on the card (the 59MB partition) for a file called “cmdline.txt”  Open it up with a text editor – Wordpad is best, do NOT use Word or any sort of word processor.  You will see this:

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait

Make sure that line wrapping is turned off (View->Word wrap->No wrap for Wordpad) and add the text in bold at the end of the line after “rootwait” (with a space between “rootwait” and “ip=192…”:

... rootwait ip=192.168.1.5::192.168.1.254:255.255.255.0::eth0:none

That’s your desired IP for your Pi, two colons, the gateway address, one colon, the netmask, two colons, “eth0”, colon, “none”.  Make sure that the text is all on one line with a newline at the end, and save the file over the original.  Safely remove the card, put it in your Pi and start it up.  Keep following the tutorial for now.  We’ll sort your Pi out permanently once you’ve logged on and used the text editor a bit.

4.  Logging in

Like any sane computer, the Pi uses SSH to provide an external terminal (or “shell”) in which to do your work.  It is secure because it is encrypted from log in onwards – no one can sniff your password, username or anything you type during your session.  If you use Linux on your home PC then you’ve already got a SSH client, but if you are unlucky enough to be using Windows, you’ll need to download PuTTY from here.  Start PuTTY up and enter the IP address you picked where it says “Host name (or IP address)” and click “Open”.  Linux users, start a shell and type ssh -l pi 192.168.1.5 (replace the 192… with your Pi’s IP address).  The username is “pi” and the password for it is “raspberry”.  You should see this:

Linux raspberrypi 3.1.9+ #168 PREEMPT Sat Jul 14 18:56:31 BST 2012 armv6l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

Type 'startx' to launch a graphical session

NOTICE: the software on this Raspberry Pi has not been fully configured. Please run 'sudo raspi-config'

pi@raspberrypi:~$

Hooray!  You are logged in and the world is your lobster.  From now on we’ll be typing commands to do things.  Whenever you see the line that says “pi@raspberrypi:~$” (or a variant of it), it means the Pi is waiting for you to type something in.

5.  Initial configuring

You see that bit where it says “NOTICE: the software on this Raspberry Pi has not been fully configured. Please run ‘sudo raspi-config'”?  That’s sound advice.  Type sudo raspi-config or copy and paste the words from the login text.

ââââââââââ⤠Raspberry Pi Software Configuration Tool (raspi-config) ââââââââââââ Setup Options                                                                â
â                                                                              â
â    1 Expand Filesystem              Ensures that all of the SD card s        â
â    2 Change User Password           Change password for the default u        â
â    3 Enable Boot to Desktop         Choose whether to boot into a des        â
â    4 Internationalisation Options   Set up language and regional sett        â
â    5 Enable Camera                  Enable this Pi to work with the R        â
â    6 Add to Rastrack                Add this Pi to the online Raspber        â
â    7 Overclock                      Configure overclocking for your P        â
â    8 Advanced Options               Configure advanced settings              â
â    9 About raspi-config             Information about this configurat        â
â                                                                              â
â                                                                              â
â                     <Select>                     <Finish>                    â
â                                                                              â
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ

You will see a menu pop up with loads of options.  Move the highlighted line with the up/down arrow keys and hit return to select an option.  The options in “<>”s are selectable with the tab button, so tabbing twice would take you to the “Finish” option, where you hit return to do it.

  • If your SD card is larger than 2GB then choose option 1 – “Expand Filesystem”.  This will allow you to use all the card’s memory rather than just 2GB of it.
  • Don’t bother with 2 – “Change user password”.  We’ll be getting rid of the user in a minute anyway.
  • Don’t do 3 – “Boot to desktop” either.  We are being macho and using the command line only.
  • Select 4 – “Internationalisation Options” to go to the options page to set the timezone and “locale” (which sets various preferences like number format, date-time format) to your country.  “Timezone” is fairly straightforward, but “locale” is less so.  It offers you a list of baffling lines of text, which is comprised of  language_territory.codeset with abbreviations for “language” and “territory”.  If you are in the UK then “en_GB.UTF-8 UTF-8” is the one you want.  When you find the one you want, hit the space bar to star it and then tab a couple of times to the “OK” button.
  • 7 – Overclock: This setting allows you to speed up your pi by tweaking the clock speed and voltage of the CPU.  Higher values mean your Pi runs faster, but too high a value could make it unstable.  Experiment a bit with it and if you find you have problems, lower the settings until it’s happy.

There are a couple of things in 8 – “Advanced options” that we need to do, so select it and choose:

  • A3 – “Memory Split”: RAM on the Pi is split between the CPU and graphics chip (GPU).  As it’s not plugged into the TV you don’t need graphics.  Choose this option and enter a number for how much memory the GPU should have.  The number to use is 16, which is the minimum memory you can assign for the GPU.
  • A4 – “SSH”: Make sure that this is set to “Enable”.  Otherwise you won’t be able to log in again.

Once you’ve finished with the config program, press Tab twice to highlight “Finish” and hit return.  You can reboot your Pi when prompted or drop back to the command line (“pi@raspberrypi ~ $”) and type sudo reboot to do it manually.  Leave it for a couple of minutes and then log in again (pi/raspberry).  As a quick check to see if your Pi is now using the whole SD card, type df -h

naich@raspberrypi ~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs          3.6G  3.4G   72M  98% /
/dev/root       3.6G  3.4G   72M  98% /
tmpfs            22M  208K   22M   1% /run
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs            44M     0   44M   0% /tmp
tmpfs            10M     0   10M   0% /dev
tmpfs            44M     0   44M   0% /run/shm
/dev/mmcblk0p1   56M   34M   23M  61% /boot
naich@raspberrypi ~ $

Look at the line that starts “rootfs”.  The “Size” column should report something close to the size of your card – in this case it’s a 4GB card.  If it still says it’s under 2GB then the resizing didn’t work.  You could try resizing it with the configuration program again (sudo raspi-config) or use this tutorial.

If you are familiar with Linux on the command line you can stop reading my wibblings now.  You have, for all intents and purposes, installed Debian Wheezy on your Pi.  Go forth and do with it what you will.  The rest of you can read on while we do some basic maintenance and then add some USB storage, install a Bittorrent client to download your perfectly legal torrents and a uPNP Media Server to watch them on your TV, PS3 or whatever.

Continued here…

Yummy Pi – what to do with a Raspberry Pi

June 21st, 2012

So you’ve got your Raspberry Pi and it’s sitting there, staring at you PCB-ily while you are wondering why you ordered it in the first place.  If you don’t know what to do with your Raspberry Pi, don’t bother plugging it into your TV, booting it up and clicking despondently at a few things before chucking it in the loft.  Use it for something useful and learn a bit about Linux at the same time.  Don’t tie up the TV with your Pi, use it on your home network as your faithful assistant – always on and connected to the internet, ready to do whatever you want at any time.  Use it headless (no monitor, keyboard or mouse) and install a whole load of useful stuff on it: a Bittorrent client, media streamer, network-attached-storage or any of these ideas.  You have a PC that is more powerful than the best computer you could buy 10 years ago and it uses less power than a low power light bulb.  It would be a crime not to use it for something.

A Raspberry Pi in a snazzy Lego case

These series of posts are aimed at someone who knows a bit about computers (above the level of randomly clicking at things in a blind panic, but below reprogramming the BIOS with a 9 volt battery and a hair clip) but not much (or indeed anything at all) about Linux.  You will learn to use your Pi at a fairly intimate level, gently stroking its settings by typing in commands and editing files.  This is not pointing and clicking, as you do with Windows, Macs or Linux distributions like Ubuntu, but typing stuff in is not difficult and it makes you feel like a hardcore hacker.  Embrace your inner geek and learn to love your Pi.

1.  Plugging it in

If you want to, you can plug your Raspberry Pi into your TV, stuff a mouse and keyboard up its USB ports and use its (quite slow by all accounts) GUI, but I don’t do these sorts of shenanigans.  I have a simpler setup where it’s just plugged into the network and accessed remotely, with no keyboard, mouse or anything.  To run it this way, you need three things: a power supply, an SD memory card and a bog standard CAT5 network cable.  Don’t panic if you are running your home network wirelessly – your router will have sockets on it for plugging in network cables.  You won’t need physical access to your Pi after the initial set up, so you can leave it next to your router – in the cupboard, under the sofa, or wherever your router lives.

To power it up, you need a 5V power supply that can provide at least 700mA with a mini-USB connector on the lead.  Have a look in that collection of phone chargers you’ve got rattling around in your crap drawer.  Jen’s Samsung charger worked a treat.  Failing that you can buy one for less than a fiver from Amazon – something like a Nokia AC-10x charger..

2.  Booting it up

You need a SD card of at least 2GB, but 4GB is better if you want to install anything.  There isn’t really an upper limit, so 16, 32 or 64GB cards should work, with faster (class 10) cards giving you a faster system overall.  It used to be the case that some cards worked better than others but later firmware versions fixed the problems that some Pis had with faster cards.  If you find that your Pi is not booting, it is worth trying a different type of card just in case.

There is no software built into the Pi, so it boots and runs off the SD card as if it were a hard drive.  That means you need to install all the software it needs on the card before you plug it into the Pi.  This page shows you how to do it. using a disk image that you copy onto the card using a card reader and software on your PC.  Here is where you download the image fileto copy to the card.  Download Raspbian “wheezy”, which is basically Debian optimised for the Pi.

If you have just finished installing the image, unplug the card from the reader now.  Plug the card back into your card reader and a window with a 59MB partition in it should pop up on your PC.  This contains the files that boot the Pi. If you are using Linux, you will also see a 1.9GB partition in another window – this contains the the rest of the files for the Raspbian system.  Because Windows can’t recognise the type of filesystem (EXT3),  Windows users can’t see this partition, but don’t worry about that.  You might be wondering what has happened to the rest of your SD card – you can only see about 2GB of it.  The file system can be adjusted to use the rest of the card’s memory once the Pi is up and running.

Now safely remove the card, lob it in your Pi, plug it into your router with the CAT5 cable and plug in the power supply.  If it’s all OK, the red LED should come on for a few seconds followed by the other ones, with the green one flashing occasionally.  The LEDs are stupidly bright.  Congratulations!  Your Raspberry Pi is now ready for use.  If only the red light is on then something is wrong.  If you have followed all the instructions and have the correct partitions and files on it, then it is probably the card itself which is the problem.  Try a different card and see if that fixes it.

Continued here…

And another thing…

May 29th, 2012

Sorry, you’ve got me started on the Vectra now. The Vectra’s central locking has 2 “features” I’ve not seen on other cars – one press of the remote unlocks the driver’s door and you need another press to unlock the rest of the doors and the boot and filler cap. The reason for this is … absolutely no idea. It’s like it was put in just to piss me off. 95% of the time I have to press it twice and there’s no actual benefit that I can think of in only unlocking one door. Maybe they think that I occasionally want to lock out the wife and kids and go scooting off on my own? Actually… nah, let’s not continue that line of thought.

The other feature is that if you don’t open the drivers door within 30 seconds of unlocking, it locks all the doors again. I can’t count the number of times when this has been useful because I’ve accidentally unlocked the driver’s door. I can’t count them because it’s 0. This has never happened with any car I’ve ever owned. I unlock the door because I want to get in, not on a passing whim or because I like pressing buttons. Any usefulness of this feature in the remote possibility that I might lose my mind and accidentally unlock the doors for no reason, is somewhat outweighed by the number of very real occurrences when I’ve unlocked the doors, been momentarily distracted by children and found myself and my family locked out again.

Now, put these two features together and you get me, attempting to fill up the car and finding the petrol flap is jammed shut. After a few minutes of trying to pry it open I remember that I went out on my own, so I single clicked to unlock the car and only the driver’s door is unlocked. The flap was secure, and thank god it was – a petrol thief might have been passing while I was getting in, looking to empty my tank in the few seconds before I drove off down the road. So I lock the car up again and double unlock to get the flap open, I fill up (75 QUID!!!) and – buggery arseholes, the poxy thing has jammed open now. It’s banging against the lock and won’t close. A few more minutes of thumping and swearing and I remember that since I only locked and unlocked the doors to open the sodding petrol flap, the car has noticed that I didn’t open the driver’s door and has vigilantly locked itself up again, with the petrol flap open. Sure enough I have to unlock it (double sodding click) again in order to close it.

Thank you Vauxhall, for making my life so much easier with your little helpful details. Sorry, I’m going on again aren’t I?

I’m so popular!

March 22nd, 2012

"We must invite Naich. He's so fucking sophisiticated."

Gosh, where do I start.  There are so many people want me to join their exclusive circles.  I had a letter from the Vice Chancellor of Cambridge University (or “Vicey”, as I call him), asking me – actually more like begging me to join him for a swanky reception with canapes and vino.  He used the excuse that it was for my 25 years service working at the uni, but come off it – who wouldn’t want the company of a badly dressed, slightly brain damaged electronics technician, staggering around guzzling wine and belching pastry fumes?

But even more exciting was my email invitation to join the Freemason Illuminati.  I didn’t even realise there was one until I got their mail!  They obviously like the cut of my gib and I was just thinking it was about time I heard from the shadowy evil secret rulers of the world.  If anyone would like any favours once I’ve joined the select elite, let me know.  This is what they sent.  It all seems totally legit.

Date: Sat, 17 Mar 2012 09:30:03 +1200
From: freemason illuminati <noreply@freemason.org>
Reply-To: order@illuminati.umail.net
To: yourorder@fi.org
Subject: we call

You are receiving this mail in regards of the freemason confraternity  of the
whole wide world (FCWWW).

You are moving well in what you are doing but in order to make it easier for
you, we have concluded for you to be a part of us as a member to sign your
life to us and have any thing you need.

Be it any thing in the whole wide world.

You can’t refuse us now for it’s too late.

Get back to us now for your Illuminati membership Order and also for you to
know more about the ancient ILLUMINATI FORUM and also the Orientation and
goals that we pursue.

Get back to acquire your goal now.

I can’t wait to set up some sort of super-villain style base on a Caribbean island.  I’ll need some sidekicks if anyone is interested.  You’ll have to improvise with the sinister weapons until I get set up properly.  I’ll see if I can get some sort of poisoned dart cigarette holder made up, or maybe a miniature gun in a mobile phone, but in the meantime you could use a brick in a sock to bludgeon people to death.

Cat 0 : Linux 1

March 12th, 2012

I went to do some stuff on my PC the other day to find that the cat had been sleeping with her paw on the “Print Screen” button. This button starts up a program that takes a screenshot and brings up a window asking where you want to save it.

Holding down a key keeps repeating the keypress, so as long as the key is held down it’ll keep starting up new copies of the program, again and again and again, as fast as it can.   It is the PC equivalent of sitting stationary in your car with your foot firmly pressed down on the accelerator. The cat had been sitting like that for quite a long time.  Everything had ground to a halt and the status bar was just 1 pixel wide grey stripes. There was a black box on the screen where the last “take a screenshot” window had popped up but the poor PC didn’t have enough CPU left to actually fill it with anything.

The mouse was barely moving so there was no hope of actually using it to close the windows. It was time to use Geek powers and drop to the command line. I hit CTRL-ALT-F2 and waited for a while. Several seconds later the terminal came up and although it took a few seconds for each keypress to register, after a couple of minutes I was actually able to log in. An incantation of “ps -ef |wc -l” showed there were 3,600 processes running. Each screenshot capture takes 3 processes, so there were 1,200 screenshot programs running simultaneously. I gave it some Linux magic – “killall gnome-screenshot” and everything instantly sped up. I did some more killing and everything went back to normal – in fact there were no ill effects whatsoever and the computer worked fine for the rest of the day, with no need for a reboot or anything.

Jimbo once started up 140 text editors which barely slowed the PC down and Luna couldn’t kill it with 1,200 screenshot programs. Linux – impervious to cats and kids.

Update: It’s been pointed out that I should have used “pkill” rather than “killall”.  Killalling, while relatively harmless on a Linux box – a bit like trimming a dog’s claws, is the Unix equivalent of taking it out back and shooting it in the head with a rocket propelled grenade.

A new plan

January 9th, 2012

I want to discover a fundamental force of nature. What I’ll do is give it the unit of a “manilli”. Everyone will wonder why until they realise what 1/1000th of a manilli is. Then they will get that awful tune stuck in their head and hate me.

It’s a bit quiet isn’t it?

December 7th, 2011

I’ve not had much to say for myself recently.  Obviously I’ve had no interesting thoughts since June, and then it was about getting bits of metal out of a skip.  What a life I must lead.

Highlights since the last blog entry:

  • Fixed the brakes on my bike
  • Fixed the washing line
  • Poisoned two rats
  • Pumped up the car’s tyres
  • Went bungee jumping in Wales, fell 200 feet before the rope snapped, crashed head-first into an underground cavern where I discovered that Keith Harris was plotting to use a nuclear arsenal to overthrow the world’s governments and install Orville the Duck as Supreme Overlord of the Earth, beat him up with my bare hands, pulled Orville’s stuffing out and disarmed 24 nuclear bombs using nothing but my knowledge of Portable Appliance Testing and an elastic band the postman had dropped outside the front door
  • Mowed the lawn
  • Bought a long handled spoon

I made one of those up, by the way.