Naich's crappy blog

Continuing from here

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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…

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…

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.

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