Your Linux problems, solved! Part 1

Mobile Linux brain Neil Bothwicktackles the most common issues and presents a collection of solutions that’s sure to keep your system running smooth and trouble free. Well, mostly.

“Considering how complex a modern Linux system is, it’s astonishing that it starts up.”
Everyone has a problem with Linux at some point. The important thing is how quickly that problem gets solved.
An amazing element of the open source and computing community is the vast network of help available online in the form of blogs, websites and forums.
Without doubt this is of huge importance in getting issues known and fixed, and it’s wonderful to see how willing the community is to help out complete strangers and beginners alike. That being said, there’s nothing that beats a bit of prior knowledge.
To help arm you with the knowledge you need to keep your Linux systems cheerfully ticking over, we’ve taken our years of experience answering all manner of reader and www.linuxformat.comforum questions and distilled this into a rich brew of condensed Linux knowledge, which will target the top issues that Linux users regularly run into.
In many ways computers are this wobbling tower of intertwined standards, protocols, interfaces and files. Considering just how complex a modern Linux system is, it’s astonishing that a Linux PC manages to successfully complete the delicate dance of powering up, launching the bootloader, handing over to the kernel, loading files of its file system, hopping through init and establishing an X graphical interface with interactive graphical desktop manager, wireless internet connection and all the other services that modern systems provide.
At any stage this wobbling tower can crash down – and when it does, we’re here to help you pick up the pieces! Our guide starts at the beginning with troubleshooting the boot process, moving through basic hardware and system issues, then on to more generic hardware, networking and finally classic desktop problems.
Hopefully you’ll come out of the darkness with at least a few invaluable nuggets of Linux knowledge to help make your Linux experience that little bit smoother and even more enjoyable. So lets turn the page and get fixing!

Getting started

Got boot problems? We tackle the common issues.

Stalled boot

Q: My computer won’t boot. The splash screen comes up and then it just sits there.
A: The first thing to do is be patient – the boot process  may be trying to initialise a piece of hardware, or access  the network before it’s available. These can time out after a  few minutes, either allowing boot to proceed or at least giving  you an error message to work with. In the good old days,  distros used to stream reams of text up the screen as they  were booting, until it became fashionable to hide this with a  splash screen. Unfortunately, the splash screen also hides  any error messages. You can disable the splash screen at the  boot menu: if your computer starts booting without showing  a menu, hold down Esc when it boots to call up the menu.
 If there’s a recovery or safe option, pick that, as it disables the  splash screen and often sets safer (if potentially less efficient)  boot options. Otherwise, put the highlight on your normal  boot option and press E for edit. Find the line that starts with  linuxand look for options like quiet, splash or theme. Delete  these options and press F10 to continue booting.
This won’t fix your problem (unless the problem is the  splash screen itself), but it will let you see what is going on  and either get an error message or an idea of which stage of  the boot is failing at. Then you can investigate further. If it  appears to be a hardware detection issue, try disconnecting  all unnecessary hardware, such as printers, scanners or USB  rocket launchers. Once you can get past the problem, you can  start to fix it.

Boot errors

Q: When I boot I see error messages along the lines of

<script class=”brush: html” type=”syntaxhighlighter”><![CDATA[
Pci Express Device Error. Severity NN. Uncorrected non
Fatal. Pci Bus Error<br/>
Type:N Transaction Layer. Flow Control Protocol N:First.
Receiver 1
This is a problem I’m experiencing on a newly bought
motherboard that works fine with Windows.

A: Hardware working with Windows is no indication that  it’s fault free. The “It works with Windows, ship it and  we’ll fix any other problems with an update” attitude is not  uncommon. With anything motherboard related, the first  step is to check whether there’s a BIOS update available.
 Even with a brand new motherboard, by the time it has  travelled through the shipping and distribution process to get  from the Far East to your computer’s manufacturer and then  to the shop and finally to you, there is usually a new BIOS  available. Flashing a new BIOS can fix a lot of boot problems  but if yours persist, there is more you can do.
You can change the way the kernel addresses the  hardware with a number of parameters you can pass to it at  boot time. At the Grubboot menu (press Esc if it does not  show up by default), highlight your normal boot option and  press E (for edit). Edit the line starting with kernelby adding  some or all of these options to the end of the line, separated  by a space:
noapictimer, acpi=off 
Note the difference in spelling between the second and  third set of options – about all that acpiand apichave in  common is the letters in their names. Press F10 to boot with  the options you added. Once you find a combination that has  the kernel and your hardware co-operating with one another,  make the change permanent by adding the options to GRUB_ CMDLINE_LINUX_DEFAULT and GRUB_CMDLINE_LINUX in  /etc/default/grub, saving the file and updating Grubwith  one of these commands. Which one depends on your distro –  if the first one fails, try the second and then the third.
sudo update-grub2
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
sudo grub2-mkconfig -o /boot/grub/grub.cfg

Re-installing Windows broke Linux

Q: I installed Linux onto my Windows computer and it  gave me the choice of which to use when I turned it  on. I recently had to reinstall Windows and now Linux  has disappeared. I don’t want to reinstall Linux as I  would lose all my documents and settings. Is there any  way to get my Linux back?

A: Linux uses the Grubbootloader to choose between  different boot options, but Windows uses its own  bootloader. A bootloader is a small piece of code embedded  at the start of your hard drive that kickstarts the process of  loading your operating system. When you installed Windows,  it installed its own bootloader, overwriting your existing Grub.
 Don’t worry, it’s only the bootloader code that’s gone – your  Linux system and files are still there, and all you need to do is restore Grub. Some distro install discs have an option to  repair the bootloader, or there’s a more generic option in  Rescatux(on this month’s LXFDVD). Boot from the Rescatux CD and select the Restore Grub option. This will search for  your Linux partitions and ask you to choose the partition that  contains the root filesystem of your Linux installation and  then ask which hard disk you want to install Grubon – usually  /dev/sda, the first disk. The window may go blank for a  worrying amount of time but do not panic or reboot: wait until  it tells you Grubwas re-installed before rebooting, and you  should then get your old boot menu back, with access to your  untouched Linux system.

Dual-booting more than one distro

Q: I know I can dual-boot between Linux and Windows,  but can I do the same with more than one Linux  distro? If so, how do I share my data between them?  How should I partition my disk?
A: Yes, it is possible. Each distro needs its own root partition but you can share the same swapbetween  them all. Having a separate partition for /homeis  recommended – you don’t want to tie your data to a single  distro you may later decide to stop using. While a separate  /homepartition is desirable, don’t use the same home  directory for each distro as there may be incompatibilities  between different versions of the software used. I prefer to  put the distro name in the username, as in “fred-ubuntu”,  “fred-debian”, etc. As long as each user has the same UID –  most installers make the first user 1000 – you’ll have write  access to all of them, then you can create symlinks for  important data directories, like documents, music, photos  and so on, to share these files between all distros while  keeping the configuration files separate.
As far as the boot menu is concerned, pick one distro as  your main one and let that handle booting. Every time you  install a new distro, skip the option to install a bootloader if  possible. Then reboot into the main one and run: sudo grub-mkconfig -o /boot/grub/grub.cfg to update the boot menu.

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Removing a distro broke everything

Q: I deleted Linux partitions from my computer, in  preparation for installing something else. Now I  cannot boot it. All I get is a messagethat Grubcannot  find files and a prompt saying grub rescue>. I can’t even  boot into Windows.
A: While the initial boot code for Grubis stored in the  Master Boot Record (MBR) at the start of your hard disk, this is a very small space. So the initial Grubcode loads  files and configuration information from the grubor grub2 directory on your Linux boot partition. When you removed  that partition, you left Grubnowhere to go. If you are planning  on installing another distro in the now-empty space, simply  run the installer and it will set up Grubfor you, detecting your  Windows system too, and all will be well after a reboot.
If you are using the space for an existing Windows or Linux  installation, you need to either set up Grubfor the other Linux  system or reinstall the Windows bootloader. The easiest way  to reset Grubis use the Restore Grub option on the Rescatux live CD – choose the Linux installation you want to be  responsible for holding the Grubfiles. Restoring the Windows  bootloader involves booting the Windows disc (or rescue  partition) and running one of these commands, depending on  the Windows version. For Windows XP it’s the following:
For Vista and Windows 7 and 8 it’s:
bootrec /fixboot
bootrec /fixmbr
bootrec /rebuildbcd
When your computer won’t even boot, a live CD is a  godsend, so it pays to always have one handy. A live CD is a  complete Linux environment that boots from a CD and needs  no installation, or even access to a hard drive. Apart from  being very handy for being used as a portable distro or as a  sampler to try a different distro without installing it, a live CD
“A separate /home partition is  desirable, but don’t use the  same directory for each distro.”
is ideal for a rescue system. There are some dedicated rescue  CDs, such as System Rescue CD, Rescatux (both on the  LXFDVD this month) and Grml, but most distro installer discs  nowadays boot into a live environment that contains enough  software to fix many problems.
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