Klaus Knopper answers your Linux questions

Ask Klaus

Article from Issue 152/2013
Author(s):

Klaus Knopper is the creator of Knoppix and co-founder of LinuxTag expo. He works as a teacher, programmer, and consultant. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to: klaus@linux-magazine.com

bootonly Image

Hi Klaus: I think Knoppix is a very good product and like using it, but I am missing the boot-only version .iso for 7.0.5 – like KNOPPIX_V7.0.5bootonly-2012-12-21-EN. It is not on any of the mirrors I have checked. (I am aware that it should be possible to create a boot-only ISO, like when running in a virtual box).

My BIOS Fujitsu Siemens // Phoenix Technologies Ltd version 4.06 Rev. 1.05.1527, date: 03/12/2003, does not allow booting from a USB. It seems it is not possible to boot the 7.0.5 USB version from the CD KNOPPIX_V7.0.4bootonly-2012-08-20-EN without losing some setup. (It works fine, of course, with 7.0.4 USB.)

Hope you will take the time to answer.

Kind Regards, Hans Kurt Ibsen

You can find the "bootonly" image, which is also valid for the full DVD installation, in the CD directory on the mirrors, for example, here:

ftp://ftp.uni-kl.de/pub/linux/knoppix/

The bootonly image contains just the boot folder containing the isolinux bootloader and the kernel matching the kernel modules on the DVD (i.e., you cannot boot an older bootonly CD for a newer version of Knoppix, and if you do, most drivers will not work because of mismatching modules).

To create the bootonly version yourself, you can do the following:

  1. Create an empty folder (e.g., bootonly-cd). Copy the content of the boot folder of your Knoppix DVD there. If you already have an installed USB flash disk version ready, you need to rename some files and folders in the target directory (bootonly-cd):
  • Rename bootonly-cd/boot/syslinux to bootonly-cd/boot/isolinux.
  • Rename bootonly-cd/boot/isolinux/syslinux.cfg to bootonly-cd/boot/isolinux/isolinux.cfg.
  • Copy the isolinux bootloader from /usr/lib/syslinux/isolinux.bin to the bootonly-cd/boot/isolinux/ folder.
  1. Make sure the directory is writable with: chmod -R u+w bootonly-cd.
  2. Create the ISO:

    mkisofs -input-charset ISO-8859-1 \
       -pad -l -r -J -V "KNOPPIX_BOOT" \
       -A "KNOPPIX_BOOT" \
       -no-emul-boot \
       -boot-load-size 4 \
       -boot-info-table \
       -b boot/isolinux/isolinux.bin \
       -c boot/isolinux/boot.cat \
       -hide-rr-moved \
       -o bootonly-cd.iso bootonly-cd

You can then burn the bootable image bootonly-cd.iso to a fresh CD medium.

Data Partitions

Hi Klaus: Just a quick one. I have two partitions on my hard drive. The first (formatted with ReiserFS) has the Knoppix OS, while the other (formatted with ext4) is supposed to be the data drive. However, I cannot write to the data drive. What do I do?

Blondie

I suppose you mount the data partition to a specific location, for example /opt. This is just an example using the shell, assuming that the disk in question is the first one; /dev/sda1 is the system partition, and /dev/sda2 is the ext4 (data) partition:

sudo mkdir -p /opt
sudo mount -t ext4 /dev/sda2 /opt

or (usually, Linux can determine the filesystem without the -t option):

sudo mount /dev/sda2 /opt

I assume that this part still works for you, so the filesystem is OK.

Now, ext4 (like all Unix-based file systems) supports permissions that apply to read/write/execute operations. You can check for the current permission set of the mounted partition's root directory by doing:

ls -ld /opt/

If the output looks like this:

drwx--- 12 root root 344  9. Nov 00:58 /opt/

then only the system administrator can access the filesystem. This may be the (secure) default when creating the partition's filesystem.

If you want to change permissions to allow read/write/execution or to change the directory for everyone, you should change the partition's root directory permissions like this:

sudo chmod 777 /opt/

or "give away" the partition's root directory to the user who is supposed to use it:

sudo chown username /opt/

The new permissions are permanently stored on the hard disk partition. If there are already subdirectories on the disk that you want to open for read/write as well, you can add option -R (capital R!) to chmod or chown for directory recursion.

Cooling Mayah

Klaus: I run Linux Mint Mayah (13) on an old laptop for my daughter. Periodically, the computer will freeze, and when I feel the bottom it's extremely hot. (It's in a docking station, so I have to remove it from the docking station to feel how hot it is.) I suspect that's causing it to lock up. It will not reboot when it's in that state, but if we wait a while for it to cool, it will restart.

What are the best Linux utilities I can use to get a handle on cooling? Is it possible there's something wrong with the way Linux is controlling the fan(s)? How can I tell?

Regards, Kurt

Your assumption is probably correct: There is a cooling problem. It can have several causes and several solutions.

  1. If the notebook is very old, the fan and heat sinks may simply be clogged with dirt and dust. Turn off the notebook and use a strong vacuum cleaner on the air holes of your notebook, but only in short intervals, to clean out the air channels.

Warning: This can break cooling fans if their gear is severely worn out, so do this at your own risk. In many cases, however, it can save you the effort of taking your notebook apart for cleaning.

If you notice a significantly cooler case and less noise and fan speed after cleaning the fan and switching the computer back on, the procedure was successful.

  1. It may be a software problem. Is the load displayed with uptime (the three floating point numbers at the end) more than 1? It should be close to zero if the computer isn't doing anything. You can check with top for potential processes that consume CPU time for no apparent reason and try stopping those processes to see if it helps reduce CPU usage.

For example, you can temporarily suspend all Java processes that may have been spawned by browser plugins with:

killall -STOP java

and re-activate them using:

killall -CONT java
  1. Your graphics card might not be clocked correctly, set to run at maximum power always, or is running inefficiently. Solution: When using an NVidia+Intel dual graphics chipset, disable the most power-consuming NVidia chip and only use the Intel onboard chipset.
  2. Usually, ACPI should take care of power management, but for some notebooks, it fails to detect the optimal settings. In this case, you can help your kernel decide on better settings by using the acpi_osi kernel boot option, like acpi_iso=Linux or acpi_osi='!Windows 2009' (="Not Windows"). If this changes the fan behavior for the better, you can add the option to your bootloader configuration permanently. Using acpi_osi=… can also fix issues with backlight control and function keys of various notebooks.
  3. Try to tune power consumption of devices using PowerTOP (Figure 1):

    Figure 1: With PowerTOP, you can diagnose problems with power consumption and power management.
    sudo powertop

The PowerTOP [1] package is available in many Debian-based distributions. The power management settings that can be tuned for hardware drivers are present in the Tunables tab.

Infos

  1. PowerTOP: https://01.org/powertop/

The Author

Klaus Knopper is the creator of Knoppix and co-founder of LinuxTag expo. He currently works as a teacher, programmer, and consultant. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to: mailto:klaus@linux-magazine.com.

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