Ask Klaus

Suspended State

Hi Klaus: I switched to Debian last year, coming from Windows XP. What a great experience! Nevertheless, I'm still learning a lot, and sometimes I get surprised.

I have a laptop and a desktop, both quad-cores with 8GB memory, with Debian Wheezy 64-bit running fine. When I prepare a presentation, I like to set up everything, start required applications, open documents, and put my laptop to Hibernate using the user menu. (I don't use Suspend because of my dying battery.) But the behavior is strange: The laptop saves its context, shuts down, restarts, and restores the context. I cannot get it to hibernate. The same thing happens on the desktop! Did I miss a parameter in Wheezy? Thanks for your help. Best regards, Fred

Answer: For "suspend to disk" (which is what is commonly meant by "hibernate"), you need a kernel option in the APPEND command line of your bootloader that tells the system on which partition the data should be saved to and restored from later. It is usually the swap partition, and it should be somewhat larger than the physical RAM present.

Example: Your RAM size is 8GB, the swap partition shown with

cat /proc/swaps

in the shell is /dev/sda2, and it's at least 8GB in size. In this case, the correct boot command line for working hibernation would be:


You can set it in your GRUB configuration – in either the /etc/grub.d/* or /etc/default/grub file – then call grub-mkconfig as root. For GRUB1, you simply change /boot/grub/menu.lst. You can cause a suspend to disk manually with:

echo -n disk | sudo tee /sys/power/state

Unfortunately, not all notebooks can be convinced to suspend to disk and wake up again without more tuning. If the kernel still does not manage to freeze all processes and I/O resources, it will cancel the suspend procedure and immediately go back to the desktop, which is what you already have observed. You could also try the "suspend to memory" option, if you replace your notebook's battery with a good one, which may be an alternative if suspend to disk does not work. Try

echo -n disk | sudo tee /sys/power/state

for a quick test.

Booting via PXE

Dear Klaus, Trying to PXE-boot Knoppix 7.2 is virtually driving me crazy. Basically it works, but it works fine only if the booting client has an Intel E1000 network adapter. On others, the system seems to miss a matching network driver and the boot process breaks. As you might see from my article in a recent Linux Magazine [9], I do not seem to be a total dummy. I have a couple of other systems PXE booting fine already, including the most harmful Window$ PE. I think it worked even with previous Knoppix releases.

Any hints/ideas?

Kind regards, Fritz

Answer: I assume you were using the Knoppix terminal server to create the initial ramdisk needed for booting via PXE (Figure 1). Although kernel and ramdisk are transferred from the TFTP server by the bootloader without needing drivers, after the Linux kernel starts, you need indeed a matching kernel module for the specific network card in your computer (Figure 2), so that the Knoppix filesystem can be mounted via NFS.

Figure 1: Selecting Knoppix Terminal Server.
Figure 2: Selecting a network card.

To include everything necessary, Knoppix will build a set of network drivers and their dependencies based on a list of common PXE-capable network cards and a manual selection.

If, in spite of selecting the correct network card(s), the necessary modules are still not included in the ramdisk, it's a bug, and I would be glad if you email me the network card name and the module in question.


  1. NVidia code names:
  2. Installing Ubuntu on a MacBook:
  3. Installing Ubuntu on a MacBook Pro:
  4. Linux on a Macintosh:
  5. "Ask Klaus!" by Klaus Knopper, Linux Magazine, issue 150, pg. 52:
  6. "Ask Klaus!" by Klaus Knopper, Linux Magazine, issue 157, pg. 56:
  7. CR2032 battery:
  8. Midori:
  9. "DHCP and DNS on Rasp Pi" by Friedrich Hotz, Linux Magazine, Issue 159, February 2014, pg. 30

The Author

Klaus Knopper is the creator of Knoppix and co-founder of LinuxTag expo. He currently is a Professor, Dipl. Ing., at the University of Applied Sciences Kaiserslautern. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to:

Buy this article as PDF

Express-Checkout as PDF
Price $2.95
(incl. VAT)

Buy Linux Magazine

Get it on Google Play

US / Canada

Get it on Google Play

UK / Australia

Related content

  • Ask Klaus

    NVidia graphics problems and setting up an FTP server.

  • Ask Klaus

    Klaus looks at problems with VNC-based shared desktops and a frozen screen with an Nvidia card.

  • Interview: Klaus Knopper

    Ten is a fair age for a Linux distribution that doesn’t have massive staff resources to back it up. Klaus Knopper looks back with a sense of satisfaction after just having compiled version 6.4. As a tribute to the community, this version includes only free software.

  • Ask Klaus!
  • Knoppix 6.3 Exclusive!

    Knoppix creator (and Q&A mastermind) Klaus Knopper shares some insights on the latest release.

comments powered by Disqus