Ask Klaus!

Ask Klaus!

Article from Issue 96/2008

Klaus Knopper is the creator of Knoppix and co-founder of the 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: klaus@linux-magazine.com

Asus with Hardy

Question:

My Asus M2V-MX-based desktop suspends well in Windows Vista, but it does not suspend in Ubuntu Hardy. I have changed S3 and ACPI versions in the BIOS to see if that works. Although it causes some differences in behavior, the system still does not work in Ubuntu. What should I do?

Answer:

Some information is missing in your description that could help solve the problem.

Do you mean "suspend to RAM" (STR) or "suspend to disk" (S2D)?

Is the problem that suspend just does not do anything, or is the problem that the notebook does not wake up from suspend mode? I'll give you a short overview on what needs to be done to use suspend to RAM and suspend to disk here.

To use suspend to disk, you need to enable this feature in the kernel. (I assume that this is already done in Ubuntu.) See Figure 1.

Figure 1: Screen shot from the kernel config regarding suspend to disk.

For suspend to disk, the kernel also needs to know how and where to store the content of your notebook's RAM while it is in power-off mode.

The "where" part is configured at the kernel boot command line. Mine looks like this:

$ cat /proc/cmdline
 ... resume=/dev/hda3 ...

With this preset boot option, the kernel knows that the partition, which possibly contains a suspended system, is the third partition on the first IDE hard disk in my setup. On boot, the kernel will automatically try to restore a saved session from this partition when this option is present. To modify the boot kernel command line, you have to change the APPEND line in your bootloader's setup (/etc/lilo.conf for LILO, with LILO being called after a change, or /boot/grub/grub.cfg or menu.lst for the grub bootloader). As a last resort, you can type the option in the bootloader's interactive mode.

On the swap partition, which will also become the "hibernate" partition, you need to reserve space about the size of your RAM.

So, please check to see whether your free swap space is large enough to hold the content of your computer's memory (see Listing 1).

Listing 1

Free swap space

01 $ grep MemTotal /proc/meminfo
02 MemTotal:      1295172 kB
03
04 $ cat /proc/swaps
05 Filename  Type      Size    Used    Priority
06 /dev/hda3 partition 1959920 664036  -1

The example in Listing 1 shows that this computer has about 1.2GB RAM, and 1.9GB of swap, so suspend to disk is possible.

In your setup, if the available swap space is lower than RAM plus swap in use, then suspend to disk will just fail and you would have to repartition the hard drive for a larger swap partition to make it work.

As soon as swap and the boot command line are set up, you can start the suspend procedure by telling the kernel to freeze then store the running system to disk.

Before this, sending a couple of sync commands is a good idea, just in case that unwritten data gets lost because of a failed wake up later. (Sending only one might not be sufficient because of its asynchronous nature.) You must be root for this procedure:

# sync; sync; sync
# echo shutdown > /sys/power/disk
# echo disk > /sys/power/state

Now the kernel should switch to text console mode and display what it's doing. In case of failure, you will see an error message in the output of dmesg.

Depending on how well ACPI works on your notebook, using

# echo platform > /sys/power/disk
# echo disk > /sys/power/state

instead of the previous suggestion might work even better because the ACPI BIOS might know how to switch peripheral devices to suspend mode in order to wake up correctly later.

After freezing processes, the kernel will write the entire system state to the swap partition and power off the system.

On next boot, the kernel will search for a hibernate signature on the swap partition and load the suspended system from there if at all possible.

Some things that could go wrong when resuming:

  1. Some hardware does not reinitialize properly when being awoken from suspend, so your system freezes. This result is known to happen with non-suspendable sound drivers.To be on the safe side, make sure that in your own suspend/resume script, all drivers known to be unstable after wake up are unloaded.Example (before suspend):

    fuser -k /dev/dsp # Stop sound output
    rmmod snd_intel8x0 # Unload onboard sound driver
  2. Because of the way the kernel has been configured in a specific distribution, the swap partition might not be accessible early enough to be able to read from it. For example, if hard disk controller drivers are not statically compiled into the kernel, the kernel might not have a chance to initialize the resume procedure later if the initial ramdisk containing the drivers does not explicitly do this.

Again, the boot/kernel log shown by dmesg might give a hint about what went wrong.

To suspend to RAM (if supported), use mem instead of disk in the suspend commands above.

Apparently, you don't need a suspend partition for this; standby could also be an option, which will only reduce power consumption of some devices but not really suspend the system:

# echo mem > /sys/power/state

or

# echo standby > /sys/power/state

Instead of using the newer /sys/power/… interface, you can also try the ACPI sleep states control file:

# echo 4 > /proc/acpi/sleep # Suspend-to-disk

or

# echo 3 > /proc/acpi/sleep # Suspend-to-ram

USB Wireless Broadband

Question:

I have a three USB wireless broadband Huawei HSDPA CE0682 modem. I cannot get it to work on the Fedora 8. Can you explain why it is difficult to add any USB modem to the Fedora, Red Hat, and Ubuntu platforms?

Answer:

I'm afraid that only the original hardware manufacturer knows why they only provide Windows drivers for their hardware. If the "modem" has a DHCP mode in which it distributes addresses to an Ethernet-networked computer automatically, you should be able to use it without any special drivers. For closed, proprietary USB protocols that only the hardware manufacturer knows about, it is a very tiresome – and in no way cost-effective – task to develop a driver via reverse engineering. Therefore, almost nobody will do this for free.

A company's strategic decision to sell hardware that works only for a specific operating system does not have a reasonable technical solution. The best advice I could give is to return the apparently defective device as a warranty case (it does not work, does it?) and claim your money back.

Puppy on Pen Drive

Question:

I am a university student and an amateur Linux user. Can you tell me how to install mbr.bin on my pen drive? I want to boot a version of Pendrivelinux from this device. Is it possible to install from Puppy 3.10? It never works when I try to find it with the instruction:

locate mbr.bin

Also, I would like to know whether it is possible to install SysLinux with the following command:

syslinux -s /dev/sda1

I have already visited pendrivelinux.com and followed the instructions, but I always have problems booting from my pen drive.

Another problem is that the machines I have access to only have 256MB of RAM, so I can't boot into Ubuntu 7.10 or 8.04. If I understand things correctly, with these versions of Ubuntu, it is possible to install LILO and SysLinux.

Answer:

Making a FAT16/FAT32-formatted USB pen bootable only takes a few commands. In this example, the pen drive is present as /dev/sdc (Listing 2).

Listing 2

Pen drive example

01 # fdisk -l /dev/sdc
02 Disk /dev/sdc: 8021 MB, 8021606400 bytes
03 16 heads, 32 sectors/track, 30600 cylinders
04 Units = cylinders of 512 * 512 = 262144 bytes
05 Disk identifier: 0x10d72c95
06
07 Device    Boot Start  End   Blocks   Id  System
08 /dev/sdc1 *    16     30600 7829568   c  W95 FAT32 (LBA)

This partition table is already perfect for "boot from USB hard disk" BIOS mode. The first partition is of FAT(32) type and marked as "bootable."

If just the "bootable" flag for the first partition is missing, it can be added with:

# sfdisk -A1 /dev/sdc

Usually, you do not need a special boot record like the mbr.bin you asked about. But if your computer needs one and you have found a customized boot record file recommended for a specific purpose (it should be a maximum of only 488 bytes), you can install this custom boot record by just copying it over to the device file:

# cat mbr.bin > /dev/sdc

You must wait for a while until new data has been flushed to disk or enforce it by calling sync or the eject commands below.

After this, check to see whether the partitioning of the pen drive is still OK. To let the kernel know that partitioning data has been changed, you might have to reconnect the drive. The easiest way to do so is with

# eject /dev/sdc
# eject -t /dev/sdc

or you can physically remove and re-insert the drive.

Instead of installing a custom master boot record, I recommend that you first try a standard one:

# ms-sys -s /dev/sdc

For installing the SysLinux bootloader on the first partition, the command is:

# syslinux /dev/sdc1

Note that you really have to type the partition name here, not the entire device name.

SysLinux is a kind of "DOS program," just written to a specific, bootable location on the partition; therefore, you cannot just "mount and copy" ldlinux.sys to the drive.

For USB pen drives, the -s[low] option of SysLinux should not be necessary; however, if not even the SysLinux boot command line is displayed, but the pen drive seems to be accessed, it is worth a try.

SysLinux requires a configuration file, syslinux.cfg, which tells SysLinux what kind of operating system to start and, possibly, also to load a ramdisk.

The following is an example of syslinux.cfg contents:

default linux
timeout 10
prompt 1
label linux
  kernel linux
  append initrd=minirt.gz root=/dev/ram0

Linux kernel (linux) and initial ramdisk (minirt.gz) must be copied to the same partition containing the bootloader. The Linux filesystem itself can be located on a separate partition, formatted with a Linux filesystem such as ext2, ext3, or ReiserFS, if it is not installed as a loopback image file.

In the case of installing Knoppix on a pen drive, you would just copy the KNOPPIX directory to the FAT(32) partition of the pen drive, which contains all the data and programs:

# mkdir -p /media/sdc1
# mount -t vfat -o shortname=winnt /dev/sdc1 /media/sdc1
# cp -rL syslinux.cfg linux minirt.gz KNOPPIX ... /media/sdc1/
# umount /media/sdc1

Please note the shortname=winnt mount option, which will create file names on the FAT partition with lower- and uppercase spelling, just as in the original file name. Most Live distributions are picky about upper- and lowercase in file names.

After all files needed to run the distribution have been copied (and you have created a Linux partition containing the distribution's filesystem), you should be able to boot from the pen drive.

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    Nearly all motherboards have a power management feature designed to power down the computer and put it into suspend mode. In real life, this feature does not always work. Linux has a software-based workaround for the dysfunctional suspend.

  • Ask Klaus!

    Klaus Knopper is the creator of Knoppix and co-founder of the 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: klaus@linux-magazine.com

  • ASK KLAUS!

    Klaus Knopper is the creator of Knoppix and co-founder of the 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: klaus@linux-magazine. com

  • Ask Klaus!

    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

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