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Linux: enable encrypted swap (Ubuntu / Debian)

1. create and enable a "regular" swap partition (fdisk / mkswap / swapon)

2. install ecryptfs-utils and run ecryptfs-setup-swap
sudo apt-get install ecryptfs-utils
sudo ecryptfs-setup-swap

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hping - [send_icmp] Unsupported icmp type

When performing tests you may sometimes want to send specially crafted icmp packets. hping is a handy tool for that.

However, the default behavior is to refuse to send "unsupported" Type/Code combinations. eg
hping3 -c 1 --icmp -C 33 -K 0 192.168.70.1
HPING 192.168.70.1 (wlan0 192.168.70.10): icmp mode set, 28 headers + 0 data bytes
[send_icmp] Unsupported icmp type!

Fortunately, there is an (undocumented) --force-icmp option that you can add to bypass the check:
hping3 -c 1 --icmp --force-icmp -C 33 -K 0 192.168.70.1
HPING 192.168.70.1 (wlan0 192.168.70.10): icmp mode set, 28 headers + 0 data bytes

--- 192.168.70.1 hping statistic ---
1 packets transmitted, 0 packets received, 100% packet loss
round-trip min/avg/max = 0.0/0.0/0.0 ms

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Scanner permissions in Ubuntu Karmic (udev libusb saned problem with udev-acl)

In Ubuntu Karmic (and possibly Jaunty ?), when you install libsane, it adds a file /lib/udev/rules.d/40-libsane.rules which contains rules that match on supported scanners and set the environment variable "libsane_matched" to "yes".

This in turn triggers the following in /lib/udev/rules.d/70-acl.rules:
# USB scanners
ENV{libsane_matched}=="yes", ENV{ACL_MANAGE}="1"
<snip>
# apply ACL for all locally logged in users
LABEL="acl_apply", ENV{ACL_MANAGE}=="?*", TEST=="/var/run/ConsoleKit/database", \
RUN+="udev-acl --action=$env{ACTION} --device=$env{DEVNAME}"

In the end, the result is that an ACL is created for the device, which allows locally logged in users to use it (read/write permission). eg for my scanner:
~# lsusb
Bus 001 Device 005: ID 04b8:011c Seiko Epson Corp. Perfection 3200
~# ls -l /dev/bus/usb/001/005
crw-rw-r--+ 1 root root 189, 4 2009-12-28 00:11 /dev/bus/usb/001/005
~# getfacl /dev/bus/usb/001/005
getfacl: Removing leading '/' from absolute path names
# file: dev/bus/usb/001/005
# owner: root
# group: root
user::rw-
user:crox:rw-
group::rw-
mask::rw-
other::r--
~#

However, I also wanted to allow access to the scanner from other workstations through saned. In older Ubuntu versions, you could just add saned (or whatever user the service runs as) to the scanner group. This no longer works since the device belongs to root:root, and ACLs are added for specific users. The solution that works for me is to create a file /etc/udev/rules.d/99-sane-group.rules with the following contents:
# change group to scanner for sane devices
ENV{libsane_matched}=="yes", GROUP="scanner"

Then you just need to run
sudo udevadm trigger
and the group of the device magically changes to scanner.

Of course you could also add a similar rule specifically for a certain device instead, in my case this would work too:
ATTRS{idVendor}=="1d6b", ATTRS{idProduct}=="0002", GROUP="scanner"


To check that it worked, run the following:
sudo su -s /bin/bash -c 'scanimage -L' saned



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Making a Dell computer running Linux silent (Dell Precision noise problem)

Faced with a noisy Dell Precision 490 computer running Ubuntu Karmic, I found an easy way to reduce the noise level to an acceptable threshold. (fancontrol did not help since it seems not to be compatible with the chipset used by Dell at least on this computer.)

Step 1, install i8kutils:
sudo apt-get install i8kutils

Step 2, add i8k to /etc/modules:
sudo sh -c 'echo i8k >> /etc/modules'

Step 3, edit /etc/default/i8kmon so that it looks like this:
# /etc/default/i8kmon

# Change to one enable i8kmon
ENABLED=1
I8KMON_ARGS="--daemon --nouserconfig --auto"

Step 4, reboot and enjoy!

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Patch for mISDN-1_1_9_2 to support the Eicon DIVA USB ISDN adapter (071d:1005 mISDN)

This is a copy of a post I made to the isdn4linux mailing-list.

The attached patch adds support to mISDN-1_1_9_2 for the Eicon DIVA USB ISDN adapter (071d:1005).

The bits I've added to hfcs_usb.c are from kernel 2.6.31. So far the adapter works fine for me (tested with 1 and 2 concurrent calls to asterisk 1.4.26.1 with chan_misdn).

You can get the patch here: misdn-1.1.9.2-Eicon-Diva-USB.patch.

Comments are set to "moderated" for this entry, please consider whether you should rather post to the list.
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