route icmp to a different gateway 
Thursday, July 28, 2011, 16:17
Posted by Administrator
echo 100 icmp_route >> /etc/iproute2/rt_tables
ip rule add fwmark 1 table icmp_route
ip route add default via IP_OF_NOT_DEFAULT_GATEWAY dev eth0 table icmp_route

iptables -t mangle -A OUTPUT -d IP_TO_PING -p icmp -j MARK --set-mark 1


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USB: uss720 fixup refcount position 
Monday, March 28, 2011, 14:24 - Patches
Posted by Administrator
My testprog do a lot of bitbang - after hours i got following warning and my machine lockups:

WARNING: at /build/buildd/linux-2.6.38/lib/kref.c:34

After debugging uss720 driver i discovered that the completion callback was called before usb_submit_urb returns.
The callback frees the request structure that is krefed on return by usb_submit_urb.
--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -177,12 +177,11 @@ static struct uss720_async_request *submit_async_request(...
        spin_lock_irqsave(&priv->asynclock, flags);
        list_add_tail(&rq->asynclist, &priv->asynclist);
        spin_unlock_irqrestore(&priv->asynclock, flags);
+       kref_get(&rq->ref_count);
        ret = usb_submit_urb(rq->urb, mem_flags);
-       if (!ret) {
-               kref_get(&rq->ref_count);
+       if (!ret)
                return rq;
-       }
-       kref_put(&rq->ref_count, destroy_async);
+       destroy_async(&rq->ref_count);
        err("submit_async_request submit_urb failed with %d", ret);
        return NULL;
 }

http://git.kernel.org/?p=linux/kernel/g ... 5b45be8688

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fast reboot with kexec 
Friday, March 4, 2011, 15:15 - System, Debian/Ubuntu
Posted by Administrator
sudo apt-get install kexec-tools

change LOAD_KEXEC to true in /etc/default/kexec

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record a video with ffmpeg from a webcam with audio 
Monday, January 31, 2011, 18:49 - System
Posted by Administrator
First activate and rise webcam audio input level with alsamixer.

ffmpeg -f video4linux2 -i /dev/video0 -pix_fmt yuv420p -s vga -r 8 -f alsa -ac 1 -ar 16000 -i hw:1,0 -vcodec mpeg4 -b 400k -acodec libmp3lame -ab 80k video.avi

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key remap on keyboard for console and X 
Thursday, January 13, 2011, 16:45 - System, Debian/Ubuntu
Posted by Administrator
I got a funny viennese dialect keyboard, but after start using it i missed a key '<,>,|' :-(

So i searched for a way to remap 'AltGr + y' to '|', 'AltGr + ,' to '<' and 'AltGr + .' to '>'

Console


evaluate the key to change with

#> sudo showkey -s

press the key

here y is 0x2c = 44
here , is 0x33 = 51
here . is 0x34 = 52

test remap with

echo "altgr keycode 44 = bar" | loadkeys

bar is a symbolic name i found at German-Howto

Finally i extended /etc/rc.local with
LOADKEYS=$(which loadkeys)
if [ -x $LOADKEYS ]; then
  cat << EOT | $LOADKEYS
altgr keycode 44 = bar
altgr keycode 51 = less
altgr keycode 52 = greater
EOT
  unset LOADKEYS
fi

Xorg



evaluate the key to change with

#> xev

press the key

here y is keycode 52
here , is keycode 59
here . is keycode 60

test remap with

xmodmap -e "keycode 52 = y Y y Y bar"

dump keys with

#> xmodmap -pke > ~/.Xmodmap

remove all lines except lines starting with desired keycodes to change.

my ~/.Xmodmap now looks like
keycode  52 = y Y y Y bar U203A guillemotright
keycode  59 = comma semicolon comma semicolon less multiply periodcentered
keycode  60 = period colon period colon greater division U2026


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