Month: July 2012

IT

Varnish cache: how to detect IPv6

The following VCL code detects if the client is connected using IPv6:

acl isipv6{                     

        "::"/0;

}                       

sub vcl_recv {          

    # [... whatever rules you like ...]

    if(server.ip ~ isipv6){

        # [... whatever rules you like ...]

    }

    # [... whatever rules you like ...]

}

You may want to use that for example for a "you're ipv6 enabled" banner.

© GeekLabInfo Varnish cache: how to detect IPv6 is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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IT

GTK and KDE: unreadable fonts

I just found a note from several years back. Since it may someday be handy to someone, I'm posting it here:

KDE somewhat integrates GTK applications. These applications will get the color schemes from KDE. Sometimes fonts in menu's get rendered unreadable by this.

Wrong styles are defined in /opt/gnome/share/themes/Qt/gtk-2.0/gtkrc:

style "default"

{

  engine "qtengine"

  {

  }

}

class "GtkWidget" style "default"

Disabling this whole block fixed my problem.

© GeekLabInfo GTK and KDE: unreadable fonts is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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IT

Hide the mouse cursor with X

I recently got myself a touch screen, that I mounted near the entrance to welcome visitors. The device was really hard to install, as the drivers for 4 different Linux distros were broken, and only binary drivers are released. The fifth distro finally worked.

One thing that does annoy me however, is that X always shows the cursor. To hide the cursor on a touch screen, you can use the program unclutter:

yum install unclutter
unclutter -idle 0

Unclutter with such a short delay (0 seconds) also makes it impossible to select texts, but for this application, that's just perfect.

© GeekLabInfo Hide the mouse cursor with X is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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IT

Backup your phone with zero keypresses

I created some scripts to backup my Samsung Galaxy S2 to my Fedora 16 system without pressing any keys or even touching the mouse. It works like this:

To backup a SGS2, you go to settings > applications > usb tools on the phone, and click the button. You then connect it to a usb cable. At that moment, two removable devices become visible to the Linux system: one for the SD card, one for the built-in memory. But they still contain no media. Only when you press another button on the phone, the "media are inserted in the devices", triggering a "change" action with the udev daemon.

Configuration of the udev daemon

Create a file /etc/udev/rules.d/71-android-backup.rules:

SUBSYSTEM=="block", ACTION=="change", ENV{ID_SERIAL}=="Android_UMS_Composite_XXXXXXXXXXXXXXXX-0:0", ENV{DISK_MEDIA_CHANGE}=="1", ENV{ID_FS_TYPE}=="vfat", RUN+="/usr/local/bin/androidbackup"

Whenever a (virtual) medium is inserted, a udev change action is triggered. Actually, it gets triggered multiple times, but we only need the one that has the environment variable DISK_MEDIA_CHANGE=1 set.

Action to perform

The action triggered is /usr/local/bin/androidbackup and all parameters are in the environment. So let's create that file. I use a rsnapshot-like operation to backup my data, but without actually using rsnapshot.

#!/bin/bash
 
function msg {
        /usr/bin/logger -t android "$1"
        DISPLAY=:0 qdbus $dbusRef setLabelText "$1"
        DISPLAY=:0 qdbus $dbusRef Set "" value $2
}
 
if [ "$1" != "FORKED" ]; then
        $0 FORKED &
        exit 0
fi
 
if [ -f /etc/sysconfig/androidbackup ]; then
        . /etc/sysconfig/androidbackup
else
        echo /etc/sysconfig/androidbackup does not exist
        exit 0
fi
 
#debug disabled:
#set > /tmp/android/`date +%s`.$RANDOM
 
dbusRef=`kdialog --display :0 --progressbar "Backup android..." 100`
 
msg "Attach $DEVNAME $ACTION $ID_SERIAL" 0
 
if [ ! -e $DESTINATION ]; then
        # I could mkdir -p, but sometimes $DESTINATION could just be a network location that's offline
        msg "Android will not be backed up: $DESTINATION is not okay" 0
        exit 0
fi
 
mkdir -p /mnt/android
 
mount $DEVNAME /mnt/android 
rc=$?
if [ $rc -ne 0 ]; then
        msg "Problem mounting $DEVNAME to /mnt/android: $rc " 0
        mount | grep android 2>&1 | logger -t androidbackup
        exit 0
fi
 
if [ "`mount |grep -i /mnt/android`" == "" ]; then
        msg "Cannot find /mnt/android in mount table" 0
        exit 0
fi
 
msg "Remove old backup" 8
[ -e $DESTINATION/backup.30 ] && rm -rf $DESTINATION/backup.30
 
msg "Start backup" 10
for i in `/usr/bin/seq 30 -1 2`; do 
        if [ -e $DESTINATION/backup.$((i-1)) ]; then
                msg "mv $DESTINATION/backup.$((i-1)) $DESTINATION/backup.$i" 11
                mv $DESTINATION/backup.$((i-1)) $DESTINATION/backup.$i
        fi
done
 
msg "Copy" 40
[ -e $DESTINATION/backup.0 ] && /bin/cp -al $DESTINATION/backup.0 $DESTINATION/backup.1
mkdir -p $DESTINATION/backup.0/
 
msg "Start rsync" 40
/usr/bin/rsync -az --numeric-ids --delete --hard-links /mnt/android/ $DESTINATION/backup.0/
touch $DESTINATION/backup.0/
 
chown -R $CHOWN $DESTINATION/backup.0
 
umount /mnt/android
 
msg "Done" 100
exit 0

Since that file refers to /etc/sysconfig/androidbackup, let's also make that file:

#next line defines the location of all backups
DESTINATION=/home/geeklab/.androidbackup
 
#next line defines the owner of all files copied
CHOWN=geeklab
© GeekLabInfo Backup your phone with zero keypresses is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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