I often need to quickly setup a router using my linux laptop and hence documenting the general steps.

Lets assume wlan0 is the internet facing interface while eth0 is the LAN interface.

Add/Edit the following in /etc/sysctl.conf

net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 1

Execute the following command to setup the sysctl values.

sudo sysctl -p /etc/sysctl.conf

Make sure the default route is pointing to wlan0

Masquerade on the internet facing interface i.e. wlan0

sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE

Now give eth0 an IP and use an IP in the same broadcast range as eth0 for the device sitting on the LAN.

For eg

sudo ifconfig eth0 192.168.137.1

And now use 192.168.137.2 for the device on the LAN network.

Additional step could be to setup a dhcpd server on the eth0 interface. Here’s a sample dhcpd configuration

default-lease-time 600;
max-lease-time 7200;
subnet 192.168.137.0 netmask 255.255.255.0 {
 range 192.168.137.2 192.168.137.254;
}

Now to run the dhcpd server on eth0

sudo dhcpd -f -cf /etc/dhcpd.conf eth0

Remove the -f if you want to run dhcpd in background.

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer

My skype started crashing all of a sudden with the above error. The suggested fix for now is to set enable-shm = no in /etc/pulse/daemon.conf or /etc/pulse/server.conf, whichever file your distribution uses. Restart X after updating the configuration.

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I was surprised that iptables modules are not loaded automatically on ArchLinux. Here’s how you load them. Dump the following lines in any file (for eg. netfilter.conf) under modules-load.d and restart your machine. Alternatively load the modules manually if you want to avoid restarting.

@~ 1028$ cat /etc/modules-load.d/netfilter.conf 
x_tables
ip_tables
iptable_filter
iptable_mangle
nf_conntrack
nf_defrag_ipv4
nf_conntrack_ipv4
nf_nat
iptable_nat

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Sample Kernel Build with the new F2FS filesystem by Samsung

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Just read about this package on AUR (Arch Linux User Repository) which compresses kernel modules using xz compression, so decided to make a note for myself that I should use this technique when required.

https://aur.archlinux.org/packages.php?ID=64213

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer

I have been using a MacBook Pro at work for the past 6 months. I’m not a huge fan of either the MacBook or Mac OS X. OS X according to me is highly bloated and a very poor unix platform. Try entering a command line option at the end of a command – For eg. ls * -l. Applications are installed in their individual directories and are almost never in the path when one needs to execute them from the command line. However one of the features that I grew to love about MacBook is the multi-touch trackpad, especially the two-finger scrolling. Having shifted to Arch Linux for the past month or so, I had been missing the two-finger scrolling. The trackpad that comes with my Lenovo Thinkpad recognizes multi-touch gestures. So I decided to look up how to get two finger scrolling to work and it was surprisingly simple.

You should install the xf86-input-synaptics package if you don’t have it already.

Step 1 is to update the Xorg Synaptics Configuration. In Arch Linux, this resides at /etc/X11/xorg.conf.d/10-synaptics.conf.

Section "InputClass"
Identifier "touchpad catchall"
Driver "synaptics"
MatchIsTouchpad "on"
MatchDevicePath "/dev/input/event*"
  Option "TapButton1" "1"
  Option "TapButton2" "2"
  Option "TapButton3" "3"
  Option "VertEdgeScroll" "on"
  Option "VertTwoFingerScroll" "on"
  Option "HorizEdgeScroll" "on"
  Option "HorizTwoFingerScroll" "on"
  Option "CircularScrolling" "on"
  Option "CircScrollTrigger" "2"
  Option "EmulateTwoFingerMinZ" "40"
  Option "EmulateTwoFingerMinW" "8"
  Option "CoastingSpeed" "0"
EndSection

Step 2: Logout and Login back into your Gnome/Unity Session

Step 3: Open the ‘Mouse and Touchpad’ section under ‘System Settings’ and enable ‘Two-finger scrolling’. Screenshot below.

The above configurations were enough for me to get two finger scrolling to work. Awesome!

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I just added a package on AUR which enables using Picasa as a Photo Viewer. Got the inspiration from here.

If you already have yaourt installed, then installing the application is a breeze.

yaourt -S picasa-photo-viewer

Sample installation log is shown in the following screenshot

Ubuntu Tweak is a good utility to change the default photo viewer to Picasa, looking for a ‘PicasaPhotoViewer’ application in the list.

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Setting up your own package repository is probably the easiest in Arch Linux compared to other Linux Distros. I’m going to jot down what I did for the Unity For Arch Linux Repository that I created. This is a generic set of instructions and will have to adapted for different environments.

• Create all the packages that you want to host in the repository (*.pkg.tar.xz files). Lets assume that all the compiled pacakages are in the directory BUILD-DIR.
• Create a directory structure for your packages.

mkdir ~/repo-dir
mkdir ~/repo-dir/x86_64
mkdir ~/repo-dir/i686

• Copy the *.pkg.tar.xz files in to appropriate directories.

  
  find BUILD-DIR -name *x86_64.pkg.tar.xz -exec cp '{}' ~/repo-dir/x86_64/ \;
  find BUILD-DIR -name *i686.pkg.tar.xz -exec cp '{}' ~/repo-dir/i686/ \;
  find BUILD-DIR -name *any.pkg.tar.xz -exec cp '{}' ~/repo-dir/x86_64/ \;
  find BUILD-DIR -name *any.pkg.tar.xz -exec cp '{}' ~/repo-dir/i686/ \;
  

• Create the package database. Replace repo-name with whatever name you want

  
  pushd ~/repo-dir/x86_64/
  repo-add ./repo-name.db.tar.gz ./*.pkg.tar.xz
  popd
  pushd ~/repo-dir/i686/
  repo-add ./repo-name.db.tar.gz ./*.pkg.tar.xz
  popd
  

• Tar up the packages.

  
  pushd ~/repo-dir/
  tar -cvzf ../packages.tar.gz .
  

• Create a Domain/Sub-domain to host the packages. Lets say the domain is al.humbug.in.
• Copy packages to your server and untar it inside the public folder of your domain/sub-domain

  
  scp packages.tar.gz pratik@al.humbug.in:~
  cd ~/al.humbug.in
  tar -zxvf ../packages.tar.gz
  

• Add the respository to pacman.conf. Change repo-name to whatever you used earlier.

[repo-name]
Server = http://al.humbug.in/$arch

• We are done now, synchronize the package repository and install your packages and distribute it to others.

  
  sudo pacman -Syu
  sudo pacman -S <package name>
  

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer

As I mentioned in my earlier blog posts, I have started using Unity on Arch Linux. However the packages that are hosted at http://unity.xe-xe.org/ haven’t been updated in a while and has resulted in some conflicts with the updates coming through the main repositories. I have written an email to the person who’s managing the repo, but decided to build my own packages as well. This is how I setup a pristine chroot environment to build the Unity PKGBUILDS created by Xiao-Long Chen. I’m not sure if its the prescribed way to do it, but it works!

Steps to setup the chroot environment to build packages using ABS:

sudo pacman -S devtools
mkdir ~/Developer/unity/chroot -p
UNITYCHROOT=$HOME/Developer/unity/chroot
sudo mkarchroot $UNITYCHROOT/root base base-devel sudo
sudo arch-chroot $UNITYCHROOT
adduser pratik
pacman -S sudo git abs
sed -e 's/# %wheel ALL=(ALL) NOPASSWD: ALL/%wheel ALL=(ALL) NOPASSWD: ALL/' /etc/sudoers
usermod -G wheel pratik
su pratik
sudo abs
cd /home/pratik
cp -R PKGDIR /home/pratik #if you wanted to create a single package then copy it to the home directory and build it
cd PKGDIR 
makepkg -s

To create the Unity Packages, there’s a build script which was posted on the Arch Linux BBS and I have forked that gist.

The steps below show how to use the build script to create Unity Packages.

#Create Unity Packages from the PKGBUILDs created by Xiao-Long Chen
cd /home/pratik
Download the gist as unity-builder.sh
chmod +x unity-builder.sh
./unity-build.sh

The script isn’t without its faults and might not build smoothly for all packages. I’m still working on clearing out the kinks.

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer

The WordPress SEO Plugin by Yoast is a wonderful plugin for all practical purposes. However its got a minor glitch (or feature – depends on how you perceive it) that it adds extra columns to all post listings. Removing them is easy, but not many people venture into that part of WordPress – The Screen Options. Unselect the columns corresponding to WordPress SEO in screen options so that you don’t have to see them in post listings again. Screenshot Below

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git show <commit>

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git log --grep <string>

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer

The first thing I want to do when I get a new laptop is install Linux on it. I usually don’t have rewritable CD/DVD handy and have to depend on USB flash drives to install Linux. Surprisingly, documentation for Arch Linux was sparse on this subject. However I looked up how its done on Ubuntu and it worked seamlessly for Arch Linux.

Use LiLi to install Arch Linux on your laptop/desktop using a USB Flash drive. Lili is for the laptops/desktops which have Windows as the sole OS and want to install Linux on it.

1. Download LiLi from http://www.linuxliveusb.com/en/download
2. Download the latest Arch Linux ISO
3. Plug in a USB Flash key and fire up LiLi
4. Select the appropriate options and the ISO from the filesystem
5. Burn the ISO onto the USB flash key
6. Now reboot your system and make sure that you boot from the USB flash key (Use F12 key or update BIOS boot order)
7. Now follow the regular Arch Linux installation procedure to install it on your system

Detailed steps for using LiLi can be found here.

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer

Some might wonder, why would you do something like that? Install Unity on Arch Linux? Absolutely blasphemy. But really, I have fallen in love with this combination. Till a couple weeks back, I had been using Ubuntu for close to 4-5 years without experimenting with any other Linux distros. I usually resist the urge to install the alpha releases, but by the time the beta releases start coming out, I’m just itching to get hold of it, irrespective of how catastrophic it has turned out sometimes from the work perspective. So when Ubuntu 12.10 beta2 came out, I installed it. But I was sorely disappointed. Unity kept crashing for no good reason, generally not a very stable system. I know ‘beta’ versions aren’t supposed to be stable etc, but it shouldn’t crash as often as it did.

So I figured, if I want to live my life on the precipice of beta releases, why not use Arch Linux? If there’s such a thing as a stable bleeding edge distribution, then Arch Linux comes closest to that description. So I installed Arch Linux on my spanking new Thinkpad T430s (highly recommend T430s btw). But neither Gnome 3 nor KDE are my preferred desktop environments and I wanted Unity! I really do prefer Unity over Gnome and KDE these days (read more about it here). Thankfully somebody had already done all the hard work. And somebody and beautifully packaged it.

EDIT: So the above repository hasn’t been updated in a while, so I created one for myself. I’m hoping to keep it upto date with the packages on github. Troll me if I don’t.

So to install Unity, add the following lines to /etc/pacman.conf

 
[unity] 
Server = http://unity.humbug.in/$arch 

[unity-extra] 
Server = http://unity.humbug.in/extra/$arch 

and then

 # pacman -Suy # pacman -S $(pacman -Slq unity) 

Thats the core. Additionally if you just installed a fresh system, then you will need a display manager (gdm, lightdm). If you prefer the old fashioned way i.e. startx, then you could use the following xinitrc.

#!/bin/sh
#
# ~/.xinitrc
#
# Executed by startx (run your window manager from here)

if [ -d /etc/X11/xinit/xinitrc.d ]; then
  for f in /etc/X11/xinit/xinitrc.d/*; do
    [ -x "$f" ] && . "$f"
  done
  unset f
fi

exec unity

Have fun using Unity and Arch Linux!

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer

There’s a lot of criticism out there for the Unity Desktop Environment. Strangely I can’t echo the same sentiments. I quite like using Unity (mind you not Ubuntu). Here are a few reasons why and why not.

The Unity Launcher: I have always loved launchers. Back in the days, when I would change desktop environments every second day – fluxbox, gnome, kde, wmaker, etc, one thing was constant. I had gnome-panel (&) start from my xinitrc irrespective of what distribution I used. Also I have never been a fan of taskbars. The Unity launcher marries the traditional launcher with a highly usable taskbar. It had some usability issues when Ubuntu initially switched to Unity, but it’s almost perfect now with AppIndicator Support. I can have upto 15 applications open at the same time and it’s still a breeze to manage them.

Gnome Run Command: No don’t confuse this with the Ubuntu Dash (super key). This is the plain old ‘Alt + F2′ command. Its as good an application launcher as any. I use the ‘Ctrl + Space’ combination which is much more accessible than the ‘Alt + F2′ combo. Seriously, Linux distributions should take a cue from osx and change the default key bindings for the ‘Run’ command.

No Widgets BS: The KDE Plasma Workspaces and the OSX Dashboard are just a waste of valuable RAM. Who uses widgets? They are hidden beneath the application windows. I set them up, but I never use them. So good job for not plagiarizing a useless feature from osx.

Themes: Lot of awesome themes available for people like me who spend an eternity on eyecandy stuff.

Things that I don’t like:

Gwibber: I loved the Adobe Air version of Tweetdeck before Adobe decided to stop developing Adobe Air for Linux. I now use the Tweetdeck webapp. Not as good, but still much better than most linux twitter clients out there.

Empathy: Its good, but still needs more work. Looks ugly.

The last two reasons are more to do with the Gnome Bundle than Unity itself.

I tried Gnome 3 a couple times, but wasn’t happy with it. KDE is ugly. I dont think I’ll like Cinnamon, Mate either. I have seen the screenshots and I don’t like the ‘Start’ Menu.

I think I’m going to stick to Unity for the time being till there’s a better alternative.

Pratik Sinha - Embedded Linux and 802.11 Wireless Software Freelancer