Category Archives: Linux

Ubuntu 12.10 Verdict

A Saturday, new Ubuntu in the Downloads folder. What is it that you expect a linux user to do?

I installed Ubuntu 12.10 on Lenovo X201. I had 10.10 installed previously. I decided not to upgrade, but to clean install. It didn’t give me upgrade options anyways.

Post installation, here are some of the things I faced / enjoyed

Bootup time almost 25 seconds, it was around 15-20s for 10.10. A BIG downside for this release!

The Dash feels much quicker. However the gnome-shell still feels snappy as opposed to dash

I fuckin love the WebApps concept in Unity – That has actually made me stick to Unity.

Search in Unity still makes you click – as opposed to gnome-shell – Search the right string and hit Enter. That doesn’t work in Unity

I hated the original Alt+Tab utility in Unity, so installed Compiz Configuration Settings Manager (originally ccsm – so don’t search for that in apt). I replaced it with Static Window Switcher. It worked but then strangely started showing bugs of ghost windows moving in and out of the gray bar – little distracting, but didn’t break anything. (I was too careless to resolve conflicts 😛 – Was that the reason ?)

I adore the complete integration of Social World into the top-right corner of Ubuntu. You name it, Gmail (the Web App of that one is “क्या बात !क्या बात !” It shows the unread mails in Inbox, TagX, TagY, all in that top-right corner dropdown). O… continuing with integration – Facebook, Twitter, Chat, etc. However I’m an old time user of Pidgin, and have tonnes of logs in Pidgin which I don’t want to lose. I have no idea how to make Pidgin as the default integrated chat client into GNOME3 and Unity alike. – Help would do. Thunderbird too integrated nicely since the last release.

Ubuntu – Amazon Nexus – Naaah ! Disabled the “Online Search Results” from the “Privacy” application

I’m not a big fan of the Dark Ambiance theme, but with the other themes support in terms of UI elements, logos, etc.. I’ve got to stick with Ambiance atleast for now. I would’ve preferred the old GTK2 based Clearlooks theme.

Score: 7/10 – All the marks getting lost for the tacky compiz and inability to change defaults easily without installing other apps.

Python 3.3 ipaddress module Awesomeness!

Python 3.3 was released yesterday, Sept. 29, 2012. It has a wonderfully geeky module for IP address.

Take a look at some of its usages..
Casting / Conversions

>>> str(ipaddress.IPv4Address('192.168.0.1'))
'192.168.0.1'
>>> int(ipaddress.IPv4Address('192.168.0.1'))
3232235521
>>> str(ipaddress.IPv6Address('::1'))
'::1'
>>> int(ipaddress.IPv6Address('::1'))
1

Arithmetic Operations

>>> IPv4Address('127.0.0.2') + 3
IPv4Address('127.0.0.5')
>>> IPv4Address('127.0.0.2') - 3
IPv4Address('126.255.255.255')
>>> IPv4Address('255.255.255.255') + 1
Traceback (most recent call last):
  File "", line 1, in 
ipaddress.AddressValueError: 4294967296 (>= 2**32) is not permitted as an IPv4 address

Wish I could code in Python 🙁

References

Tweaking Gnome3 / Fedora fonts like Ubuntu

Recently I installed Fedora 17. Font rendering in Fedora is somewhat unoptimized, thanks to many patent clad algorithms for rendering fonts. But you if you want the best, follow the steps below

  1. Enable RPM Fusion Repos
    rpm -ivh http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm

  2. Install freetype-freeworld package
    yum install freetype-freeworld

  3. Install gnome tweak tool
    yum install gnome-tweak-tool

  4. Tweak font rendering
    Open gnome-tweak-tool by typing “advanced settings”. Then set
    Hinting = Slight
    Antialiasing = Rgba

  5. Configure ~/.fonts.conf
    Please save the attached file as .fonts.conf in your home folder ( ie. /home/michael/.fonts.conf ). Note the file name is .fonts.conf with a period in the begining.
    fonts

Above will render fonts in the best possible way (Font Rendering is matter of preference – tweak around for yourself). Now any application, Google Chrome, Firefox, etc will render fonts in the same manner.

git remote branch cleanup

Many times in development, you pull in remote branches and over a period of time they become stale and get deleted on the server. But your local repository still keeps a reference of those. You need to clean stale / deleted remote branches on your local system

A simple command git remote prune helps.

Check which branches are dpresent on local and getting tracked

[rutu@ruturaj-vartak git-bisect-clone-2]$ git branch -av
* master                     43e538a merged
  test-branch                7c06ab4 added p
  remotes/origin/HEAD        -> origin/master
  remotes/origin/master      43e538a merged
  remotes/origin/test-branch 7c06ab4 added p

The above command git branch -av shows my branch test-branch is present on local and also present on remote

The following command shows which branches can be un-tracked/deleted on local (as they’ve been deleted on remote)

[rutu@ruturaj-vartak git-bisect-clone-2]$ git remote prune -n origin
Pruning origin
URL: file:///tmp/git-bisect-demo/
 * [would prune] origin/test-branch

The option -n is a dry-run option, showing which branches can be deleted/pruned on your local – as in this case test-branch. So we can go ahead and actually prune/cleanup

[rutu@ruturaj-vartak git-bisect-clone-2]$ git remote prune  origin
Pruning origin
URL: file:///tmp/git-bisect-demo/
 * [pruned] origin/test-branch

This cleans up my repository, a git branch -av will show my local status of branches.

[rutu@ruturaj-vartak git-bisect-clone-2]$ git branch -av
* master                43e538a merged
  test-branch           7c06ab4 added p
  remotes/origin/HEAD   -> origin/master
  remotes/origin/master 43e538a merged

The remote branch origin/test-branch has been knocked off locally, but the local branch test-branch remains. If wanted, we can clean-up the local as well

[rutu@ruturaj-vartak git-bisect-clone-2]$ git branch -d test-branch
Deleted branch test-branch (was 7c06ab4).

Git Bisect Tutorial

If you’re reading this, you’re an avid user of git, have made tons of commits and now you’re trying to find..

where the hell did the bug get introduced ?

git-bisect is a perfect tool to find that. To explain this awesome tool, I’ve created a small demo-repository which has only one file text.txt. In this file, I’ve incrementally added a, b, c, d and so on in each commit.

This is how my file text.txt looks like

[rutu@ruturaj-vartak git-bisect-demo]$ cat text.txt 
a
z
c
d
e
f
g
h
i
j
k
l
m
n

My git graph/log looks as below

If you are wondering what is “git g” its just an alias, following is my ~/.gitconfig

[rutu@ruturaj-vartak git-bisect-demo]$ cat ~/.gitconfig 
[alias]
	ci = commit
	st = status
	di = diff
	co = checkout
	k = !gitk --all
	g = log --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' --abbrev-commit --all
	d = difftool
[color]
	ui = true
[user]
	name = Ruturaj K. Vartak
	email = ruturaj@localhost
[diff]
	tool = vimdiff

To simulate a bug, somewhere in my code, I’ve replaced b with z. Now the with the current state of my code, I’ve got to find where and who introduced z in my code ?. Lets begin

git-bisect uses BST style division and search mechanism. So lets start.

  1. Start with a command,
    $ git bisect start
  2. Now its necessary to tell git, that where was the code good and bad. Obviously my code was good at revision b162893 and the HEAD or 20bacecis now bad. So ..
    1. $ git bisect good b162893
    2. $ git bisect bad 20bacec

    Now if you check the git graph…


    Notice how git has divided this history into 2 parts, and the HEAD now points to the partitioning commit fa70446.

    We can now cat the file and see if the bug was introduced.

    [rutu@ruturaj-vartak git-bisect-demo]$ cat text.txt 
    a
    b
    c
    d
    e
    f
    g
    h

    As you see, the bug still has not been introduced, so lets tell git that this commit is GOOD

  3. $ git bisect good
    Now lets look how the graph looks


    The head is now d126a8f, the half between 20bacec and fa70446 and lets cat our file, text.txt

    [rutu@ruturaj-vartak git-bisect-demo]$ cat text.txt 
    a
    z
    c
    d
    e
    f
    g
    h
    i
    j
    k

    Wohoo ! our bug is existing here, but we don’t know if it was added in b38e6d7, df4f3bc or the HEAD – d126a8f

  4. So we now tell git, that this is BAD commit
    $ git bisect bad
    Now lets look at our graph,


    It has made another division, HEAD now pointing to df4f3bc
  5. Lets see if this HEAD is GOOD or BAD,
    [rutu@ruturaj-vartak git-bisect-demo]$ cat text.txt 
    a
    b
    c
    d
    e
    f
    g
    h
    i
    j

    Hey !!! The bug is non-existent over here. Lets tell git the good news

    $ git bisect good
    And this is what it returns us back

    [rutu@ruturaj-vartak git-bisect-demo]$ git bisect good
    d126a8fbd75cbf5e015228f0411d205745a77e05 is the first bad commit
    commit d126a8fbd75cbf5e015228f0411d205745a77e05
    Author: Ruturaj K. Vartak 
    Date:   Sat Jul 7 12:32:04 2012 +0530
    
        added k
    
    :100644 100644 92dfa216416a1ac944633ab674568f8bae139d95 261ccd63acaba8ae42219a40579a9acec61f05d0 M	text.txt

    Since there were no commits between our last found BAD commit – d126a8f and our current HEAD – df4f3bc, git has determined the bug was introduced in d126a8f. It throws a complete info stack of what it has for that commit.

    This is how our final graph looks like


    Note: there is nothing left to check between d126a8f(BAD) and df4f3bc(GOOD)

  6. The last thing to do, is reset everything with
    git bisect reset
    Which leaves a clean state

    [rutu@ruturaj-vartak git-bisect-demo]$ git bisect reset
    Previous HEAD position was df4f3bc... added j
    Switched to branch 'master'
    [rutu@ruturaj-vartak git-bisect-demo]$ git g
    * 20bacec - (HEAD, master) added n (3 hours ago) 
    * c7edac3 - added m (3 hours ago) 
    * 83a34bc - added l (3 hours ago) 
    * d126a8f - added k (3 hours ago) 
    * df4f3bc - added j (3 hours ago) 
    * b38e6d7 - added i (3 hours ago) 
    * fa70446 - added h (3 hours ago) 
    * e4efb05 - added g (3 hours ago) 
    * 8fe6f2a - added f (3 hours ago) 
    * 96381ba - added e (3 hours ago) 
    * a07ce18 - added d (3 hours ago) 
    * 0b824e0 - added c (3 hours ago) 
    * b162893 - added b (3 hours ago) 
    * 7a60f8d - added a (3 hours ago)

Automating git bisect

Even though the above method looks easy, it could be painful if you’re going through 100s of commits. git has an automated way as well, using the git bisect run. Lets look how we can search our above code for bugs using the automated way

For git bisect run cmd, It needs an argument of a command that’ll do the search of bug in the script and return exit code 0 for GOOD or 1 for BAD.

Lets create a simple bug-finder.sh script that will grep for b, if grep finds, it’ll give exit status as 0, or else 1. We’ll capture the exit status of grep and throw as exit status of our script. We’ll place our bug-finder.sh in root folder of our repo.

Here is the script, Make sure you chmod +x bug-finder.sh

[rutu@ruturaj-vartak git-bisect-demo]$ cat bug-finder.sh 
#!/bin/bash
grep "b" text.txt
exitCode=$?
if [ $exitCode -eq 0 ]; then
	exit 0;
else
	exit 1;
fi

Lets begin, steps stay the same…

  1. $ git bisect start
  2. $ git bisect good b162893
  3. $ git bisect bad 20bacec
  4. Now, the magic –
    $ git bisect run ./bug-finder.sh
    The output is as follows – git successfully finding the bug
[rutu@ruturaj-vartak git-bisect-demo]$ git bisect run ./bug-finder.sh 
running ./bug-finder.sh
b
Bisecting: 2 revisions left to test after this (roughly 2 steps)
[d126a8fbd75cbf5e015228f0411d205745a77e05] added k
running ./bug-finder.sh
Bisecting: 0 revisions left to test after this (roughly 1 step)
[df4f3bc1e079bc75afd922726c719e16d1e4efdf] added j
running ./bug-finder.sh
b
d126a8fbd75cbf5e015228f0411d205745a77e05 is the first bad commit
commit d126a8fbd75cbf5e015228f0411d205745a77e05
Author: Ruturaj K. Vartak 
Date:   Sat Jul 7 12:32:04 2012 +0530

    added k

:100644 100644 92dfa216416a1ac944633ab674568f8bae139d95 261ccd63acaba8ae42219a40579a9acec61f05d0 M	text.txt
bisect run success

There it is, simply and cool. Ofcourse in this case a lot depends how and what you’ve coded in ur bug-finder.sh. A bug in this script will just fool git.

Update: You can clone the git-bisect-demo repository

git merge specific files from another branch or revision

You have a perfect git branch model, neatly dividing code between the release and the development or trunk branch. Now suddenly you realise that you need to use the file from the other branch. But you can’t merge the branch for that sake !! WTF !

git checkout !! help !

  1. Make sure the file that you want to pull is clean (ie. that file shouldn’t be shown as modified in git status)
  2. $ git checkout <other-branch-name>/<commit-hash> -- path/to/the/file

You can now checkout the branch’s HEAD or that hash’s state of the file into your current working directory. You can now play with your file, add, commit. Done !