Login loop issue on Ubuntu

Had an issue with Ubuntu 14.04 version where in login into the system would result in the screen going through various screens and end up back at login page. I had previously had the same issue but was able to resolve it with the help of my friend. This time I thought I’d try to fix this myself and was able to faster than I thought.

Here’s how I resolved it after going through a few solutions :-

So basically lightdm is the display manager which comes by default with 14.04. So when you google for lightdm here’s what you find …

LightDM is an X display manager that aims to be lightweight, fast, extensible and multi-desktop. It uses various front-ends to draw login interfaces, also called Greeters.

Basically this package manages the login interface.To me that’s not a show stopper, in fact all my work starts after login.So I just thought I’d try another display manager. There are different display managers that work with ubuntu, another one being gdm. I just ran the following command to remove lightdm and install gdm.

CNTRL + ALT + F1 launches the terminal window even when user is’nt logged in.

sudo apt-get purge lightdm && sudo apt-get install gdm

This fixed my issue. Now I’m able to login to my machine without a prob. Case closed!

How to remove an application completely from linux

• apt-get remove packagename will remove the binaries, but not the configuration or data files of the package packagename. It will also leave dependencies installed with it on installation time untouched.
• apt-get purge packagename  or apt-get remove --purge packagenamewill remove about everything regarding the package packagename, but not the dependencies installed with it on installation. Both commands are equivalent.Particularly useful when you want to ‘start all over’ with an application because you messed up the configuration. However, it does not remove configuration or data files residing in users home directories, usually in hidden folders there. There is no easy way to get those removed as well.
• apt-get autoremove  removes orphaned packages, i.e. installed packages that used to be installed as an dependency, but aren’t any longer. Use this after removing a package which had installed dependencies you’re no longer interested in.
• aptitude remove packagename  or aptitude purge packagename (likewise)will also attempt to remove other packages which were required by packagename on but are not required by any remaining packages.

And many more exist. Lower-level dpkg-commands can be used (advanced), or GUI tools like Muon, Synaptic, Software Center, etc. There’s no single ‘correct way’ of removing applications or performing other tasks interacting with your package management.

The list you found are just examples. Make sure you understand the meanings and try out what it wants to do before accepting the action (you need to press Y before it actually performs the actions as proposed).

The asterisk version in the question is probably wrong; apt-get accepts a regular expression and not a glob pattern as the shell. So what happens with

sudo apt-get remove application*

is the following:

1. The shell tries to expand application* looking at the files in the current directory. If (as is normally the case) it finds nothing, it returns the glob pattern unaltered (supposing bashwith default behavior here — zsh will error out).
2. apt-get will remove the packages whose name contains a string that satisfies the regular expression application*, that is, applicatio followed by an arbitrary number of n: applicatio, application, applicationn, libapplicatio, etc.
3. To see how this can be dangerous, try (without root for double safety) apt-get -s remove "wine*" (-s will simulate the thing instead of doing it) — it will say is going to remove all packages that has “win” in their name and the dependant, almost the entire system…

Probably, the command that was meant is really

 sudo apt-get remove "^application.*"

(note the quotes and the dot) which will remove all packages whose name starts with application.

These commands,

sudo updatedb                  # 

are completely outside the scope of the package management. Do not remove files belonging to packages without using the package manager! It will get confused and is the wrong way to do things.

If you don’t know to which package a file belongs, try this:

dpkg -S /path/to/file

Checking Python Version on Ubuntu

$ readlink -f $(which python) | xargs -I % sh -c 'echo -n "%: "; % -V'

apt-get update only a single package

You just need to do apt-get install --only-upgrade <packagename>. This will upgrade only that single package, and only if it is installed.

If you wish to install the package if it doesn’t exist, or upgrade it if it does, you may leave out --only-upgrade.

sudo /etc/init.d/jenkins start not working

I had installed jenkins and builds were working fine.

Suddenly it stopped working. There is nothing in logs

I tried starting it, with the following command :-

sudo /etc/init.d/jenkins start

but still it’s not running

root@localhost:$# service jenkins restart
 * Restarting Jenkins Continuous Integration Server jenkins [ OK ] 

root@localhost:$# service jenkins status
Jenkins Continuous Integration Server is not running

After some googling I was able to get to run jenkins with the foll command :-

-Djava.awt.headless=true -jar /usr/share/jenkins/jenkins.war –webroot=/var/cache/jenkins/war –httpPort=8080

Still not able to get why the conventional Jenkins start command is not working. I’m working on ubuntu 14.04 version. So maybe there is some issue with Jenkins-Linux combination. To get it working is enough for the time being!