Wednesday, August 13, 2014

Checking installed python modules

To check the installed python modules, there are 2 ways:

  1. run help('modules') command in the python shell, as below:
    • $ python
      Python 2.6.6 (r266:84292, Sep 11 2012, 08:28:27)
      [GCC 4.4.6 20120305 (Red Hat 4.4.6-4)] on linux2
      Type "help", "copyright", "credits" or "license" for more information.
      >>> help ('modules')
      
      Please wait a moment while I gather a list of all available modules...
      
      BaseHTTPServer      cProfile            imghdr              robotparser
      Bastion             cStringIO           imp                 rpm
      CDROM               cairo               imputil             rpmUtils
  2. and if you need to filter your search, running it directly from linux shell is the best, where you can use grep as below to filter your search, where -c is the flag for running a python command
    • $ python -c "help('modules')" | grep token
      _socket             future_builtins     pipes               token
      _sqlite3            gc                  pkg_resources       tokenize
      

Thursday, July 10, 2014

How to refresh your ldap name database in an ldap client

This is useful when, you have a server that is authenticated by ldap. After you have edited something in your ldap server, let's say you have edited a gid for a user, you would find out that it won't be reflected immediately on the client side. So in this case, how would you force your client to accept your newly changed settings? The answer is you need to restart nscd (name service cache daemon):

$ getent passwd pauld

pauld:x:1987:1987:Paul Daniels:/home/pauld:/bin/bash
So after you have made your changes in the server, let's say you want to change pauld's gid to 4000, run the above command again:

$ getent passwd pauld

pauld:x:1987:1987:Paul Daniels:/home/pauld:/bin/bash

Still the changes are not being reflected there. To solve this, simply restart nscd:

$ sudo /etc/init.d/nscd restart

Stopping nscd:                                             [  OK  ]

Starting nscd:                                             [  OK  ]

You should be seeing your change is now updated in the user database:

$ getent passwd pauld

pauld:x:1987:4000:Paul Daniels:/home/pauld:/bin/bash


PS: If for some reason you are still not seeing the new data, you can invalidate the nscd database by:
$ sudo nscd --invalidate=passwd 

where passwd is the name of the table name in nscd database. You can see all available table name in /var/db/nscd 

To look into what is the content of each table, please use strings command:
$ sudo strings /var/db/nscd/passwd




Tuesday, July 1, 2014

How to install custom upstart script

To install custom upstart script, please follow below steps (in this example, I'll be using a service call cat):

  1. Copy the script into /etc/init 
  2. To make upstart distinguish the new service, run: 
    • $ initctl reload-configuration 
  3. Check whether your script is already in upstart by running:
    • $ initctl list | grep cat 
      cat stop/waiting
  4. And you are done, you can check the status of your service by running:
    • $ service cat status 
      cat stop/waiting
  5. You can also do the same with start, stop and restart
    • $ service cat start
      * Starting cat .... [OK]
    • $ service cat stop
      * Stopping cat .... [OK]
    • $ service cat restart * Restarting cat .... [OK]

Thursday, June 5, 2014

How to check which package a file belongs to in Redhat or Centos

If the package is not installed, run below commands (in this example, i use mkpasswd as an example):
$ yum whatprovides "*/mkpasswd" 
OR
$ repoquery -q --file */mkpasswd


If the package is installed:
$ rpm -qf /usr/bin/mkpaswd 

Wednesday, May 28, 2014

How to install HP PSC 1410 printer on Precise Puppy Linux 5.7.1

After some hair pulling, I managed to get this printer installed. Below are the steps that I have taken:
  1. Turn on and connect the printer to the puppy machine
  2. Install hplip using puppy package manager. Run command "ppm" on terminal, and search for hplip.
  3. Make sure all dependencies are installed
  4. Launch cups by going to http://localhost:631
  5. Go to "Administration -> Printer -> Add printer" OR "Administration -> Printer -> Find new printer"
  6. Choose the printer with connection like "usb://HP/PSC%201400%20series?serial=CN5CDC60T004BM" with hplip in the name
  7. For Driver, choose "HP PSC 1400 Series, hpcups 3.12.9 (color, 2-sided printing)"
  8. Set default settings for the newly added printer by going to "Printer -> HP PSC 1410 -> Administration -> set default option". Print settings in application does not work.
  9. You are done..... Congratulation :)