Ubuntu Bootup Howto

Directories and Configs

• /etc/init is where the upstart init configs live. While they are not scripts themselves, they essentially execute whatever is required to replace sysvinit scripts.
• /etc/init.d is where all the traditional sysvinit scripts and the backward compatible scripts for upstart live. The backward compatible scripts basically run service myservice start instead of doing anything themselves. Some just show a notice to use the "service" command.
• /etc/init/rc-sysinit.conf controls execution of traditional scripts added manually or with update-rc.d to traditional runlevels in /etc/rc*
• /etc/default has configuration files allowing you to control the behaviour of both traditional sysvinit scripts and new upstart configs.

Using Services

Please note that generally, you can use either traditional sysvinit scripts and the methods of working with them as well as the new upstart configs and the command: "service" interchangeably. It is however recommended you use the new upstart methods which are both forward and backward compatible.

Starting a Service

# Traditional:
/etc/init.d/myservice start
# Upstart
service myservice start

Stopping a Service

# Traditional: 
/etc/init.d/myservice stop
# Upstart
service myservice stop

Getting a list of Services

# Traditional:
ls /etc/init.d
# Upstart: 
service --status-all

• Note: Upstart method will show both traditional and upstart services.
  
  

Adding a Service to Default runlevels

# Traditional
update-rc.d apache2 defaults

• Upstart: there is no concept of runlevels, everything is event driven with dependencies. You would add an upstart config to/etc/init and potentially source a config file in /etc/default to allow users to override default behaviour.

Removing a Service from Default runlevels

# Traditional - Something along the lines of
rm /etc/rc*/*myscript

• Upstart: If no config is available in /etc/default, edit config in /etc/init
  Show the List of Installed Packages on Ubuntu or Debian

  
  

  
  

  The command we need to use is dpkg –get-selections, which will give us a list of all the currently installed packages.

  $ dpkg --get-selections
  adduser                                         install
  alsa-base                                       install
  alsa-utils                                      install
  apache2                                         install
  apache2-mpm-prefork                             install
  apache2-utils                                   install
  apache2.2-common                                install
  apt                                             install
  apt-utils                                       install

  The full list can be long and unwieldy, so it’s much easier to filter through grep to get results for the exact package you need. For instance, I wanted to see which php packages I had already installed through apt-get:

  dpkg --get-selections | grep php

  libapache2-mod-php5                             install
  php-db                                          install
  php-pear                                        install
  php-sqlite3                                     install
  php5                                            install
  php5-cli                                        install
  php5-common                                     install
  php5-gd                                         install
  php5-memcache                                   install
  php5-mysql                                      install
  php5-sqlite                                     install
  php5-sqlite3                                    install
  php5-xsl                                        install

  For extra credit, you can find the locations of the files within a package from the list by using the dpkg -L command, such as:

  dpkg -L php5-gd
  /.
  /usr
  /usr/lib
  /usr/lib/php5
  /usr/lib/php5/20060613
  /usr/lib/php5/20060613/gd.so
  /usr/share
  /usr/share/doc
  /etc
  /etc/php5
  /etc/php5/conf.d
  /etc/php5/conf.d/gd.ini
  /usr/share/doc/php5-gd
  

  Now I can take a look at the gd.ini file and change some settings around…