Course
******

At CSL on 16th November 2004

Debian
======

- Stable
- Unstable

Gentoo
======

- http://www.gentoo.org/
- Portage
- Frequently updated
- Can emerge an old or a new version
- Can run different versions of the same package
- Can use one machine to compile the binaries and distribute to all the 
  other machines.

Choice of kernel
================

- 2.4 or 2.6
- We will use 2.6

Configuration often stored in ``/etc/conf.d/``

Initialisation is often stored in ``/etc/init.d/``

**Software RAID** - Try the following pages for help:

- http://www.gentoo.org/doc/en/gentoo-x86-tipsntricks.xml#software-raid
- http://forums.gentoo.org/viewtopic.php?p=1058579#1058579

Useful Commands
===============

Hold down Alt, SysRq while you type K, S, U, B

- ``K`` - Kills all running disks
- ``S`` - Synchronises drives
- ``U`` - umounts drives
- ``B`` - reboot

Note: On the Microsoft Natural Multimedia Keyboard you need to switch off
"F Lock", Hold down "Ctrl" and then press Alt SysRq etc...

Shift - *Page Up* and *Page Down* - will allow you to scroll back through
screens.

``cp``/``mv``

- Copy/Move

  ``chmod``

- Make something executable

  ::

    chmod +x <filename>
    chmod +r <filename> to make read only for the current user

- ``less``

  Check the system log:

  ::

    less /var/log/messages

- ``ls``

  Long listing of everything

  ::

    ls -la

  Sort by date/time

  ::

    ls -last

    <<<lsof>>>

- list open files - shows the port as well

  ::

    lsof | less 

- ``cron``

  To edit a crontab:

  ::

    crontab -e

- ``du``

  To find out how much disk space is used in the current folder and the ones
  below:

  ::

    du -ch

  Disk Usage - End of listing shows a summary

- ``grep``

  ::

    cat /var/log/messages | grep -i warning - -i = ignore case

- ``less``

  Similar to more on windows - but you can scroll back up!

  ``zless``

  Same as more - but will work on compressed files.

- ``locate``

  To install
  
  ::

    emerge slocate

  - a utility which will check the whole hard disk each day and store a map of
    the file system for quick searches
  - to update the locate database

  ::

    updatedb &

  to search the database

  ::

    locate <search> 

- ``lsof``

  Utilities for viewing which ports and network services are open/running

  ::

    lsof (list open files)
    lsof | grep -i listen
    cat /etc/services | grep pop

- ``make``

  the compiler will use inter process communications

  ::

    -pipe

  another register for the compiler - debug stack trace is not useful.

  ::

    -fomit-frame-pointer 
    nano -w /etc/make.conf.example
  
- We could compile binaries in Crediton, upload them to a web site and all
  sites could download from this location

  ::

    PORTAGE_BINHOST 

- ``mkdir``

  To make a directory.

- ``mount``

  - Mount a CDROM
  - If the file system you want is already mentioned in ``fstab`` then just:

    ::

      mount /mnt/cdrom

  - To unmount:

    ::

      umount /mnt/cdrom

  - If not in fstab

    ::

      cat /proc/devices

  - Use command completion to choose device:

    ::

      mount /dev/<device e.g. hdd> /mnt/cdrom

    ``hd`` = ide, ``b`` = scsi

- ``nano``

  - Is a clone of pico - easy to use - installed by default on Gentoo.
  - ``-w`` turns off word wrap
  - Always use ``-w`` to switch off word wrap 
  - NOTE - It saves the file word wrapped if you do not switch off word wrap.

- ``nmap``

  - Simple port scanning:

    ::

      nmap <ip address> -O

    To display OS details:

    ::

      -O 

    loopback - scan yourself or my ip address:

    ::

      nmap -sT -vvv 127.0.0.1 

- See ``lsof``

- ``ps``

  - processes
  - show original command line
  - ``a`` - all tasks
  - ``x`` - list services as well
  - ``u`` - all users

    ::

      ps faux | less - f
      kill -9 <pid>

- shows processes

  ::

    top

  - nice level - +19 is the lowest priority
  - ``wa`` is the CPU wait time - if it goes high then investigate faster hard
    drives
  - load average - usually around 2

  If a thread is blocking IO then it will add a whole 1 to the load average
  A zombie process could be a bad thing - Press the ``<``/``>`` keys to change
  the sort order, ``?`` to get help

- ``pstree``

  Gives an idea of what is currently running

- *Ctrl Z* pauses in the background
- ``bg`` lets the task continue in the background
- ``fg`` brings the task into the foreground
- ``jobs`` - will list what you have in the background
- ``%1`` to the first task
- To launch in the background add an ``&`` to the end of the command

- ``rmdir``
- ``screen``
  
  Allows you to control multiple screens on a remote Linux computer.  Like
  terminal server for Linux consoles.  emerge -v screen screen