Advanced Unix 5 Sep 2005

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Advanced Unix - 5 Sep 2005
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Review Lab-1

• Using vi, change the max number of days a
  password can be used to 180
• Edit /etc/login.defs
• Change PASS_MAX_DAYS to 180
• Using vi change the minimum password length to 7
• Edit /etc/login.defs
• PASS_MIN_LEN to 7

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Review Lab-1

• Create a new group called students using the
  groupadd command
• (as root) groupadd students
• Change default group for new users to students
  using the useradd command
• (as root) useradd D g students
• Create an account for yourself

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Review Lab-1

• Create a new user with an expiration date of
  10/1/2005
• useradd e 10/01/2005 user1
• Look at /etc/shadow
• user1!!130270180713056
• The 13027 is the number of days from 1 Jan 1970
  and as is 13056

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Unix Epoch Date 1 Jan 1970

• The early Unix engineers picked that date
  arbitrarily, because they needed to set a uniform
  date for the start of time, and New Year's Day,
  1970 seemed most convenient.

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The 2038 Bug

• On Jan 19th 2038 many computers will encounter a
  date-related bug in their operating systems
  and/or in the applications they run. This can
  result in incorrect and wildly inaccurate dates
  being reported by the operating system and/or
  applications.
• reports of temporal echoes of the 2038 problem
  are already starting to appear in future date
  calculations for mortgages and vital statistics!
• See http//maul.deepsky.com/7Emerovech/2038.html
  
• Demo 2038ck.pl

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The 2038 Bug

• For more information see http//maul.deepsky.com/
  7Emerovech/2038.html
• Demo 2038ck.pl
• Some of you will still be members of the IT
  Community..Dont wait until the last minute!!!

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Review Lab-1

• Add your full name to the account you created for
  yourself using usermod
• usermod c ltyournamegt ltuseridgt
• Bottom Line Many, many ways to manage your
  users. Including the various GUI applications.

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Review Lab-1

• Did you make an ISO image? Mount it? Add to
  /etc/fstab?
• dd if/dev/cdrom of/home/ISO/fc4-dvd.iso
• mount /home/ISO/fc4-dvd.iso -t iso9660 o \
  loop/dev/loop1 /mnt/iso
• /home/ISO/fc4-dvd.iso /mnt/iso iso9660 \
  loop/dev/loop1,noauto

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System Profiles

• When a user logs in a system profile is
  established
• Sets environment variables
• I.e. PATH/bin/usr/bin
• Sets aliass
• I.e. alias rm rm i
• alias cp cp I
• alias cls clear

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System Profiles

• Various system-wide profiles
• /etc/profile (bourne shell)
• /etc/bashrc (bash shell)
• /etc/tcshrc (c-shell)
• User specific profiles (located in home dir)
• /.profile
• /.bashrc
• /.tcshrc

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Shell Scripts

• A shell script is a group of commands,
  funtctions, variables, etc., that can be run from
  the shell prompt (command line)
• Chapter 12 gives an overview of how shell scripts
  work and can be used.
• Automate system chores
• Application startup
• Even generate web pages
• http//www.wildbill.org/rose/fall05.cgi

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Shell Scripts (/etc/init.d/)

• Many of the startup scripts are located in the
  /etc/init.d directory
• Know and understand symbolic links
• A symbolic Link is where a file has one main
  name, but there's an extra entry in the file name
  table that refers any accesses back to the main
  name

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Symbolic Links

• Symbolic links are set up using the ln command
  with the -s option - so for exampleln -s
  filename1.txt filename2.txt

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System Boot Up (init)

• Chapter 12, Page 454
• Boot Sequence
• /etc/inittab file
• Run levels (page 457)
• run-level scripts (page 459)
• Be familiar with the table pages 460-461
• Demo /etc/init.d
• /etc/rc3.d
• /etc/rc5.d
• ..etc.