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Advanced Unix - 5 Sep 2005

Advanced Unix - 5 Sep 2005. 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. Review: Lab-1.

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Advanced Unix - 5 Sep 2005

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  1. Advanced Unix - 5 Sep 2005

  2. 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

  3. 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

  4. 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:!!:13027:0:180:7::13056: • The 13027 is the number of days from 1 Jan 1970 and as is 13056

  5. 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.

  6. 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

  7. 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…..Don’t wait until the last minute!!!

  8. Review: Lab-1 • Add your full name to the account you created for yourself using usermod usermod –c “<yourname>” <userid> • Bottom Line – Many, many ways to manage your users. Including the various GUI applications.

  9. 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

  10. System Profiles • When a user logs in a system profile is established • Set’s environment variables • I.e. PATH=/bin;/usr/bin; • Set’s alias’s • I.e. alias rm ‘rm –i’ alias cp ‘cp –I’ alias cls ‘clear’

  11. 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

  12. 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

  13. 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

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

  15. 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.

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