Index

1. Fetchmail and NT (ems3)

• University mail server is ems3
  • a user joe has an account jbloggs on corporate
• also maintains a film mailing list
• requires three accounts
  • film@glam.ac.uk: post messages
  • film-request@glam.ac.uk: new users subscribe
  • film-admin@glam.ac.uk: users change passwords

2. Mailman

• handles mailing lists
  • web based and email based
• users subscribe, unsubscribe and post/receive email’s
  • by email
  • or by html/cgi pages and scripts
• view all articles on web, sort by author, subject, date

3. Mailman

• installs out of the box
• each mailing list requires
  • subject@glam.ac.uk mailbox
  • subject-admin@glam.ac.uk mailbox
  • subject-request@glam.ac.uk mailbox
• you need to decide the subject! and set them up accordingly
  • can be done via cgi/html

4. Fetchmail script

• set daemon 60  # fetchmail wakes up
                 # every 60 seconds
  
  #
  # joe’s email mailbox
  #
  poll ems3.glam.ac.uk protocol imap
       username jbloggs@corporate with
       password hidden, is joe here;
  
  #
  # films mailing list
  #
  
  
  poll ems3.glam.ac.uk protocol imap
       username film@corporate with
       password hidden, is film here;

• #
  #  and the admin names for the film
  #  mailing list
  #
  poll ems3.glam.ac.uk protocol imap
       username film-request@corporate
       with password hidden, is film-request here;
  poll ems3.glam.ac.uk protocol imap
       username film-admin@corporate
       with password hidden, is film-admin here;

5. Fetchmail script description

• NT domain is corporate
• usernames on ems3 do not need to be the same on a GNU/Linux box
• one fetchmail process running on GNU/Linux can handle many different user accounts
  • jbloggs, film, film-admin, film-request
• fetchmail allows optional syntax sugar
  • gui is available

6. Network File System (Advantages)

• NFS available on many operating systems
  • macos, UNIX, GNU/Linux, Free BSD, Solaris, PCs (MSDOS), VMS, OS/2
  • Novell and NT if you pay extra
• NFS built on top of Sun’s RPC (remote procedure call) mechanism
  • open standard, originally produced by Sun Micro-systems
  • uses RPC authentication

7. Network File System (Disadvantages)

• uses RPC authentication
  • easily spoofed
• information sent over network is not encrypted
  • data could be replaced

8. NFS Advantages

• stateless server and client
• server could be rebooted and user on client might be unaware of the reboot
• client/server distinction occurs at the application/user level not the system level
  • highly flexible, so we need to be disciplined in our administration/configuration

9. A typical GNU/Linux network

• 

• configuration is very flexible
  

10. GNU/Linux configuration

• flexibility could be a disadvantage as system administrators have to fight their way through many different options for various components just to perform simple operations
• it is possible that all machines are configured identically (except for their hostname, IP address etc)
  • and ghost a hard disk
• could configure the network operating systems so that all local disks can be seen by all machines

11. A typical GNU/Linux network

• alternatively machines could be very different (ie could build distinct client/server model similar to Novell)
• one machine has the common file system
• one machine has the system executables

12. Disadvantages of GNU/Linux configuration

• complexity
• flexibility requires system administrators be disciplined otherwise overall system may become unmanageable
  • when more machines are added
• harder to configure than other operating systems
  • getting better (GNU/Linux is embracing Gtk/Tcl/Python)
  • but complexity still remains
  • few graphical tools to identify installation errors
    • however the problems are being addressed

13. NFS configuration example

• can network file systems between different architectures
  • little endian, big endian - it makes no difference
• NFS design is built from three main parts: a protocol, a server and a client

• 

14. NFS configuration example

• components fit into the ISO-7 layer model

  

15. NFS example

• suppose we have two machines

• 

16. NFS configuration example

• our task is to allow machine floppsie see directory /home/fred on mcgreg
• tell floppsie where this directory resides
• need to tell mcgreg that floppsie is trusted

17. NFS configuration of floppsie

• edit /etc/fstab on floppsie and add the following line

• # remote fs    mount point  type   options
  mcgreg:/home  /home/mcgreg  nfs

18. NFS configuration of mcgreg

• need to tell machine mcgreg that /home is exported and that floppsie is allowed to see it
• edit /etc/exportfs on mcgreg and add the following line

• /home  193.63.128.0/255.255.255.0(rw) \
         193.63.152.84(rw)

• why do we use 193.63.152.84 rather than floppsie?
  

19. Laboratory work

• read about the program df using man
  • ie man df
• try running df and write down which file systems exist
• which file systems are networked (NFS)?
• continue working on your assignment

Index

This document was produced using groff-1.19.