Main Line Computer Users Group - Jan 2000 Issue 212

Passwords

The passwd command can be used to:

• Specify passwords for newly-created user accounts.
• Change an already-existing account's password.
• Change the password of the account you're logged into.

   [root@mlcug /root]# passwd name 
   New UNIX password: 
   Retype new UNIX password: 
   passwd: all authentication tokens 
           updated successfully

   [blarg@bigdog blarg] passwd 
   Changing password for name 
   (current) UNIX password: 
   New UNIX password: 
   Retype new UNIX password: 
   passwd: all authentication tokens 
           updated successfully

Shutting Down Your Linux System

Even though you may not be running any programs when you're ready to shutdown, that doesn't mean there's nothing running on your Linux system. To see what we mean, issue this command: ps ax

You may be working with files, and if you simply turn off your computer, these processes won't have a chance to close those files, and finish running in a clean manner. So when the time comes to shut your system down, you'll need some way of telling all these processes to finish up, and exit cleanly. And the way this is normally done is with the shutdown command. The shutdown command can only be run by root, so you'll need to either be logged in as root, or you can use the su command to 'become' root. The basic syntax for shutdown is:

shutdown

Please Note: The shutdown program resides in /sbin. If your PATH environment variable does not include /sbin, you will need to include the full path when you enter the command (i.e., /sbin/shutdown -h now). In most cases, you should include one of the following options:

* -h Halt system when shutdown ended
* -r Reboot system when shutdown ended

If you don't include either option, shutdown will bring your system into 'single user' mode. Unless you know why you want to be in single-user mode, you probably don't want to be in single-user mode. Simply enter the shutdown command (this time with -h or -r), and the shutdown will complete normally.

[Part 4 - next month]

Well, Time Magazine gave in to political correctness with the "Person of the Year" and the "Person of the Century" - both of whom happened to be men. But, with the latter, they tagged a a truly great one. Their words were:

"In a century that will be remembered foremost for its science and technology - - in particular for our ability to understand and then harness the forces of the atom and universe - - one person clearly stands out as both the greatest mind and paramount icon of our age: The kindly, absent-minded professor whose wild halo of hair, piercing eyes, engaging humanity and extraordinary brilliance made his face a symbol and his name a synonym for genius, Albert Einstein."

I can't add to that tribute...

Instead of just clicking a link, hold down the mouse button while on the link to reveal a 'contextual menu'. Use the Open Link in New Window choice, A LOT!, to make it real easy to view a variety of links while not having to go crazy with the Back button! [Randy Zeitman]

The contextual menu works on all sorts of goodies in Netscape:

Click and hold on a picture or graphic and you can Save or Copy. Click and hold on a link and you get Go To, Save as Bookmark, Copy Location, and more AWA New Window with Link.

by Emil Volcheck

In our December meeting, we had a give-and-take discussion on questions on the Y2K situation - left over from the last two meetings. We still had a few members who had not checked their systems - and, especially, applications - for Y2K suitability.

Since the various software authors have taken different routes to deal with Y2k, there is no one answer as to how to define the compliance of a specific application. In particular, since I think folks recognize that we are NOT going to give up 2-digit dates, the programmer has to decide how to implement that inevitability! And, they were by no means unanimous in the approach they took!!

So, when it comes to the specific applications that YOU USE, you need to (still) determine:

• what Y2K problems do they have,
• what Y2K fixes are available,
• what Y2K fixes have you done
• or what strategies will you use

All members are urged to come to the meeting and mutually share ewhat has transpired.

It is said that history repeats itself - but folks may have sort of doubted it with technology. But, it looks like it has come sound again:

Recently IBM announced their plan to build the superest, supercomputer - capable of performing a quadrillion floating point operations per second! It will consist of a conglomerate of a million simple microprocessors - with a simple instruction set and very speedy processing of same.

They noted that there will be only 57 instructions in the CPU's set - compared to hundreds for a typical Intel CPU, like a Pentium.

Do you recall that in the mid '70's, MOS Technology developed and sold the 6502 microprocessor that formed the foundation of the Apple and Commodore personal computers? Do you further recall that the 6502 was a simple microprocessor - with a simple instruction set and speedy processing of same? Do you further, further recall that the 6502 has 56 instructions in its set?

Well, what about history now?

by Emil Volcheck

Just a quicky update from my item of last month. At the present time, I now have 4 computers (3 PCs and a Mac) running the SETI softwarer - with unit processing times ranging from 14 hours/data packet to 42 hours.

On December 28th, they had processed 60 units of data. This puts me in the 88.2% level of SETI participants. Actually, I've processed over a 100 packets, but part of them were done on a different account - I'm now having all the computers putting their results in the same account.

You can check my progress at any time, by logging onto the website (setiathome.ssl.berkeley.edu), selecting User Accounts, then Account Status. At the dialogue box, enter: mtcuba@udel.edu. When you press return, you'll see my stats!!!

If you would like to learn more, ask at the next meeting - look over that. Or just download the software and GO!

By the time you read this, it will already be Y2K. I hope everyone survived the transition to the new century mark without mishap. Hopefully we'll be looking back on Y2K as mostly hype, and of very little substance.

Here's the corresponding NetMask & associated SubNet setup:

IP Address      NetMask           Subnet Addr    Broadcast Addr
-------------   ---------------   ------------   --------------
192.168.0.1     255.255.255.248   192.168.0.0    192.168.0.7
192.168.0.3     255.255.255.248   192.168.0.0    192.168.0.7
192.168.0.11    255.255.255.248   192.168.0.8    192.168.0.15
192.168.0.12    255.255.255.248   192.168.0.8    192.168.0.15

By varying the netmask, the number of computers that can be in the subnet can be changed. Acceptable netmask values include 0, 128, 192, 224, 240, 248, and 252. 254 is an unusable netmask value because it restrains a subnet to only 2 addresses, the Network Address & the Broadcast Address, and leaves no addresses for computers or other hardware. Can you determine why there are only a few acceptable netmask values? If you express them in binary form, I think you'll understand why.

When dividing a network into smaller groups when different interfaces are being used, the Subnet address corresponds to the Network address, and the subnet has a corresponding broadcast address at the top of each subnet.

So, how does the netmask get determined? Here's an example for the above situation for my LAN. We will work with the last number in the IP address. For example, the "?" in 192.168.0.? is the number we'll focus on. We'll also be converting this number to BINARY format.

1. In!BINARY, decimal 255 looks like 11111111; and decimal 0 looks like 00000000.
2. We want the binary form of the subnet address to end in "0" as in 11111110; and the broadcast address to end in "1" as in 00000001.
3. For each subnet, we need to allow enough addresses for the number of machines on the subnet by selecting a proper netmask.
4. The binary form of the netmask number will always be allocated 1's starting from the left position.

For the network example given above, the ethernet will accommodate IP addresses 192.168.0.0 to 192.168.0.7, including the subnet & broadcast addresses. In binary form the first and last available address numbers look like this:

0 0 0 0 0 0 0 1  = 1 decimal; host address of first computer on subnet
0 0 0 0 0 1 1 0  = 6 decimal; host address of last subnet computer
1 1 1 1 1 0 0 0  = 248 decimal in netmask 255.255.255.248
---------------
0 0 0 0 0 0 0 0  = 0; we AND the 6 (last machine in subnet) & 248
                      (Netmask) to get our subnet or network address.

For the AmigaLink subnet our IP addresses, including subnet & broadcast addresses, range from 192.168.0.8 to 192.168.0.15. In binary they look like this:

0 0 0 0 1 0 0 1  = 9 decimal; first computer host address available
0 0 0 0 1 1 1 0  = 14 decimal; last computer host address available
1 1 1 1 1 0 0 0  = 248 decimal in netmask of 255.255.255.248
---------------
0 0 0 0 1 0 0 0  = 8; we AND the 14 & 248 together to get our
                      subnet address.

TED'S MEANER A4000

After last month's meeting, Ted Dean and I spent some time working on his A4000 tower. For whatever reason, Ted's A4000 has not been the speediest of Amigas and he had been unable to get SHAPESHIFTER running since his "upgrade" to an A4000 with PPC.

I'm happy to report that Ted's machine now "flies", and that SHAPESHIFTER works again. How we got there I'm not quite sure, but we did re-install all the Phase5 software and upgraded to the latest library files using downloaded updates from the Phase5 Web site. Somewhere along the way, Ted's A4000 took on a new personality. Normal screen updates and directory accesses with the embedded 50MHz 68060 makes most Win95 400MHz PC's look like they're standing still when doing comparable tasks.

To enable SHAPESHIFTER to run with Ted's Phase5 hardware, we removed the PREPAREEMUL (it was already disabled since it slowed the system down) command from the beginning of his STARTUP-SEQUENCE file and substituted uhe following command using the Phase5 software:

SYS:CYBERTOOLS/CYBERMAP ROM PATCHMAC

We also added 3072 buffers to the existing 256 buffers on the partition containing the SHAPESHIFTER Mac HardFile. We used an ADDBUFFERS command in the USER-STARTUP file to make the additional allocation.

When we were done, SHAPESHIFTER was booting and running from the hardfile very nicely.

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    _   __      _  <>_  __      _
   /\\   |\    /|| ||  /  `    /\\
  /__\\  | \  / || || || ___  /__\\
 /    \\_|  \/  ||_||_ \__//_/    \\_
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If you have either software or hardware for your Amiga that has taken your fancy, please bring it to our attention. I'm sure your specific interests will be of interest to others. Let me know if this is the case at the next meeting, or leave me email on our BBS. Remember, a user group is only as rewarding as the sum of the efforts of its individual members.