UNIX for Dummies Questions & Answers

Hey All

i want to be able to run command line commands in a java program, ive heard about java runtime, am i on the right track?

Cheers for the help

Somehow the simple stuff seems to elude you, otherwise how comes you have questions? ;-))

Any details? Which OS does the client run? How fast do you want it to shut down? Fast? Faster? Fastest? Here are some some possibilities, sorted by velocity:

shutdown -h now
halt -q
print - "stand still!" > /dev/kmem

And which OS the server runs would help answering your question too, as every OS has its own facilities. There is a *little* difference between VMS, *ix, Plan 9, MVS, etc..

Btw., which authentication are you going to use? Kerberos? SSL? Nothing (like in: anybody can shut down everything at will?)

Sorry to put it so bluntly, but you don't come across like someone who has studied Computer Science almost to the end and is writing a thesis.

bakunin

LOL, I love UNIX but tbh we had a class on it in second year but that only covered scripting and simple dialog programs, as far as setting up servers and running all of the nitty gritty commands, we never did that, if we had I'd have learnt it. So my thesis is a bit of a trial by fire

The Server I wish to set up will be running Ubuntu 7.1 and the single client on the network ( for testing purposes will be running Windows XP SP2 )

In theory i want an option in my project program to be able to see graphically that client and then select options like restart, logout shutdown.

i know with Windows Server 2003 you just type shutdown "IP" -r or something similar

Also running the inline commands is done with runtime in java, i just want to know if anyone has made a java program that has done this and if they've encountered problems?

Ok, that is already some specification to work on.

On Unix you can remotely execute programs by opening a shell remotely and execute your command there. To open a shell you will have to use some sort of authentication. The least seucre is using "r-commands" (rexec, rlogin, rcmd, ...), which will require either paswword authentication (you don't want to do that in a program) or an ".rhosts" file in the home directory of the user you connect to.

Classical Unix would use Kerberos instead and there are "kerberized" variants of these r-commands, which will not rely on .rhosts-files, but on Kerberos-tickets. But these times are gone and Kerberos is not used widely any more.

Today the so-called SSL (Secure Socket Layer) protocol, a secured IP-protocol, is used mostly. There are some commands working on top of this protocol, namely scp (Secure CoPy) and ssh (Secure SHell). They authenticate either via password like the r-commands or via exchange of "keys" and "keyfiles". They are not easy to include into programs (ssh is somewhat difficult to script), but it can be done.

Recommended reading: manpages of rlogin/rexec/rcmd/rcp, Kerberos, ssh.

Each a book about all aspects of Kerberos and SSL is available from O'Reilly (and several others perhaps).

bakunin

1. You may find the following commands useful.

ssh / su / sudo / shutdown / reboot / uptime

2. Yes a JVM,

Code:

Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec(command);