limited cpu usage

Hi

I am kind of new to redhat security, and for my class, i need to give
users accounts to my server(i only have ssh open). But these students
run commands to make my cpu go at 100% so no one else can use it.

Is their a way to prevent this? I locked their account, but my
teacher would like use to give everyone access so locking them out is
not possible.

I looked into nice, but it seems to only work for commands..not for
all users.


thanks in advance for the help

take care

mark
Post a follow-up to

Mark wrote:

> Hi
>
> I am kind of new to redhat security, and for my class, i need to give
> users accounts to my server(i only have ssh open). But these students
> run commands to make my cpu go at 100% so no one else can use it.
>
> Is their a way to prevent this? I locked their account, but my
> teacher would like use to give everyone access so locking them out is
> not possible.
>

Have you looked for ulimit?

Wolfgang

>> I am kind of new to redhat security, and for my class, i need to give
>> users accounts to my server(i only have ssh open). But these students
>> run commands to make my cpu go at 100% so no one else can use it.
>
> Have you looked for ulimit?

Isn't that shell specific? i.e. can't a user still run a compiled program
that fork bombs or other wise consumes too many resources?

--
Jem Berkes
http://www.pc-tools.net/
Windows, Linux & UNIX software

Jem Berkes wrote:

>>> I am kind of new to redhat security, and for my class, i need to give
>>> users accounts to my server(i only have ssh open). But these students
>>> run commands to make my cpu go at 100% so no one else can use it.
>>
>> Have you looked for ulimit?
>
> Isn't that shell specific? i.e. can't a user still run a compiled program
> that fork bombs or other wise consumes too many resources?
>

No, first i have set ulimit -t 4 -H. Then I have started a program, that
uses a lot of cpu. After 4 seconds it will be killed.

In bash the command is ulimit. In csh/tcsh it is limit.

Wolfgang

>> Isn't that shell specific? i.e. can't a user still run a compiled
>> program that fork bombs or other wise consumes too many resources?
>>
>
> No, first i have set ulimit -t 4 -H. Then I have started a program,
> that uses a lot of cpu. After 4 seconds it will be killed.
>
> In bash the command is ulimit. In csh/tcsh it is limit.

Sounds good then, even though the shell still plays a major role. For
instance, I don't think this would stop someone from uploading a malicious
binary and executing it via CGI, or mail pipe, for instance.

Also, don't users have control over what their ulimit is? Is there a way to
prevent them from using the ulimit bash commands to change the settings?

--
Jem Berkes
http://www.pc-tools.net/
Windows, Linux & UNIX software