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2

I know that niceness values are inherited from the niceness value of the parent process, but can I globally change the default niceness value for a particular user (myself).

In this case I have a small convenience server in mind, which is exclusively accessed via ssh. So, I think I could change my default shell from /bin/bash to /etc/bash5 while /etc/bash5 is this script:

#!/bin/sh
nice -n 5 /bin/bash

#file privileges: root:root 755

This strikes me as a terrible hack and error prone. There must be a better way.

I'm mostly interested in general solutions, that would also apply to a desktop/laptop system.

Edit: I tried the suggested limits.conf change, but it doesn't work as expected:

root@server# addgroup nice
root@server# adduser myself nice
root@server# echo '@nice soft nice 5' >> /etc/security/limits.conf

Then, from my client machine, I say

myself@client$ ssh server
myself@server$ sleep 1h &
myself@server$ htop

Now, the sleep process has an initial niceness value of 0, but if I change the value with F8 to 19 and then try to reduce it again with F7 it stops at 5.

Edit2: Solution

Instead of using the nice item in limits.conf, you actually have to use priority although it is counter-intuitive.

@nice soft priority 5
share|improve this question
    
Maybe put a renice -n 5 in your ~/.profile? – jw013 Aug 1 '12 at 18:00
    
@jw013: That's a better idea than my bash5 approach, I give you this. But it still breaks if I say ssh myserver -- somecommand doesn't it? – bitmask Aug 1 '12 at 18:02
    
@bitmask. I cannot reproduce your result for limits.conf. What's your output for ps -o pid,nice,cmd? – donothingsuccessfully Aug 3 '12 at 8:40
    
Please post solutions to your own problems as answers, rather than edits to your question. Thanks! (It's okay to provide your own answer to your own question.) – mattdm Aug 3 '12 at 19:14
    
On another note: this isn't what you asked, but you may find that cgroups provide more effective way of doing what (reduced priority for a certain user) you want than nice. – mattdm Aug 3 '12 at 19:16
up vote 5 down vote accepted

You can set the priority for a particular user in /etc/security/limits.conf file.

root       hard/soft     priority    10

This way u can set hard or soft limit for any particular user. So all the processes which this root user will start will have 5 as the default priority vale.

According to Wikipedia page:

The exact mathematical effect of setting a particular niceness value for a process depends on the details of how the scheduler is designed on that implementation of Unix.

Here is the snapshot which show the above procedure works:

This image is the screenshot of /etc/security/limits.conf file

This is snapshot of limits.conf file which show a line which i added at last like

root     hard     priority    15

After changing this, I started one ssh session using the command ssh root@localhost

enter image description here

This screenshot show last two lines which shows the nice value of last two processes -bash and sshd: root@pts/3 to be 15.

Edit

Here is the snapshot which shows that u can increase and decrease the niceness of a process enter image description here

Edit 2:

Here is the snapshort which shows that even normal user can change the niceness value.

enter image description here

share|improve this answer
    
I was talking about niceness, not priority. And as I said on the other answer, it doesn't seem to be accepted. Do I have to restart some daemon, or something? – bitmask Aug 1 '12 at 19:00
    
@bitmask: this one is working in mine...I am going to add snapshot in my answer wait... – pradeepchhetri Aug 1 '12 at 19:20
    
@bitmask: I have updated the answer with the snapshots..:) – pradeepchhetri Aug 1 '12 at 19:35
    
There is a difference between niceness and priority. I totally buy that you can change the hard priority, but I want to change the soft niceness. That's a different thing. – bitmask Aug 1 '12 at 19:38
    
@bitmask: Accirind to wiki page, A niceness of −20 is the highest priority and 19 or 20 is the lowest priority. So first u have to understand that niceness and priority are same..And I want to clear that these are hard and soft limits but its not like hard priority and soft niceness.. – pradeepchhetri Aug 1 '12 at 19:52
up vote 1 down vote

It looks like you can set a default priority for a user in limits.conf, with a line like:

username    soft  priority  5

See man limits.conf.

share|improve this answer
    
Sounds great. I just gave it a shot (using a special group though) @nice soft nice 5 but sshing into the machine and executing sleep 1h shows as having niceness 0 in htop. Any clue why the setting wasn't accepted? I'm on debian squeeze. – bitmask Aug 1 '12 at 18:46
    
what is @nice in the above comment..it should be the one of the user of ur linux machine. – pradeepchhetri Aug 1 '12 at 19:02
    
@pradeepchhetri: See the edit of my OP, please. It's a group name. – bitmask Aug 1 '12 at 19:10
    
why @ in front of group name while putting an entry in limits.conf file ? – pradeepchhetri Aug 1 '12 at 19:15
    
@pradeepchhetri: Because the man page says so? – bitmask Aug 1 '12 at 19:25

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