1 00:00:06,580 --> 00:00:11,385 We already talked about changing process priority while discussing top, but you don't need top 2 00:00:11,385 --> 00:00:16,190 to change process priority. Let's check out how to do it from the command line. 3 00:00:17,289 --> 00:00:20,440 By default, user processes are started with the same priority. 4 00:00:21,140 --> 00:00:24,989 And to adjust priorities, users can use the nice command. 5 00:00:26,399 --> 00:00:29,879 Non privileged users can only run processes with a lower priority. 6 00:00:30,519 --> 00:00:35,030 And privileged users can increase and decrease process priority as well. 7 00:00:35,689 --> 00:00:39,864 And the reach is from minus 20, which is the highest 8 00:00:39,864 --> 00:00:44,039 priority, to positive 19, which is giving you the lowest priority. 9 00:00:45,159 --> 00:00:50,579 And if you want to change the priority for currently running processes, you would use the renice command. 10 00:00:51,689 --> 00:00:53,719 We already have seen how to do it from top. 11 00:00:54,359 --> 00:00:57,649 Now let's change some priorities from the command line. 12 00:00:59,009 --> 00:01:02,240 So I'm going to use sudo nice help. 13 00:01:04,750 --> 00:01:10,549 Of course you don't need sudo to get help, but what I'm looking for is the syntax. 14 00:01:11,269 --> 00:01:15,510 So in the syntax you can see N N is the adjustment. 15 00:01:16,090 --> 00:01:21,200 Okay, so that means that I'm going To use 16 00:01:21,200 --> 00:01:26,310 sudo nice n10 dd if is dev 0 of 17 00:01:26,310 --> 00:01:31,420 is dev null running as a background. 18 00:01:32,099 --> 00:01:38,140 And let's also do another priority, same command, sudo nice n minus 10. 19 00:01:40,599 --> 00:01:44,510 And then still the best way to figure out would be top. 20 00:01:45,209 --> 00:01:47,980 But hey, can we also see it from another perspective? 21 00:01:49,000 --> 00:01:54,873 Figure it out. Psaox pipe grab DD and there we can 22 00:01:54,873 --> 00:02:00,746 see these DD processes to give you the cycles anyway. And 23 00:02:00,746 --> 00:02:06,620 that's why you can see them having the same CPU percentage. 24 00:02:07,379 --> 00:02:12,514 So the first DD process with PID 6351 has the PR 25 00:02:12,514 --> 00:02:17,649 set to 3030 and the nice value set to 10. 26 00:02:18,409 --> 00:02:22,384 So that's the friendly process. The other one has the PR set to 10 27 00:02:22,384 --> 00:02:26,360 and a nice value set to minus 10. And that's the unfriendly process. 28 00:02:27,539 --> 00:02:30,819 You can also change priority on running processes. 29 00:02:32,479 --> 00:02:38,159 So let me use dd if is dev0 of is 30 00:02:38,159 --> 00:02:43,840 device dev null again as a background job. Oops. 31 00:02:47,240 --> 00:02:53,689 So running jobs to verify that it is actually running. And I'm looking for job number five here. 32 00:02:54,310 --> 00:02:56,599 And that is the one that we're talking about. 33 00:02:57,419 --> 00:03:03,709 And what happens if we see it in top? Well, I can see 34 00:03:03,709 --> 00:03:10,000 the student job which is running with a CPU percentage of almost 100. 35 00:03:11,129 --> 00:03:16,623 Now if I want to change the priority for that, 36 00:03:16,623 --> 00:03:22,116 then first I need PS A and PS A is 37 00:03:22,116 --> 00:03:27,610 showing not enough information psaux Anyway, pipe grab dd. 38 00:03:28,110 --> 00:03:30,909 Now let's start again with if I want to change the priority. 39 00:03:32,469 --> 00:03:36,469 If I want to change the priority, I need to remember the process id 6685. 40 00:03:38,469 --> 00:03:44,034 Let me quit top and let me use renice 41 00:03:44,034 --> 00:03:49,599 minus n19 on pid 6685 there we can see 42 00:03:49,599 --> 00:03:55,164 that it has rescheduled the priority. The old priority 43 00:03:55,164 --> 00:04:00,729 was zero and the new priority is 19. 44 00:04:02,090 --> 00:04:04,949 That is how you can manage priority from the command line. 45 00:04:05,860 --> 00:04:10,014 Let's not forget to do a sudokel all DD because otherwise we 46 00:04:10,014 --> 00:04:14,169 have too many processes that are being quite busy on this system.