How to use the command 'atop' (with examples)

The ‘atop’ command is a Linux system and process monitor. It provides detailed information about system resources, individual processes, disk usage, and more. This command is useful for monitoring system performance, analyzing resource utilization, and troubleshooting performance issues.

Use case 1: Start

Code:

atop

Motivation: Starting ‘atop’ without any arguments allows you to view a real-time summary of system resource utilization, including CPU usage, memory consumption, disk I/O, and network activity. This can be helpful in monitoring the overall health of the system and identifying any abnormalities or resource bottlenecks.

Example output:

ATOP - pre 11:57:13  interval: 10 seconds
PRC |  sys   0.05s |  user   0.70s  |  #proc   11   |  #trun    2  |  #tslpi   51  #tslpu    0
CPU |  sys       9% |  usr      90% |  irq       0% |  idle     1%  |  wait     0%  |  steal    0%
CPL |  avg1   0.97  |  avg5    0.98  |  avg15   0.87  |  csw   307687  |  intr   79235
MEM |  tot    7.6G  |  free    6.0G  |  cache 249.0M  |  buff  13.0M
SWP |  tot    4.0G  |  free    4.0G

Use case 2: Start and display memory consumption for each process

Code:

atop -m

Motivation: This command provides detailed information about memory consumption for each individual process running on the system. By monitoring memory usage, you can identify memory-intensive processes and analyze memory utilization patterns.

Example output:

PRC |  sys   0.00s |  user   0.07s  |  #proc   11   |  #trun    1  |  #tslpi   56  #tslpu    0
MEM |  tot    7.6G  |  free    6.0G  |  cache 248.4M  |  buff  13.0M
SWP |  tot    4.0G  |  free    4.0G

  PID  MINFLT  MAJFLT   VSTEXT  VSIZE  RSIZE  VGROW  RGROW  MEM  Command
  327    0.00    0.00     1736   824K   180K  +0.0K  +0.0K  0.2%  atd
  349    0.00    0.00     2550  1120K   288K  +0.0K  +0.0K  0.3%  rsyslogd
  ...

Use case 3: Start and display disk information

Code:

atop -d

Motivation: Monitoring disk activity can help identify performance and utilization issues related to storage. This command provides detailed information about disk I/O, including read and write rates, average queue length, and more. It can be useful in troubleshooting slow disk performance or identifying processes causing high disk activity.

Example output:

DSK |  sda   | busy     9% | read       3 | write   112 | avio    1 ms |
DSK |  sdb   | busy     0% | read       0 | write     0 | avio    0 ms |
DSK |  sdc   | busy     3% | read       2 | write    43 | avio    0 ms |
DSK |  sdd   | busy     0% | read       0 | write     0 | avio    0 ms |
DSK |  sde   | busy     0% | read       0 | write     0 | avio    0 ms |
... 

Use case 4: Start and display background process information

Code:

atop -c

Motivation: Background processes can have a significant impact on system performance and resource utilization. This command allows you to view detailed information about background processes, including their resource consumption, CPU usage, memory usage, and more. It can be helpful in identifying resource-intensive background processes and troubleshooting performance issues.

Example output:

PRC |  sys   0.08s |  user   3.28s  |  #proc  123   |  #trun   1   |  #tslpi  310  #tslpu    0
CPU |  sys       7% |  usr      93% |  irq       0% |  idle     2%  |  wait     0%  |  steal    0%
CPL |  avg1   0.99  |  avg5    0.98  |  avg15   0.98  |  csw   364643  |  intr   82224
...

Use case 5: Start and display thread-specific resource utilization information

Code:

atop -y

Motivation: Thread-specific resource utilization information can provide insights into the performance of multi-threaded applications and identify potential bottlenecks or resource contention issues. This command shows CPU usage, memory usage, and other resource metrics for each thread running on the system.

Example output:

CPU |  sys   0.00s  |  user   0.36s  |  #proc   15   |  #trun    1   |  #tslpi   54  #tslpu    0
CPL |  avg1   0.94   |  avg5    0.95   |  avg15   0.89  |  csw   232771  |  intr   57240
MEM |  tot    7.6G   |  free   6.0G   |  cache 244.6M  |  buff  13.0M
SWP |  tot    4.0G   |  free   4.0G

  PID  TID    CPU  prio             TIME  aff           SYS 10ms  1min        Saving Command
 3274 3274     0     -         1m1s814ms   -       0%    4    -  100%        - cron
   68   68    93     0      2m51s855ms   0       100%   5    -   90%        - kthreadd
...

Use case 6: Start and display the number of processes for each user

Code:

atop -au

Motivation: Tracking the number of processes for each user can help identify resource utilization patterns and detect any user-related resource constraints or abnormalities. This command provides a summary of the number of processes for each user currently running on the system.

Example output:

NUM |  root   |      20   |    -root-  |
NUM |  john   |       7   |    -john-  |
NUM |  jdoe   |      13   |    -jdoe-  |
...

Use case 7: Display help about interactive commands

Code:

atop -?

Motivation: This command displays help information about the interactive commands available within atop. It provides a list of available keyboard commands and their respective functions, allowing you to navigate and interact with the atop interface more efficiently.

Example output:

Description of interactive commands:

 a .............. invert the sort order
c .............. change display settings
d .............. disk subsystem subscreen
... 

Conclusion:

The ‘atop’ command is a powerful tool for monitoring system resources, analyzing process-level details, and troubleshooting performance issues in Linux. With its various command line options, it provides a flexible and comprehensive view of system metrics, making it a valuable tool for system administrators and performance analysts.