Linux Server Configuration

1.5.1 Process Monitoring: ps

The ps command gives a snapshot of the processes running on the system at a given moment in time. It normally shows a brief summary of each process. The command ps has many options. Some of the most commonly used are:

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  -a – Show processes owned by other users
  
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  -f – display process ancestors in a tree-like format
  
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  -u – use the user output format, showing user names and process start times
  

1.5.2 Process Monitoring: pstree

It also displays a snapshot of currently running processes. It always uses a tree like display similar to ps –f . Some of the most commonly used options for pstree are:

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  -a – displays command’s arguments
  
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  -c – don’t compact identical subtrees
  
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  -G – attempts to use terminal specific line-drawing characters
  
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  -h – highlights the ancestors of the current process
  
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  -n – sort processes numerically by pid, rather then alphabetically by name
  
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  -p – includes pid in the output
  

1.5.3 Process Monitoring: top

The top command shows full-screen, continuously updated snapshots of process activity. It wais for a short period of time between each snapshots to give the illusion of real-time monitoring. Processes are displayed in descending order of how much processor time they are using. It also displays system uptime, load average, cpu status and memory information. Some of the most commonly used options for top are:

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  -b – Batch mode — send snapshots to standard output
  
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  -n num – Exit after displaying num snapshots
  
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  -d delay – Wait delay seconds between each snapshot
  
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  -i – Ignore idle processes
  
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  –s – Disable interactive commands which could be dangerous the superuser