Monitoring Activity

• Wikipedia - Zombie Process
• Wikipedia - ps
• Wikipedia - Process_state

Managing shell jobs

• Use command & to start a job in the background
• To move a job to the background
  • First, stop it by typing Ctrl-z
  • Next, type bg to move it to the background
  • Use fg to bring it back to the foreground
• Use jobs for a complete overview of running jobs

Observing process information with ps

• The ps command has two different dialects: BSD and System V
  • In BSD, options do not have a leading -
  • In System V, options do have a leading -
• ps shows an overview of current processes
• ps aux shows an overview of all processes
• ps -fax shows process forks
• ps -fU {user} shows all processes owned by user
• ps -f --forest -C sshd shows sshd and all the children
• ps L lists format specifiers
• ps -L shows threads
• ps -eo pid,ppid,user,cmd example of using format specifiers to get what you want

Monitoring memory usage

• Use free -m to get details about current memory usage
• More detailed memory information is in /proc/meminfo

Write cache

• While writing files, a write cache (buffer) is used
• This write cache is periodically committed to disk by the pdflush kernel thread
• As a result, after committing a file write, it’s not immediately secure
• To ensure that a file is committed to disk immediately, use the sync command

Observing CPU load

• CPU load is checked through uptime

Monitoring activity with top

• top is a dashboard that allows you to monitor current system activity
• Press f to show and select from available display fields
• Press M to filter on memory usage
• Press W to save new display settings
• Press 1 to show the usage stats for all CPUs

Lab Exercise

1. Use the appropriate utilities to find out if your machine performance is in good shape

Solution

1. Use top