Process Management III

Process Management III

1. FOREGROUND VS BACKGROUND

   • bg
     • Is a job control command that resumes suspended jobs while keeping them running in the background.
       • bg [job]
   • fg
     • In Linux, UNIX and any other POSIX-compliant operating system, the fg command continues a stopped job by running it in the foreground.
       • fg [ %job_id ]

2. PRIORITIES

   • COMMANDS
     • renice
       • renice alters the priority of running processes. It is similar to the nice command, but is used for processes that are already running.
         • renice [-n] priority
     • nice
       • Runs a command with a modified scheduling priority.
         • nice [OPTION] [COMMAND [ARG]...]

3. RUN LEVELS

   • An execution level is a preset operating state in an operating system similar to Unix
     • Level 0:
       • System halt; no activity, the system can be safely powered down.
     • Level 1:
       • Single user; rarely used.
     • Level 2:
       • Multiple users, no NFS (network filesystem); also used rarely.
     • Level 3:
       • Multiple users, command line interface; the standard runlevel for most Linux-based server hardware.
     • Level 4:
       • User-definable
     • Level 5:
       • Multiple users, GUI (graphical user interface); the standard runlevel for most Linuxbased desktop systems.
     • Level 6:
       • Reboot; used when restarting the system.
   • COMMAND: telinit

4. TOP

   • The "top" program provides a dynamic real-time view of a running system and can display summary information from it, as well as a list of processes or threads currently in use.
   • OPTIONS
     • -b
       • Starts top in 'Batch' mode, which could be useful for sending output from top to other programs or to a file.
     • -n
       • Specifies the maximum number of iterations, or frames, top should produce before ending.
     • -q
       • run with no delay
     • -s
       • Starts top with secure mode forced, even for root.
     • -d
       • Specifies the delay between screen updates
   • SINGLE-KEYS COMMANDS
     • h
       • generates a help screen
     • k
       • kill one process
     • n
       • change the priority of a process
     • q
       • exit
     • r
       • change the priority of a process
     • s
       • change the delay in seconds between updates