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Chapter 21:
Introduction to Linux Systems Administration
Heading
Description
USER
The user name of the owner for each process.
PID
The process identification number.
%CPU
The percentage of the CPU taken up by a process. Remember that
for a system with multiple processors, this column will add up to
greater than 100 percent!
%MEM
The percentage of memory taken up by a process.
VSZ
The amount of virtual memory that a process is taking.
RSS
The amount of actual (resident) memory that a process is taking.
TTY
The controlling terminal for a process. A question mark (?) means
that the process is no longer connected to a controlling terminal.
STAT
The process's state. S is sleeping. (Remember that all processes
that are ready to run--that is, those that are being multitasked
while the CPU is momentarily focused on another process--will
be asleep). R means that the process is actually on the CPU. D is an
uninterruptible sleep (usually I/O-related). T means that a process
is being traced by a debugger or has been stopped. Z means
that the process has gone zombie. Each process state can have a
modifier suffixed to it: W, <, N, or L. W means that the process has
no resident pages in memory (it has been completely swapped out).
< indicates a high-priority process. N indicates a low-priority task.
L indicates that some pages are locked into memory (which usually
signifies the need for real-time functionality).
START
The date that the process was started.
TIME
The amount of time the process has spent on the CPU.
COMMAND The name of the process and its command-line parameters.
Table 21-11.
ps Command Output
DEFINE-IT! Going Zombie
Going zombie means one of two things: either the parent process has not
acknowledged the death of its child process using the wait system call or the
parent was improperly killed and thus the init process cannot reap the child
until the parent is completely killed. A zombied process usually indicates poorly
written software.
Summary :
353 Chapter 21: Introduction to Linux Systems Administration Heading Description USER The user name of the owner for each process. Going Zombie Going zombie means one of two things: either the parent process has not acknowledged the death of its child process using the wait system call or the parent was improperly killed and thus the init process cannot reap the child until the parent is completely killed.
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