diff options
| author |   Patrick J Volkerding <volkerdi@slackware.com> | 2009-08-26 10:00:38 -0500 |
|---|---|---|
| committer |   Eric Hameleers <alien@slackware.com> | 2018-05-31 22:41:17 +0200 |
| commit | 5a12e7c134274dba706667107d10d231517d3e05 (patch) | |
| tree | 55718d5acb710fde798d9f38d0bbaf594ed4b296 /slackbook/html/process-control-ps.html | |
| download | current-5a12e7c134274dba706667107d10d231517d3e05.tar.gz current-5a12e7c134274dba706667107d10d231517d3e05.tar.xz | |
Slackware 13.0slackware-13.0
Wed Aug 26 10:00:38 CDT 2009
Slackware 13.0 x86_64 is released as stable! Thanks to everyone who
helped make this release possible -- see the RELEASE_NOTES for the
credits. The ISOs are off to the replicator. This time it will be a
6 CD-ROM 32-bit set and a dual-sided 32-bit/64-bit x86/x86_64 DVD.
We're taking pre-orders now at store.slackware.com. Please consider
picking up a copy to help support the project. Once again, thanks to
the entire Slackware community for all the help testing and fixing
things and offering suggestions during this development cycle.
As always, have fun and enjoy! -P.
Diffstat (limited to 'slackbook/html/process-control-ps.html')
| -rw-r--r-- | slackbook/html/process-control-ps.html | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/slackbook/html/process-control-ps.html b/slackbook/html/process-control-ps.html new file mode 100644 index 000000000..27b842686 --- /dev/null +++ b/slackbook/html/process-control-ps.html @@ -0,0 +1,243 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org" /> +<title>ps</title> +<meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" /> +<link rel="HOME" title="Slackware Linux Essentials" href="index.html" /> +<link rel="UP" title="Process Control" href="process-control.html" /> +<link rel="PREVIOUS" title="Foregrounding" href="process-control-foregrounding.html" /> +<link rel="NEXT" title="kill" href="process-control-kill.html" /> +<link rel="STYLESHEET" type="text/css" href="docbook.css" /> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> +</head> +<body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084" +alink="#0000FF"> +<div class="NAVHEADER"> +<table summary="Header navigation table" width="100%" border="0" cellpadding="0" +cellspacing="0"> +<tr> +<th colspan="3" align="center">Slackware Linux Essentials</th> +</tr> + +<tr> +<td width="10%" align="left" valign="bottom"><a href="process-control-foregrounding.html" +accesskey="P">Prev</a></td> +<td width="80%" align="center" valign="bottom">Chapter 11 Process Control</td> +<td width="10%" align="right" valign="bottom"><a href="process-control-kill.html" +accesskey="N">Next</a></td> +</tr> +</table> + +<hr align="LEFT" width="100%" /> +</div> + +<div class="SECT1"> +<h1 class="SECT1"><a id="PROCESS-CONTROL-PS" name="PROCESS-CONTROL-PS">11.3 <tt +class="COMMAND">ps</tt></a></h1> + +<p>So now you know how to switch back and forth between several processes that you've +started from the command line. And you also know that there are lots of processes running +all the time. So how do you list all of these programs? Well, you make use of the <tt +class="COMMAND">ps</tt>(1) command. This command has a lot of options, so we'll only +cover the most important ones here. For a complete listing, see the man page for ps. Man +pages are covered in-depth in <a href="help.html#HELP-SYSTEM-MAN">Section 2.1.1</a>.</p> + +<p>Simply typing <tt class="COMMAND">ps</tt> will get you a listing of the programs +running on your terminal. This incudes the foreground processes (which include whatever +shell you are using, and of course, <tt class="COMMAND">ps</tt> itself). Also listed are +backgrounded processes you may have running. Many times, that will be a very short +listing:</p> + +<div class="FIGURE"><a id="FIG-PROCESS-CONTROL-PS-SHORT" +name="FIG-PROCESS-CONTROL-PS-SHORT"></a> +<p><b>Figure 11-1. Basic <tt class="COMMAND">ps</tt> output</b></p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ps</kbd> + PID TTY TIME CMD + 7923 ttyp0 00:00:00 bash + 8059 ttyp0 00:00:00 ps +</pre> +</td> +</tr> +</table> +</div> + +<p>Even though this is not a lot of processes, the information is very typical. You'll +get the same columns using regular ps no matter how many processes are running. So what +does it all mean?</p> + +<p>Well, the <var class="LITERAL">PID</var> is the <span class="emphasis"><i +class="EMPHASIS">process ID</i></span>. All running processes are given a unique +identifier which ranges between 1 and 32767. Each process is assigned the next free PID. +When a process quits (or is killed, as you will see in the next section), it gives up its +PID. When the max PID is reached, the next free one will wrap back around to the lowest +free one.</p> + +<p>The <var class="LITERAL">TTY</var> column indicates which terminal the process is +running on. Doing a plain <tt class="COMMAND">ps</tt> will only list all the programs +running on the current terminal, so all the processes give the same information in the +TTY column. As you can see, both processes listed are running on <tt +class="FILENAME">ttyp0</tt>. This indicates that they are either running remotely or from +an X terminal of some variety.</p> + +<p>The <var class="LITERAL">TIME</var> column indicated how much CPU time the process has +been running. This is different from the actual amount of time that a process runs. +Remember that Linux is a multitasking operating system. There are many processes running +all the time, and these processes each get a small portion of the processor's time. So, +the TIME column should show much less time for each process than it actually takes to +run. If you see more than several minutes in the TIME column, it could mean that +something is wrong.</p> + +<p>Finally, the <var class="LITERAL">CMD</var> column shows what the program actually is. +It only lists the base name of the program, not any command line options or similar +information. To get that information, you'll need to use one of the many options to <tt +class="COMMAND">ps</tt>. We'll discuss that shortly.</p> + +<p>You can get a complete listing of the processes running on your system using the right +combination of options. This will probably result in a long listing of processes +(fifty-five on my laptop as I write this sentence), so I'll abbreviate the output:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ps -ax</kbd> + PID TTY STAT TIME COMMAND + 1 ? S 0:03 init [3] + 2 ? SW 0:13 [kflushd] + 3 ? SW 0:14 [kupdate] + 4 ? SW 0:00 [kpiod] + 5 ? SW 0:17 [kswapd] + 11 ? S 0:00 /sbin/kerneld + 30 ? SW 0:01 [cardmgr] + 50 ? S 0:00 /sbin/rpc.portmap + 54 ? S 0:00 /usr/sbin/syslogd + 57 ? S 0:00 /usr/sbin/klogd -c 3 + 59 ? S 0:00 /usr/sbin/inetd + 61 ? S 0:04 /usr/local/sbin/sshd + 63 ? S 0:00 /usr/sbin/rpc.mountd + 65 ? S 0:00 /usr/sbin/rpc.nfsd + 67 ? S 0:00 /usr/sbin/crond -l10 + 69 ? S 0:00 /usr/sbin/atd -b 15 -l 1 + 77 ? S 0:00 /usr/sbin/apmd + 79 ? S 0:01 gpm -m /dev/mouse -t ps2 + 94 ? S 0:00 /usr/sbin/automount /auto file /etc/auto.misc + 106 tty1 S 0:08 -bash + 108 tty3 SW 0:00 [agetty] + 109 tty4 SW 0:00 [agetty] + 110 tty5 SW 0:00 [agetty] + 111 tty6 SW 0:00 [agetty] + [output cut] +</pre> +</td> +</tr> +</table> + +<p>Most of these processes are started at boot time on most systems. I've made a few +modifications to my system, so your mileage will most likely vary. However, you will see +most of these processes on your system too. As you can see, these options display command +line options to the running processes. Recently, a kernel vulnerability in <tt +class="COMMAND">ptrace</tt> facilitated a fix which no longer shows command line options +for many running processes. These are now listed in brackets like PIDs 108 through 110. +It also brings up a few more columns and some other interesting output.</p> + +<p>First, you'll notice that most of these processes are listed as running on tty +“?”. Those are not attached to any particular terminal. This is most common +with daemons, which are processes which run without attaching to any particular terminal. +Common daemons are sendmail, BIND, apache, and NFS. They typically listen for some +request from a client, and return information to it upon request.</p> + +<p>Second, there is a new column: <var class="LITERAL">STAT</var>. It shows the status of +the process. <var class="LITERAL">S</var> stands for sleeping: the process is waiting for +something to happen. <var class="LITERAL">Z</var> stands for a zombied process. A zombied +processes is one whose parent has died, leaving the child processes behind. This is not a +good thing. <var class="LITERAL">D</var> stands for a process that has entered an +uninterruptible sleep. Often, these processes refuse to die even when passed a SIGKILL. +You can read more about SIGKILL later in the next section on <tt +class="COMMAND">kill</tt> . W stands for paging. A dead process is marked with an <var +class="LITERAL">X</var>. A process marked <var class="LITERAL">T</var> is traced, or +stopped. <var class="LITERAL">R</var> means that the process is runable.</p> + +<p>If you want to see even more information about the running processes, try this +out:</p> + +<table border="0" bgcolor="#E0E0E0" width="100%"> +<tr> +<td> +<pre class="SCREEN"> +<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ps -aux</kbd> + USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND + root 1 0.0 0.0 344 80 ? S Mar02 0:03 init [3] + root 2 0.0 0.0 0 0 ? SW Mar02 0:13 [kflushd] + root 3 0.0 0.0 0 0 ? SW Mar02 0:14 [kupdate] + root 4 0.0 0.0 0 0 ? SW Mar02 0:00 [kpiod] + root 5 0.0 0.0 0 0 ? SW Mar02 0:17 [kswapd] + root 11 0.0 0.0 1044 44 ? S Mar02 0:00 /sbin/kerneld + root 30 0.0 0.0 1160 0 ? SW Mar02 0:01 [cardmgr] + bin 50 0.0 0.0 1076 120 ? S Mar02 0:00 /sbin/rpc.port + root 54 0.0 0.1 1360 192 ? S Mar02 0:00 /usr/sbin/sysl + root 57 0.0 0.1 1276 152 ? S Mar02 0:00 /usr/sbin/klog + root 59 0.0 0.0 1332 60 ? S Mar02 0:00 /usr/sbin/inet + root 61 0.0 0.2 1540 312 ? S Mar02 0:04 /usr/local/sbi + root 63 0.0 0.0 1796 72 ? S Mar02 0:00 /usr/sbin/rpc. + root 65 0.0 0.0 1812 68 ? S Mar02 0:00 /usr/sbin/rpc. + root 67 0.0 0.2 1172 260 ? S Mar02 0:00 /usr/sbin/cron + root 77 0.0 0.2 1048 316 ? S Mar02 0:00 /usr/sbin/apmd + root 79 0.0 0.1 1100 152 ? S Mar02 0:01 gpm + root 94 0.0 0.2 1396 280 ? S Mar02 0:00 /usr/sbin/auto + chris 106 0.0 0.5 1820 680 tty1 S Mar02 0:08 -bash + root 108 0.0 0.0 1048 0 tty3 SW Mar02 0:00 [agetty] + root 109 0.0 0.0 1048 0 tty4 SW Mar02 0:00 [agetty] + root 110 0.0 0.0 1048 0 tty5 SW Mar02 0:00 [agetty] + root 111 0.0 0.0 1048 0 tty6 SW Mar02 0:00 [agetty] + [output cut] +</pre> +</td> +</tr> +</table> + +<p>That's a whole lot of information. Basically, it adds information including what user +started the process, how much of the system resources the process is using (the %CPU, +%MEM, VSZ, and RSS columns), and on what date the process was started. Obviously, that's +a lot of information that could come in handy for a system administrator. It also brings +up another point: the information now goes off the edge of the screen so that you cannot +see it all. The <var class="OPTION">-w</var> option will force <tt +class="COMMAND">ps</tt> to wrap long lines.</p> + +<p>It's not terribly pretty, but it does the job. You've now got the complete listings +for each process. There's even more information that you can display about each process. +Check out the very in-depth man page for <tt class="COMMAND">ps</tt>. However, the +options shown above are the most popular ones and will be the ones you need to use the +most often.</p> +</div> + +<div class="NAVFOOTER"> +<hr align="LEFT" width="100%" /> +<table summary="Footer navigation table" width="100%" border="0" cellpadding="0" +cellspacing="0"> +<tr> +<td width="33%" align="left" valign="top"><a href="process-control-foregrounding.html" +accesskey="P">Prev</a></td> +<td width="34%" align="center" valign="top"><a href="index.html" +accesskey="H">Home</a></td> +<td width="33%" align="right" valign="top"><a href="process-control-kill.html" +accesskey="N">Next</a></td> +</tr> + +<tr> +<td width="33%" align="left" valign="top">Foregrounding</td> +<td width="34%" align="center" valign="top"><a href="process-control.html" +accesskey="U">Up</a></td> +<td width="33%" align="right" valign="top"><tt class="COMMAND">kill</tt></td> +</tr> +</table> +</div> +</body> +</html> + |