7.1. System Resources
Being able to monitor the performance of your system
is essential. If system resources become to low it can cause a lot of
problems. System resources can be taken up by individual users, or by
services your system may host such as email or web pages. The ability to
know what is happening can help determine whether system upgrades are needed,
or if some services need to be moved to another machine.
7.1.1. The top command.
The most common of these commands is top.
The top will display a continually updating report
of system resource usage.
# top
12:10:49 up 1 day, 3:47, 7 users, load average: 0.23, 0.19, 0.10
125 processes: 105 sleeping, 2 running, 18 zombie, 0 stopped
CPU states: 5.1% user 1.1% system 0.0% nice 0.0% iowait 93.6% idle
Mem: 512716k av, 506176k used, 6540k free, 0k shrd, 21888k buff
Swap: 1044216k av, 161672k used, 882544k free 199388k cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
2330 root 15 0 161M 70M 2132 S 4.9 14.0 1000m 0 X
2605 weeksa 15 0 8240 6340 3804 S 0.3 1.2 1:12 0 kdeinit
3413 weeksa 15 0 6668 5324 3216 R 0.3 1.0 0:20 0 kdeinit
18734 root 15 0 1192 1192 868 R 0.3 0.2 0:00 0 top
1619 root 15 0 776 608 504 S 0.1 0.1 0:53 0 dhclient
1 root 15 0 480 448 424 S 0.0 0.0 0:03 0 init
2 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 keventd
3 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 kapmd
4 root 35 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd_CPU0
9 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 bdflush
5 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 kswapd
10 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 kupdated
11 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 mdrecoveryd
15 root 15 0 0 0 0 SW 0.0 0.0 0:01 0 kjournald
81 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 khubd
1188 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 kjournald
1675 root 15 0 604 572 520 S 0.0 0.1 0:00 0 syslogd
1679 root 15 0 428 376 372 S 0.0 0.0 0:00 0 klogd
1707 rpc 15 0 516 440 436 S 0.0 0.0 0:00 0 portmap
1776 root 25 0 476 428 424 S 0.0 0.0 0:00 0 apmd
1813 root 25 0 752 528 524 S 0.0 0.1 0:00 0 sshd
1828 root 25 0 704 548 544 S 0.0 0.1 0:00 0 xinetd
1847 ntp 15 0 2396 2396 2160 S 0.0 0.4 0:00 0 ntpd
1930 root 24 0 76 4 0 S 0.0 0.0 0:00 0 rpc.rquotad |
The top portion of the report lists information such as
the system time, uptime, CPU usage, physical ans swap memory usage,
and number of processes. Below that is a list of the processes sorted
by CPU utilization.
You can modify the output of top while
is is running. If you hit an i, top will no longer
display idle processes. Hit i again to see them
again. Hitting M will sort by memory usage,
S will sort by how long they processes have been
running, and P will sort by CPU usage again.
In addition to viewing options, you can also modify processes
from within the top command. You can use
u to view processes owned by a specific user,
k to kill processes, and r to
renice them.
For more in-depth information about processes you can look in
the /proc filesystem. In the /proc
filesystem you will find a series of sub-directories with numeric names.
These directories are associated with the processes ids of currently
running processes. In each directory you will find a series of files
containing information about the process.
YOU MUST TAKE EXTREME CAUTION TO NOT MODIFY THESE FILES, DOING
SO MAY CAUSE SYSTEM PROBLEMS!
7.1.2. The iostat command.
The iostat will display the current CPU load
average and disk I/O information. This is a great command to monitor
your disk I/O usage.
# iostat
Linux 2.4.20-24.9 (myhost) 12/23/2003
avg-cpu: %user %nice %sys %idle
62.09 0.32 2.97 34.62
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
dev3-0 2.22 15.20 47.16 1546846 4799520 |
For 2.4 kernels the devices is names using the device's major
and minor number. In this case the device listed is
/dev/hda. To have
iostat print this
out for you, use the
-x.
# iostat -x
Linux 2.4.20-24.9 (myhost) 12/23/2003
avg-cpu: %user %nice %sys %idle
62.01 0.32 2.97 34.71
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util
/dev/hdc 0.00 0.00 .00 0.00 0.00 0.00 0.00 0.00 0.00 2.35 0.00 0.00 14.71
/dev/hda 1.13 4.50 .81 1.39 15.18 47.14 7.59 23.57 28.24 1.99 63.76 70.48 15.56
/dev/hda1 1.08 3.98 .73 1.27 14.49 42.05 7.25 21.02 28.22 0.44 21.82 4.97 1.00
/dev/hda2 0.00 0.51 .07 0.12 0.55 5.07 0.27 2.54 30.35 0.97 52.67 61.73 2.99
/dev/hda3 0.05 0.01 .02 0.00 0.14 0.02 0.07 0.01 8.51 0.00 12.55 2.95 0.01 |
The iostat man page contains a detailed
explanation of what each of these columns mean.
7.1.3. The ps command
The ps will provide you a list of
processes currently running. There is a wide variety of options
that this command gives you.
A common use would be to list all processes currently running.
To do this you would use the ps -ef command.
(Screen output from this command is too large to include, the following
is only a partial output.)
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 Dec22 ? 00:00:03 init
root 2 1 0 Dec22 ? 00:00:00 [keventd]
root 3 1 0 Dec22 ? 00:00:00 [kapmd]
root 4 1 0 Dec22 ? 00:00:00 [ksoftirqd_CPU0]
root 9 1 0 Dec22 ? 00:00:00 [bdflush]
root 5 1 0 Dec22 ? 00:00:00 [kswapd]
root 6 1 0 Dec22 ? 00:00:00 [kscand/DMA]
root 7 1 0 Dec22 ? 00:01:28 [kscand/Normal]
root 8 1 0 Dec22 ? 00:00:00 [kscand/HighMem]
root 10 1 0 Dec22 ? 00:00:00 [kupdated]
root 11 1 0 Dec22 ? 00:00:00 [mdrecoveryd]
root 15 1 0 Dec22 ? 00:00:01 [kjournald]
root 81 1 0 Dec22 ? 00:00:00 [khubd]
root 1188 1 0 Dec22 ? 00:00:00 [kjournald]
root 1675 1 0 Dec22 ? 00:00:00 syslogd -m 0
root 1679 1 0 Dec22 ? 00:00:00 klogd -x
rpc 1707 1 0 Dec22 ? 00:00:00 portmap
root 1813 1 0 Dec22 ? 00:00:00 /usr/sbin/sshd
ntp 1847 1 0 Dec22 ? 00:00:00 ntpd -U ntp
root 1930 1 0 Dec22 ? 00:00:00 rpc.rquotad
root 1934 1 0 Dec22 ? 00:00:00 [nfsd]
root 1942 1 0 Dec22 ? 00:00:00 [lockd]
root 1943 1 0 Dec22 ? 00:00:00 [rpciod]
root 1949 1 0 Dec22 ? 00:00:00 rpc.mountd
root 1961 1 0 Dec22 ? 00:00:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
root 2057 1 0 Dec22 ? 00:00:00 /usr/bin/spamd -d -c -a
root 2066 1 0 Dec22 ? 00:00:00 gpm -t ps/2 -m /dev/psaux
bin 2076 1 0 Dec22 ? 00:00:00 /usr/sbin/cannaserver -syslog -u bin
root 2087 1 0 Dec22 ? 00:00:00 crond
daemon 2195 1 0 Dec22 ? 00:00:00 /usr/sbin/atd
root 2215 1 0 Dec22 ? 00:00:11 /usr/sbin/rcd
weeksa 3414 3413 0 Dec22 pts/1 00:00:00 /bin/bash
weeksa 4342 3413 0 Dec22 pts/2 00:00:00 /bin/bash
weeksa 19121 18668 0 12:58 pts/2 00:00:00 ps -ef |
The first column shows who owns the process. The second
column is the process ID. The Third column is the parent process
ID. This is the process that generated, or started, the process.
The forth column is the CPU usage (in
percent). The fifth column is the start time, of date if the process
has been running long enough. The sixth column is the tty associated
with the process, if applicable. The seventh column is the cumulitive
CPU usage (total amount of CPU time is has used while running). The
eighth column is the command itself.
With this information you can see exacly what is running on
your system and kill run-away processes, or those that are causing
problems.
7.1.4. The vmstat command
The vmstat command will provide a report
showing statistics for system processes, memory, swap,
I/O, and the CPU. These statistics are generated using data from the
last time the command was run to the present. In the case of the
command never being run, the data will be from the last reboot until
the present.
# vmstat
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
0 0 0 181604 17000 26296 201120 0 2 8 24 149 9 61 3 36 |
The following was taken from the
vmstat man page.
FIELD DESCRIPTIONS
Procs
r: The number of processes waiting for run time.
b: The number of processes in uninterruptable sleep.
w: The number of processes swapped out but otherwise runnable. This
field is calculated, but Linux never desperation swaps.
Memory
swpd: the amount of virtual memory used (kB).
free: the amount of idle memory (kB).
buff: the amount of memory used as buffers (kB).
Swap
si: Amount of memory swapped in from disk (kB/s).
so: Amount of memory swapped to disk (kB/s).
IO
bi: Blocks sent to a block device (blocks/s).
bo: Blocks received from a block device (blocks/s).
System
in: The number of interrupts per second, including the clock.
cs: The number of context switches per second.
CPU
These are percentages of total CPU time.
us: user time
sy: system time
id: idle time
7.1.5. The lsof command
The lsof command will print out a list of
every file that is in use. Since Linux considers everythihng a file,
this list can be very long. However, this command
can be useful in diagnosing problems. An example of this is if you wish
to unmount a filesystem, but you are being told that it is in use. You
could use this command and grep for the name of the
filesystem to see who is using it.
Or suppose you want to see all files in use by a particular process.
To do this you would use lsof -p -processid-.
7.1.6. Finding More Utilities
To learn more about what command line tools are available, Chris
Karakas has wrote a reference guide titled GNU/Linux
Command-Line Tools Summary. It's a good resource for learning
what tools are out there and how to do a number of tasks.
