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Using the System Activity Reporter (sar)
Traducciones al EspañolEstamos traduciendo nuestros guías y tutoriales al Español. Es posible que usted esté viendo una traducción generada automáticamente. Estamos trabajando con traductores profesionales para verificar las traducciones de nuestro sitio web. Este proyecto es un trabajo en curso.
The System Activity Reporter (Sar) is a utility program for analyzing Linux system performance. Sar is a do-it-all monitoring tool that is part of the Sysstat system resource utilities package. Linux administrators should learn sar for its wide range of utility features. It measures CPU activity; memory/paging; interrupts; device load; network; process and thread allocation; and swap space utilization. Data is gathered in the /proc
filesystem. By default, sar collects data once for every 10-minute mark of each hour. This guide shows you how to install and configure sar on your Debian or Ubuntu Linux system. You also learn several useful commands to get you started collecting data about your Linux system’s activity.
Before You Begin
If you are using a Linode, make sure you run the steps in this section to configure your Linode, secure your server, and update your system’s packages.
If you have not already done so, create a Linode account and Compute Instance. See our Getting Started with Linode and Creating a Compute Instance guides.
Follow our Setting Up and Securing a Compute Instance guide to update your system. You may also wish to set the timezone, configure your hostname, create a limited user account, and harden SSH access.
Install and Configure sar
The open-source sar program is frequently used, but it’s not included in most Linux distributions. You must install it as part of the sysstat
package. This section shows you how to install sar on the Debian/Ubuntu Linux distributions.
Install sar, if it is not already installed on your system:
sudo apt-get install sysstat
Sar must be enabled before it can begin to collect data. Using your preferred text editor, open the
/etc/default/sysstat
configuration file, and change the value ofENABLED
totrue
.- File: /etc/default/sysstat
1 2 3 4 5 6 7 8 9
# # Default settings for /etc/init.d/sysstat, /etc/cron.d/sysstat # and /etc/cron.daily/sysstat files # # Should sadc collect system activity informations? Valid values # are "true" and "false". Please do not put other values, they # will be overwritten by debconf! ENABLED="true"
Other sar configuration data is kept in the files
/etc/cron.d/sysstat
and/etc/sysstat/sysstat
. The defaults should work well for you, but at some point you may want to change them. You can modify these files to update your settings. View your current sar settings to verify that the default values work for your desired configuration:sudo cat /etc/cron.d/sysstat sudo cat /etc/sysstat/sysstat
A typical
/etc/cron.d/sysstat
file resembles the following example:- File: /etc/cron.d/sysstat
1 2 3 4 5 6 7 8 9
# The first element of the path is a directory where the debian-sa1 # script is located PATH=/usr/lib/sysstat:/usr/sbin:/usr/sbin:/usr/bin:/sbin:/bin # Activity reports every 10 minutes everyday 5-55/10 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1 # Additional run at 23:59 to rotate the statistics file 59 23 * * * root command -v debian-sa1 > /dev/null && debian-sa1 60 2
The most commonly modified variable is the frequency setting for how often sar runs. It is controlled by the line:
- File: /etc/cron.d/sysstat
1 2 3
... 5-55/10 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1 ...
By default, the
debian-sa1
script runs every 10 minutes and collects sar data for historical reference. This data is written to the/var/log/sysstat/saXX
file, whereXX
is the day of the month. For example, if today is the 24th day of the month,sa1
writes the sar data to/var/log/sysstat/sa24
. To change the logging frequency to one minute, change5-55/10
to5-55/1
. To make it 2 minutes, change it to5/55/2
, and so on.Note Note that the/var/log/sysstat/saXX
is a binary file; a text editor can’t display these files properly.Frequently-used variables are set in the
/etc/sysstat/sysstat
file. These include the length of time log files should be kept; when log files should be compressed; and which compression algorithm should be used. The example below displays a typical/etc/sysstat/sysstat
file:# sysstat configuration file. See sysstat(5) manual page. # How long to keep log files (in days). # Used by sa2(8) script # If value is greater than 28, then use sadc's option -D to prevent older # data files from being overwritten. See sadc(8) and sysstat(5) manual pages. HISTORY=7 # Compress (using xz, gzip or bzip2) sa and sar files older than (in days): COMPRESSAFTER=10 # Parameters for the system activity data collector (see sadc(8) manual page) # which are used for the generation of log files. # By default contains the `-S DISK' option responsible for generating disk # statisitcs. Use `-S XALL' to collect all available statistics. SADC_OPTIONS="-S DISK" # Directory where sa and sar files are saved. The directory must exist. SA_DIR=/var/log/sysstat
Using sar
You can run sar both as an interactive program and in shell programs. There are two ways to run sar:
sar
followed by an option, without a saXX data file. This command displays the current day’s saXX data to the standard output (stdout
).sar
followed by an option, and additionally specifying a saXX data file using the-f
flag. This reports the performance data for that particular day.
Run sar using one of its collected data files. Ensure you replace the
sa24
with a sar data file that exists on your system. The number corresponds to the day of the month for which the data was collected. The example command displays the cumulative real-time CPU usage of all CPU cores on the 24th day of the current month:sudo sar -u -f /var/log/sysstat/sa24
The sar command returns a similar output:
Linux 4.19.0-13-amd64 (li900-72) 02/19/2021 _x86_64_ (2 CPU) 01:45:01 PM CPU %user %nice %system %iowait %steal %idle 01:55:01 PM all 0.13 0.00 0.07 0.01 0.01 99.78 02:05:01 PM all 0.13 0.00 0.06 0.00 0.01 99.80 Average: all 0.13 0.00 0.06 0.00 0.01 99.79
The data displayed is the following:
Linux 4.19.0-13-amd64: the Linux kernel version
(li900-72): The hostname where the sar data was collected
02/19/2021: The date when the sar data was collected
x86_64: The system architecture
(2 CPU): Number of CPU cores available
As is typical for powerful Linux utilities, you can get basic information or you can delve deep into the system. For example, you might want to know if your server is suffering from a spike in activity on a given date, during a particular time, or an earlier date.
Here are some simple, useful sar examples to illustrate the information you can gather.
Total CPU Usage
sar -u
: Displays CPU usage for the current day collected until that pointsar -u 1 3
: Displays real-time CPU usage every second, three timessar -u -f /var/log/sysstat/sa24
: Displays CPU usage for the month’s 24th day
For example, issuing sar -u
, displays the following output:
Linux 4.19.0-13-amd64 (li900-72) 02/19/2021 _x86_64_ (2 CPU)
01:45:01 PM CPU %user %nice %system %iowait %steal %idle
01:55:01 PM all 0.13 0.00 0.07 0.01 0.01 99.78
02:05:01 PM all 0.13 0.00 0.06 0.00 0.01 99.80
02:15:01 PM all 0.12 0.00 0.06 0.00 0.01 99.80
02:25:01 PM all 0.16 0.00 0.07 0.00 0.02 99.75
Average: all 0.14 0.00 0.06 0.00 0.01 99.78
View CPU Usage for Each CPU or Core
sar -P ALL
: Displays current day’s CPU usage by all coressar -P ALL 1 3
: Displays real-time CPU usage for all cores every second, three timessar -P 1
: Displays CPU usage for core number 1 for the current day. Cores are counted starting with 0.sar -P 1 1 3
: Displays real-time CPU usage for core number 1, every second, three times.sar -P ALL -f /var/log/sysstat/sa24
: Displays CPU usage broken down by all cores for the month’s 24th day.
For example, issuing sar -P ALL
, displays the following output:
Linux 4.19.0-13-amd64 (li900-72) 02/19/2021 _x86_64_ (2 CPU)
01:45:01 PM CPU %user %nice %system %iowait %steal %idle
01:55:01 PM all 0.13 0.00 0.07 0.01 0.01 99.78
01:55:01 PM 0 0.09 0.00 0.06 0.00 0.01 99.83
01:55:01 PM 1 0.18 0.00 0.08 0.01 0.01 99.73
01:55:01 PM CPU %user %nice %system %iowait %steal %idle
02:05:01 PM all 0.13 0.00 0.06 0.00 0.01 99.80
02:05:01 PM 0 0.16 0.00 0.07 0.00 0.01 99.76
02:05:01 PM 1 0.11 0.00 0.05 0.01 0.01 99.83
02:05:01 PM CPU %user %nice %system %iowait %steal %idle
02:15:01 PM all 0.12 0.00 0.06 0.00 0.01 99.80
02:15:01 PM 0 0.14 0.00 0.07 0.00 0.01 99.78
02:15:01 PM 1 0.11 0.00 0.05 0.01 0.01 99.83
02:15:01 PM CPU %user %nice %system %iowait %steal %idle
02:25:01 PM all 0.16 0.00 0.07 0.00 0.02 99.75
02:25:01 PM 0 0.18 0.00 0.07 0.00 0.03 99.72
02:25:01 PM 1 0.15 0.00 0.06 0.01 0.02 99.77
Average: CPU %user %nice %system %iowait %steal %idle
Average: all 0.14 0.00 0.06 0.00 0.01 99.78
Average: 0 0.14 0.00 0.07 0.00 0.02 99.77
Average: 1 0.14 0.00 0.06 0.01 0.01 99.79
Display Free, Available, and Used Memory
sar -r
: Displays data about the memory usage on your system. To view a detailed explanation for each column, issue theman sar
command, and search for each column name. For example, to learn aboutkbmemfree
, once you are viewing the sar manual pages, issue the/kbmemfree
command.sar -r 1 3
: Displays memory use for every second for the last three seconds.sar -r -f /var/log/sysstat/sa24
: Displays memory use on the 24th day of the current month.
For example, issuing sar -r
, displays the following output:
Linux 4.19.0-13-amd64 (li900-72) 02/19/2021 _x86_64_ (2 CPU)
01:45:01 PM kbmemfree kbavail kbmemused %memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
01:55:01 PM 3440536 3687488 56048 1.39 44168 442188 163488 3.58 153340 360960 16
02:05:01 PM 3442196 3689216 54436 1.35 44168 442236 160228 3.51 152160 360860 12
02:15:01 PM 3441952 3689160 54512 1.35 44180 442420 164400 3.60 151640 360928 28
02:25:01 PM 3441644 3688940 54528 1.35 44180 442488 162752 3.56 151552 361000 32
02:35:01 PM 3441456 3688816 54788 1.36 44180 442552 159448 3.49 152888 361060 16
Average: 3441557 3688724 54862 1.36 44175 442377 162063 3.55 152316 360962 21
Swap Space Used
sar -S
: Displays the current day’s swap space usage statistics. To view a detailed explanation for each column, issue theman sar
command, and search for each column name. For example, to learn aboutkbswpfree
, once you are viewing the sar manual pages, issue the/kbswpfree
command.sar -S 1 3
: Displays swap memory data for every second during the last three seconds.sar -S -f /var/log/sysstat/sa24
: Displays swap memory use on the 24th day of the current month.
For example, issuing sar -S
, displays the following output:
Linux 4.19.0-13-amd64 (li900-72) 02/19/2021 _x86_64_ (2 CPU)
01:45:01 PM kbswpfree kbswpused %swpused kbswpcad %swpcad
01:55:01 PM 524284 0 0.00 0 0.00
02:05:01 PM 524284 0 0.00 0 0.00
02:15:01 PM 524284 0 0.00 0 0.00
02:25:01 PM 524284 0 0.00 0 0.00
02:35:01 PM 524284 0 0.00 0 0.00
02:45:01 PM 524284 0 0.00 0 0.00
Average: 524284 0 0.00 0 0.00
I/O Transactions
sar -b
: Displays I/O transactions for the current day. To view a detailed explanation for each column, issue theman sar
command, and search for each column name. For example, to learn abouttps
, once you are viewing the sar manual pages, issue the/tps
command.sar -b 1 3
: Displays I/O transactions data for every second during the last three seconds.sar -b -f /var/log/sysstat/sa24
: Displays I/O transaction data on the 24th day of the current month.
For example, issuing sar -b
, displays the following output:
Linux 4.19.0-13-amd64 (li900-72) 02/19/2021 _x86_64_ (2 CPU)
01:45:01 PM tps rtps wtps bread/s bwrtn/s
01:55:01 PM 0.45 0.01 0.43 0.32 6.96
02:05:01 PM 0.36 0.00 0.36 0.00 5.25
02:15:01 PM 0.38 0.01 0.36 0.51 5.39
02:25:01 PM 0.37 0.00 0.37 0.00 5.47
02:35:01 PM 0.36 0.00 0.36 0.00 5.36
02:45:01 PM 0.47 0.11 0.35 6.33 5.41
Average: 0.40 0.02 0.37 1.19 5.64
Going further
There are numerous other sar commands, options, and flags. See the sar Linux manual pages for more information or issue the man sar
command to read the manual pages on your Linux system.
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