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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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SYSSTAT(5) Linux User's Manual SYSSTAT(5)
sysstat - sysstat configuration file.
This file is read by sa1(8) and sa2(8) shell scripts from the
sysstat's set of tools. It consists of a sequence of shell
variable assignments used to configure sysstat logging. The
variables and their meanings are:
COMPRESSAFTER
Number of days after which daily data files are to be
compressed. The compression program is given in the ZIP
variable.
DELAY_RANGE
Tell sa2 script to wait for a random delay in the indicated
range before running. This delay is expressed in seconds,
and is aimed at preventing a massive I/O burst at the same
time on VM sharing the same storage area. A value of 0
means that sa2 script will generate its reports files
immediately.
HISTORY
The number of days during which a daily data file or a
report should be kept. Data files or reports older than
this number of days will be removed by the sa2(8) shell
script. Data files and reports are normally saved in the
/var/log/sa directory, under the name saDD (for data files)
or sarDD (for reports), where the DD parameter indicates
the current day.
The number of files actually kept in the /var/log/sa
directory may be slightly higher than the HISTORY value due
to the way the sa2 script figures out which files are to be
removed (see below "How the sa2(8) script applies HISTORY
value"). Using a value of 28 keeps a whole month's worth of
data. If you set HISTORY to a value greater than 28 then
you should consider using sadc's option -D to prevent older
data files from being overwritten (see sadc(8) manual
page). In this latter case data files are named saYYYYMMDD
and reports sarYYYYMMDD, where YYYY stands for the current
year, MM for the current month and DD for the current day.
How the sa2(8) script applies HISTORY value
The sa2 script uses the find command with the -mtime option
to figure out which files are to be removed. The find
command interprets this value as "N 24 hour periods",
ignoring any fractional part. This means that the last
modified time of a given sa[r]DD data or report file, using
a HISTORY of 1, has to have been modified at least two days
ago before it will be removed. And for a HISTORY of 28 that
would mean 29 days ago.
To figure out how a HISTORY of 28 is applied in practice,
we need to consider that the sa2 script that issues the
find command to remove the old files typically runs just
before midnight on a given system, and since the first
record from sadc can also be written to the previous day's
data file (thereby moving its modification time up a bit),
the sa2 script will leave 30 files untouched. So for a
setting of 28, and counting the data file of the current
day, there will always be 31 files (or 30 files, depending
on the number of days in a month) in the /var/log/sa
directory during the majority of a given day. E.g.:
April 30th: 31 files (Apr 30th-1st, Mar 31th)
May 1st: 30 files (May 1st, Apr 30th-2nd)
Yet we can note the following exceptions (as inspected at
Noon of the given day):
February 28th: 31 files (Feb 28th-1st, Jan 31st, 30th &
29th)
March 1st: 30 files (Mar 1st, Feb 28th-2nd, Jan 31st &
30th)
March 2nd: 29 files (Mar 1st & 2nd, Feb 28th-3rd, Jan.
31st)
March 3rd: 28 files (Mar 1st-3rd, Feb 28th-4th)
March 4th - March 28th: 28 files
March 29th: 29 files
March 30th: 30 files
March 31st: 31 files
(Determining the number of files in March on a leap year is
left as an exercise for the reader).
Things are simpler if you use the sa[r]YYYYMMDD name
format. Apply the same logic as above in this case and you
will find that there are always HISTORY + 3 files in the
/var/log/sa directory during the majority of a given day.
REPEAT_HEADER
Maximum number of lines after which a header will be
inserted in the report generated by sa2 script. By default
there is only a header at the beginning of each report and
it is not repeated afterwards.
REPORTS
Set this variable to false to prevent the sa2 script from
generating reports (the sarDD files).
SA_DIR Directory where the standard system activity daily data and
report files are saved. Its default value is /var/log/sa.
SADC_OPTIONS
Options that should be passed to sadc(8). With these
options (see sadc(8) manual page), you can select some
additional data which are going to be saved in daily data
files. These options are used only when a new data file is
created. They will be ignored with an already existing one.
UMASK The sa1 and sa2 scripts generate system activity data and
report files in the /var/log/sa directory. By default the
files are created with umask 0022 and are therefore
readable for all users. Change this variable to restrict
the permissions on the files (e.g. use 0027 to adhere to
more strict security standards).
YESTERDAY
By default sa2 script generates yesterday's summary, since
the cron job usually runs right after midnight. If you want
sa2 to generate the summary of the same day (for example
when cron job runs at 23:53) set this variable to no.
ZIP Program used to compress data and report files.
/etc/sysconfig/sysstat
Sebastien Godard (sysstat <at> orange.fr)
sadc(8), sa1(8), sa2(8)
https://github.com/sysstat/sysstat
https://sysstat.github.io/
This page is part of the sysstat (sysstat performance monitoring
tools) project. Information about the project can be found at
⟨http://sebastien.godard.pagesperso-orange.fr/⟩. If you have a bug
report for this manual page, send it to sysstat-AT-orange.fr.
This page was obtained from the project's upstream Git repository
⟨https://github.com/sysstat/sysstat.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-04.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Linux AUGUST 2023 SYSSTAT(5)
Pages that refer to this page: sadf(1), sar(1), sa1(8), sa2(8), sadc(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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