SYSSTAT(5) Linux User's Manual SYSSTAT(5)
NAME
sysstat - sysstat configuration file.
DESCRIPTION
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 com-
pressed. 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/sysstat 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/sysstat direc-
tory 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 us-
ing 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 in-
terprets this value as "N 24 hour periods", ignoring any frac-
tional 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 com-
mand 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, de-
pending on the number of days in a month) in the /var/log/sys-
stat 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/sysstat
directory during the majority of a given day.
REPORTS
Set this variable to false to prevent the sa2 script from gener-
ating reports (the sarDD files).
SA_DIR Directory where the standard system activity daily data and re-
port files are saved. Its default value is /var/log/sysstat.
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 ig-
nored with an already existing one.
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.
FILE
/etc/sysstat/sysstat
AUTHOR
Sebastien Godard (sysstat <at> orange.fr)
SEE ALSO
sadc(8), sa1(8), sa2(8)
https://github.com/sysstat/sysstat
http://pagesperso-orange.fr/sebastien.godard/
Linux JULY 2020 SYSSTAT(5)
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