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sysstat(5) - phpMan

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 compressed. The compression
program is given in the ZIP variable.

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 direc‐
tory, 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 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 mid-night 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 modifica‐
tion 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/sysstat
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).

SA_DIR Directory where the standard system activity daily data and report 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 ignored with an already existing one.

ZIP Program used to compress data and report files.

FILES
/etc/sysstat/sysstat

AUTHOR
Sebastien Godard (sysstat <at> orange.fr)