sysstat(5) - man - phpMan

Che Dong

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.

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 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", ig‐
noring 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 modification time up a
bit), the sa2 script will leave 30 files untouched. So for a setting of 28, and count‐
ing 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/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).

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 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/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 ex‐
ample 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)