собирать, сообщать или сохранять информацию о деятельности системы (Collect, report, or save system activity information.)
Описание (Description)
The sar command writes to standard output the contents of
selected cumulative activity counters in the operating system.
The accounting system, based on the values in the count and
interval parameters, writes information the specified number of
times spaced at the specified intervals in seconds. If the
interval parameter is set to zero, the sar command displays the
average statistics for the time since the system was started. If
the interval parameter is specified without the count parameter,
then reports are generated continuously. The collected data can
also be saved in the file specified by the -o filename flag, in
addition to being displayed onto the screen. If filename is
omitted, sar uses the standard system activity daily data file
(see below). By default all the data available from the kernel
are saved in the data file.
The sar command extracts and writes to standard output records
previously saved in a file. This file can be either the one
specified by the -f flag or, by default, the standard system
activity daily data file. It is also possible to enter -1, -2
etc. as an argument to sar to display data of that days ago. For
example, -1 will point at the standard system activity file of
yesterday.
Standard system activity daily data files are named saDD or
saYYYYMMDD, where YYYY stands for the current year, MM for the
current month and DD for the current day. They are the default
files used by sar only when no filename has been explicitly
specified. When used to write data to files (with its option
-o), sar will use saYYYYMMDD if option -D has also been
specified, else it will use saDD. When used to display the
records previously saved in a file, sar will look for the most
recent of saDD and saYYYYMMDD, and use it.
Standard system activity daily data files are located in the
/var/log/sa directory by default. Yet it is possible to specify
an alternate location for them: If a directory (instead of a
plain file) is used with options -f or -o then it will be
considered as the directory containing the data files.
Without the -P flag, the sar command reports system-wide (global
among all processors) statistics, which are calculated as
averages for values expressed as percentages, and as sums
otherwise. If the -P flag is given, the sar command reports
activity which relates to the specified processor or processors.
If -P ALL is given, the sar command reports statistics for each
individual processor and global statistics among all processors.
Offline processors are not displayed.
You can select information about specific system activities using
flags. Not specifying any flags selects only CPU activity.
Specifying the -A flag selects all possible activities.
The default version of the sar command (CPU utilization report)
might be one of the first facilities the user runs to begin
system activity investigation, because it monitors major system
resources. If CPU utilization is near 100 percent (user + nice +
system), the workload sampled is CPU-bound.
If multiple samples and multiple reports are desired, it is
convenient to specify an output file for the sar command. Run the
sar command as a background process. The syntax for this is:
sar -o datafile interval count >/dev/null 2>&1 &
All data are captured in binary form and saved to a file
(datafile). The data can then be selectively displayed with the
sar command using the -f option. Set the interval and count
parameters to select count records at interval second intervals.
If the count parameter is not set, all the records saved in the
file will be selected. Collection of data in this manner is
useful to characterize system usage over a period of time and
determine peak usage hours.
Note: The sar command only reports on local activities.
