Tools to monitor your Linux systems by command line – part three
In this last article about tools that you can use to monitor a server, we will talk about sysstat. The command sar, which is a tool included in sysstat package, shows a report about the past so you can analyze an incident that was reported a few hours or days ago.
sysstat – Collect, report, or save system activity information (from man sysstat).
Installation (on Ubuntu):
aptitude install sysstat
edit the file /etc/default/sysstat
change the key "enabled" - from 'false' to 'true'
Sometimes a user calls you to report an incident that happened a few hours or days ago. So with iotop, top or htop you can’t see how your server was.
To resolve this issue, you can use sysstat that is a metrics collector and reporter about CPU, memory, disk, swap and others. By default, sysstat saves the indicators each ten minutes into one file every day and writes its contents to a standard output containing information since the computer was started.
You can see about CPU utilization by typing (all processors together):
To see statistics for each individual processor
- sar -P ALL
To see the report of a specific date use -f option:
- sar -f /var/log/sysstat/sa23
with ending time:
- sar -f /var/log/sysstat/sa23 -e 21:00:00
with starting time:
- sar -f /var/log/sysstat/sa23 -s 21:00:00
Report I/O transfer. You can see IOPS (read and write) called tps in sar command
- sar -b
Report activity for each block device (similar to sar -b)
- sar -d
Report activity for network devices (some metrics – number of packets and number of kilobytes per second)
- sar -n DEV
Report activity for network devices (to see statistics errors too – bad packets, errors that happened while transmitting packets, collisions, received and transmitted packets dropped)
- sar -n EDEV
Report queue length and load averages.
- sar -q (number of tasks waiting for run time, load average about last minute, for the past 5 minutes and 10 minutes).
- sar -r
Swap space utilization:
- sar -S (shows the amount of free and used swap)
Report swapping statistics
- sar -W
To see sar in real time, type the command below to watch a live report for each 2 seconds repeated for ten times about the processor.
- sar -u 2 10
More information: man sar or man sysstat