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Tools

Network​

iptraf

I/O​

iostat
sar
vmstat

Memory​

free
pmap

Process and Load​

pstree
mpstat # multiprocessor statistics
numastat
strace # process system calls

We can create stress on system by running:

stress

# 8 cpu-intensive processes
# 4 I/O intensive processes 
# 6 memory-intensive processes 
# allocating 256 MB by default.  
# The size can bechanged as in--vm-bytes 128M.•  
# Run the stress test for 20 seconds.

stress-ng -c 8 -i 4 -m 6 -t 20s

Logs​

System logs located in /var/log.

rsyslogd and journalctl are used to interact with system logs.

To view system logs:


tail -f /var/log/messages
tail -f /var/log/syslog

# OR
dmesg -w

Important logs:

  • boot.log - system boot messages
  • dmesg - kernel messages after boot
  • messages.log/syslog.log - all important system messages.
  • secure - security related messages.

Files are rotated using logrotate (configuration in /etc/logrotate.conf.

Systems Activity Report (sar)​

Backend of sar is System Activity Data Collector (sadc). sadc collects and accumulates info and stores it in /var/log/sa.


sudo sar [options] [interval] [count]

# CPU information, every 3 seconds for 3 times
sudo sar 3 3 

# All information every 2 seconds
sudo sar -A 2

All commands can be found here

We can use the ksar to generate graphs from sar data.

Process Monitoring​

  • ps

    ps auxf # will show ancestry
    ps -elf
    ps -eL
    ps -C "bash"

    # Choose columns
    ps -o pid,cputime,command

    Commands which are in [] are threads. and exist only within the kernel.

    VSZ - process virtual size in KB

    RSS - resident set size. Non-swapped memory a task is using in KB.

    STAT - State of the process.

  • pstree

    pstree -aAp 2408