Linux

vmstat

vmstat
vmstat -S M # show in MB
free -m ; sync # show free mem and write current
sudo bash -c "echo 3 > /proc/sys/vm/drop_caches" # clean cache
free -m # show memory
vmstat 5 3 # run 3 times every 5 sec

list vm stats. memory, disk, etc

who

who
who -l # who is logged in and process
who -T # is messaging turned on
mesg # send message to user

netstat

netstat -alt # list tcp/udp active ports
netstat -alx # list all tcp/udp/sockets
netstat -i # list interfaces
netstat -s #

top

top

ps

ps # list process
ps all # list all process

pstree

pstree #show systemd tree

lsof

lsof -i # list network

iptables

sudo iptables -nvL # show data in/out

watch

watch -d sudo iptables -nvL # show every 2 sec and highlight changes

systat

apt-get install sysstat
sudo vi /etc/default/sysstat # turn it on with boolean
cat /etc/cron.d/sysstat # list cron jobs

sar # command to review sysstat
sar -q 1 3 # display load avg 3 times 1 sec int
sar -q -f /var/log/sysstat/sa15 # ubuntu read day 15

sar -w # context switch per sec
sar -n DEv # network interface stats
sar -b # overall activity
sar -q -s 10:00:00 -e 11:00:00 # between times for today