Resource Monitoring Tools

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There are programs available to watch various aspects of your system.



See active internet connections. e.g.

# iftop -i eth1

Will show you websites that don't close a connection, when the tab is left open. A privacy and security nightmare. This is a reason why Javascript is bad.


netstat | head -n 20


ping with the -i flag to set interval to less than 0.1 seconds (unix only and not busybox).
speedtest-cli w/owrt default luci status, real-time graphs, traffic of the lan / wan interface.
ethtool will tell you if your nic supports 1000/m


See RAM usage. Can be watched, to monitor swapping. e.g.

$ vmstat 3

Leave it running. It will update every 3 seconds.


Take htop, and go in the menus. Change the update rate to

0.1 seconds

I think this view is superior to the default. Might slow down machine, so use with discretion, (i.e. don't leave it running).



See HDD accesses. e.g.

# iotop --only
# iotop -o

only flag will show active processes only

# iotop -d 0.01  or -d 0.1

delay flag can be set to be faster than 1 second. Some writes are missed otherwise.

See also: i can't remember how often i test file system speed though. I am not working in a data center. It's never been necessary.

List Open Files

lsof Note: there are different types of lsof (e.g. busybox's)

Filesystem metadata

# dumpe2fs /dev/sda1 | less

Monitor Library Reads from PID

$ ltrace -p -pidhere-

See what a program is doing. (Note: not available on ARM deb repos)

cron monitoring scripts

monitor ip address up/down via ping


LOGFILE=$1_$(date +%A)_LOG

#setup this script in cron each minute, and also
#crontab requires historyfile / lockfile to be blanked (echo "" > file) each day or each hour, whatever you prefer.
#mkdir /var/log/networkalerts
#e.g. $ <ipaddress>
# in /etc/crontab
#*/3 * * * *   root /root/email_alerts/ #tune this frequency based on your priority
#0 */2 * * * root rm /var/log/networkalerts/*LOCKFILE
#0 0 * * *   root rm /var/log/networkalerts/*$(date +%A)*LOG

#keep track of time
  date >> /var/log/networkalerts/$LOGFILE
  ping -c 6 $SERVERIP >> /var/log/networkalerts/$LOGFILE
#nothing after ping, as we need return value
#if return val is error (see man on ping regarding count and deadline)
# == or -eq can be used. == is intuitive, therefore better
  if test $? == 1
#if file empty
#[ -s FILE ] True if FILE exists and has a size greater than zero. Thus, you get "empty.txt" if "diff.txt" is not e>
#    for all the other tests like -s
#   [! -s file] to invert didn't work because of missing spaces (i think)
# must be space between [ and -s and also last bracket. test brackets are unintuitive so don't use them.
#  if [ -s /var/log/networkalerts/$HISTORYFILE ]
  if test -s /var/log/networkalerts/$HISTORYFILE
    exit 5
    # Use your favorite mailer here:
    # explains how to configure email for devuan
    echo "alert" | mutt  -s "Network Down" -- $NOTIFYEMAIL
    #lock file / history file
    echo "alertsent" > /var/log/networkalerts/$HISTORYFILE

hdd full

#usage: feed $1 company name/subject 
df -h | grep 100%
if [ $? -eq 0 ]; then
#send email
  echo "hdd full" | mutt -s $1 alerts@emailaddress 
  echo "do nothing"

cpu temperature

#usage: feed $1 company name/subject 
sensors | grep -e temp -e Core | cut -c 16-19 | sort | grep [[:digit:]] | cut -c 1-2 > /tmp/tmp

while IFS= read -r line
  if [ $line -gt 60 ]; then 
echo $line
echo "overtemperature detected."
done < "$input"

#send email
  echo "cpu temperature overload detected" | mutt -s $1 alerts@email 

fanspeed=$(sensors | grep -e fan1 | cut -c 14-17 | sort | grep [[:digit:]])
  if [ $fanspeed -gt 4000 ]; then 
  echo "fan speed overload detected" | mutt -s $1 alerts@email

monitor hdd usage

#must run as root for access to dmesg

SUBJECT="hdd details"

echo "" > $LOGFILE
echo "" >> $LOGFILE
echo "" >> $LOGFILE
df -h   >> $LOGFILE
echo "" >> $LOGFILE
echo "" >> $LOGFILE
lsblk   >> $LOGFILE
echo "" >> $LOGFILE
echo "" >> $LOGFILE
dmesg | grep -e sda -e sdb -e sdc -e sdd -e sde >> $LOGFILE
echo "" | mutt -s $SUBJECT alerts@email -a $LOGFILE