Alert me by email when a disconnected or unreachable server comes back online 

while ! ping -c1 the_host_down; do sleep 1; done && date | mail -s 'the host is back!' me@example.com

October 10, 2011 — janos

Explanation

  • ping -c1 host sends just one ping and exits with success or error.
  • while will keep running until the ping succeeds
  • When the ping succeeds the while loop will end, and an email will be sent with the date as the message

Limitations

  • Depending on your system the parameter for sending a single ping might be different from -c1
  • Depending on your system the mail command might be different or work differently
network-monitoring email-notification
while sleep date ping mail host