The purpose of this assignment is to demonstrate how to run jobs on a remote machine. Running jobs remotely is useful when running long, intensive computing scripts. One may want to offload the script or job to a remote machine which is faster and will continue working even after one closes their laptop for the night.
To demonstrate this remote compute capability we start by writing a ‘CPU heavy’ script where we print the date every hour. After we start the script we show it still runs in the background after we logout of the remote machine. We also show that we can run the job without ever logging into the remote machine.
To begin we write a script that will run for an extended period of time.
Using a combination of commands ‘sleep’ and a loop we run the job for a
long time. The command ‘sleep’ tells the script to wait for the amount of
time specified. The value can be in terms of seconds, minutes or hours.
In our script we tell it to sleep for one hour and loop ten times. Each
time we loop we output the date to
stdout using the command ‘date’. This
looping script simulates a script that is ‘CPU intensive’ where we expect
the computation to take hours. Using this script we can test remote
Next we monitor the status of our job in real-time. We want to output our
stdout stream to a file instead of the terminal screen.
Nohup allow us to
stdout steam to a file which we will call
hw05.out. We also
stderror to a file to catch any errors that may occur as our script
runs. Lastly we need to disconnect our processor of running the script
from our current shell otherwise when we log out all child processes of
our shell will also quit. The following command will let us accomplish
all the above concerns.
$ nohup <path/to/script>/hw05.sh > hw05.out 2> hw05.err < /dev/null &
Nohup allow us run a job that won’t be interrupted by hangups. Therefore
when we disconnect our shell and it sends a HUP signal to all child
processes our processes will not terminate. To have our
stdout saved we
output to a file called
hw05.out. The second output argument is the
stderror steam which we can also redirect to a file. All other outputs we
/dev/null which will ensure our script runs successfully.
& at the end of the command allows the script to run in the background.