I am running some simulations on another machine via ssh. Here is what I do
ssh username#ipp.ip.ip.ip
Go to the right directory
cd path/to/folder
And then I just call my executable
.\myexecutable.exe
The issue is that every time the ssh disconnect, the simulations stops. How can I make sure the simulations doesn't stop on the other machine? Will I somehow receive potential error messages (assuming the code will crash) once I reconnect (ssh)?
You should launch a screen or tmux to create a terminal from which you can detach, leave running in the background and later reattach.
Further reading:
http://ss64.com/osx/screen.html
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/screen.1.html
You may also want to try out Byobu:
http://byobu.co
run your command as follows : nohup ./myexecutable.exe >nohup.out 2>&1 &
The & is to run the command in the background
The >nohup.out 2>&1 sends your stdout and stderr to nohup.out)
Note the '/' as opposed to '\' - which won't work on osx
Related
I have a VM that I want running indefinitely. The server is always running but I want the script to keep running after I log out. How would I go about doing so? Creating a cron job?
In general the following steps are sufficient to convince most Unix shells that the process you're launching should not depend on the continued existence of the shell:
run the command under nohup
run the command in the background
redirect all file descriptors that normally point to the terminal to other locations
So, if you want to run command-name, you should do it like so:
nohup command-name >/dev/null 2>/dev/null </dev/null &
This tells the process that will execute command-name to send all stdout and stderr to nowhere (instead of to your terminal) and also to read stdin from nowhere (instead of from your terminal). Of course if you actually have locations to write to/read from, you can certainly use those instead -- anything except the terminal is fine:
nohup command-name >outputFile 2>errorFile <inputFile &
See also the answer in Petur's comment, which discusses this issue a fair bit.
So, I have a long running script (of order few days) say execute.sh which I am planning to execute on a server on which I have a user account...
Now, I want to execute this script so that it runs forever even if I logoff or disconnect from the server??
How do i do that?
THanks
You have a couple of choices. The most basic would be to use nohup:
nohup ./execute.sh
nohup executes the command as a child process and detaches from terminal and continues running if it receives SIGHUP. This signal means sig hangup and will getting triggered if you close a terminal and a process is still attached to it.
The output of the process will getting redirected to a file, per default nohup.out located in the current directory.
You may also use bash's disown functionality. You can start a script in bash:
./execute.sh
Then press Ctrl+z and then enter:
disown
The process will now run in background, detached from the terminal. If you care about the scripts output you may redirect output to a logfile:
./execute.sh > execute.log 2>&1
Another option would be to install screen on the remote machine, run the command in a screen session and detach from it. You'll find a lot of tutorials about this.
nohup (no hangup) it and run it in the background:
nohup execute.sh &
Output that normally would have gone to the screen (STDOUT) will go to a file called nohup.out.
I am trying to execute a remote command for one of my scripts. I have to run this script across many servers. so i will put it in a script. What I am trying to do is
ssh root#10.158.42.12 nohup perl /script/myscript.pl 06/04/2014 60 &
The script runs just fine but there is an info message which is displayed whenever you try to login . The one many of you would be familiar with ..
|-----------------------------------------------------------------|
| This system is for the use of authorized users only. |
| Individuals using this computer system without authority, or in |
Due to this the script execution is haulted unless an enter is pressed. I want to put the script in a cronjob for automatic execution, so i dont need to see this info message.
Here's my theory:
Your command doesn't run the program in the background on the server. It runs runs the program in the foreground on the server, and then you background ssh.
Since ssh runs in the background, you are immediately returned to your prompt.
Milliseconds later, ssh overwrites your prompt with this message and runs the command.
You are now looking at the ssh message and no prompt.
You hit press enter, which causes the prompt to be redrawn on the next line.
This leads you to believe ssh was actually waiting for you to press enter. In reality, the command was already run, and bash was ready for new commands, just obscured by ssh noise.
How to test:
If I'm right, pressing Ctrl+L instead of Enter will clear the screen and show the bash prompt. (assuming you don't use bash's vi mode).
If I'm not, Ctrl+L will instead either do nothing, print the ssh message again or just write ^L to the screen.
How to fix if I'm right:
ssh -f root#10.158.42.12 'nohup perl /script/myscript.pl 06/04/2014 60 &' 2> /dev/null
I logged in to a remote server via ssh and started a php script. Appereantly, it will take 17 hours to complete, is there a way to break the connection but the keep the script executing? I didn't make any output redirection, so I am seeing all the output.
Can you stop the process right now? If so, launch screen, start the process and detach screen using ctrl-a then ctrl-d. Use screen -r to retrieve the session later.
This should be available in most distros, failing that, a package will definitely be available for you.
ctrl + z
will pause it. Than type
bg
to send it to background. Write down the PID of the process for later usage ;)
EDIT: I forgot, you have to execute
disown -$PID
where $PID is the pid of your process
after that, and the process will not be killed after you close the terminal.
you described it's important to protect script continuation. Unfortunately I don't know, you make any interaction with script and script is made by you.
continuation protects 'screen' command. your connection will break, but screen protect pseudo terminal, you can reconnect to this later, see man.
if you don't need operators interaction with script, you simply can put script to background at the start, and log complete output into log file. Simply use command:
nohup /where/is/your.script.php >output.log 2&>1 &
>output.log will redirect output into log file, 2&>1 will append error stream into output, effectively into log file. last & will put command into background. Notice, nohup command will detach process from terminal group.
At now you can safely exit from ssh shell. Because your script is out of terminal group, then it won't be killed. It will be rejoined from your shell process, into system INIT process. It is unix like system behavior. Complete output you can monitor using command
tail -f output.log #allways breakable by ^C, it is only watching
Using this method you do not need use ^Z , bg etc shell tricks for putting command to the background.
Notice, using redirection to nohup command is preferred. Otherwise nohup will auto redirect all outputs for you to nohup.out file in the current directory.
You can use screen.
I ssh to another server and run a shell script like this nohup ./script.sh 1>/dev/null 2>&1 &
Then type exit to exit from the server. However it just hangs. The server is Solaris.
How can I exit properly without hanging??
Thanks.
I assume that this script is a long running one. In this case you need to detach the process from the terminal that you wish to close when you terminate your ssh session.
Actually you already done most of the work by reassigning both stdout and stderr to /dev/null, however you didn't do that for stdin.
I used the test case of:
ssh localhost
nohup sleep 10m &> /dev/null &
^D
# hangs
While
ssh localhost
nohup sleep 10m &> /dev/null < /dev/null &
^D
# exits
I second the recommendation to use the excellent gnu screen, that will do this service for you, among others.
Oh, and have you considered running the script directly and not within a shell? I.e.:
ssh user#host script.sh
If you're trying to leave a command running remotely after you close your SSH link, I strongly recommend you use screen and learn to detach the screen. That's much better than leaving background processes around; it also lets you reconnect and see what the process is up to.
Since you haven't provided us with script.sh, I don't think we can know for sure why the command is hanging.
You can use the command :
~.
This command close the ssh session.
sh -c ./script.sh &