Any idea why when I connect remotely (ssh session) to my Google Compute Engine instance, if I run a command (run an HTTP API) and leave, this one stops running as well?
./main PORT // Stops when I leave
./main PORT & // Stops when I leave as well..
No matter what, if I disconnect from my current ssh session, my API stops, even if the engine still seems to run fine
When you disconnect your terminal, all processes started by that terminal are sent a "hangup" signal which, by default, causes the process to terminate. You can trap the hangup signal when you launch a process at cause the signal to be silently ignored. The easiest way to achieve this is with the nohup command. For example:
nohup ./main PORT &
References:
What Is Nohup and How Do You Use It?
Unix Nohup: Run a Command or Shell-Script Even after You Logout
nohup(1) - Linux man page
Related
My ansible playbook consist several task in it and I am running my ansible playbook on Virtual Machine. I am using ssh method to log in to VM and run the playbook. if my ssh window gets closed during the execution of any task (when internet connection is not stable and not reliable), the execution of ansible playbook stops as the ssh window already got closed.
It takes around 1 hour for My play book to run, and sometimes even if I loose internet connectivity for few seconds , the ssh terminal lost its connection and thus entire playbook stops. any idea how to make ansible script more redundant to avoid this problem ?
Thanks in advance !!
If you need to run a job on an external system that hangs for a long time and it is relevant that the task completes. It is extremly bad idea to run that job in the foreground.
It is not important that the task is Ansible or the connection is SSH. In every case you would always just "push" the command to the remote host and send it to background with something like "nohup" if available. The problem is of course the tree of processes. Your connection creates a process on the remote system and that creates the job you want to run. Is the connection gets lost, al subprocesses will be killed automatically by the OS.
So - under Windows - maybe use RDP to open a screen that stays available even after connection is lost or use something like Cygwin and nohup via SSH to change the hung up your process from the ssh session.
Or - when you need to run a playbook on that system install for example a AWX container and use that. There are many options based on your requirements, resources and administrative options.
I have an application written in python, which run on a VPS server. It is a small application that writes, reads and receives read requests from a SQLite database, through a TCP socket.
The downside is that the application runs only when the console is open (using the ssh protocol), when closing the console, that is, the ssh session closes the application.
How should it be implemented? Or I must implement it? because the server is a ubuntu server
nohup should help in your case:
in your ssh session, launch your python app prefixed with nohup, as recommended here
exit your ssh session
The program should continue working even if its parent shell (the ssh session) is terminated.
There are (at least) two solutions:
1- The 'nohup' command, use it as follows: nohup python3 yourappname.py &
This will run your program in the background and won't be killed if you terminate the ssh session, It'll also give you a free prompt after running this command to continue your work.
2- Another GREAT option is the 'screen' command.
This gives you everything that nohup gives you, besides It allows you to check the output of your program (if any) in later logins. Although It may look a little complicated at first sight, but it's SUPER COOL! and I highly recommend you to learn it and enjoy it for the rest of your life!
A good explanation of it is available here
A compute instance I had running stopped working and I am no longer able to ssh to it from the browser. When I try it hangs forever and eventually I get the error message:
You cannot connect to the VM instance because of an unexpected error.
Wait a few moments and then try again. (#13)
I looked here for common issues. I made a snapshot and tried recreating with a larger disk, in a different region and with a bigger compute instance but I was still unable to connect. When other users try to connect they have the same problem. I'm using a standard container so I expect the google daemon should be running.
This instance was collecting tweets and writing output to GCS regularly. Since ssh stopped working the instance has also stopped writing output.
Does anyone have any idea what could have gone wrong?
I would also suggest checking the Serial Console of the machine to see if there are any messages which provide any clues. For example, if the boot disk has run out of space (which can prevent SSH connectivity), there will be some messages displayed in the Serial Console implying this.
You could also try connecting to the machine via the Serial Console to troubleshoot the issue by following the advice here.
When you try to SSH into the instance from the Cloud Shell for example, using the following command, the output should provide some clues as to why you cannot SSH into the machine:
$ gcloud compute ssh INSTANCE_NAME --zone ZONE
If you are on a VPC network, try to check the applicable network TAG that allows the instance to use SSH and provide that tag to your instance. Because it could be the Firewall rules that are blocking your instance from creating the ssh connection.
I've got a VMware ESXi server that I connected to via SSH to run a process. (I was running "vmkfstools --punchzero myVirtualDrive.vmdk" to reclaim space on a virtual disk). The SSH client connection was disconnected when the process was only 70% complete (with several hours of estimated time remaining).
Was the process terminated when the SSH client dropped its connection to the ESXi host?
Is there any way to tell if the process is still running?
I did a quick ps|grep to find it, but didn't see anything that looked like vmkfstools.
On most standard linux machines, I use "screen" to avoid SSH client disconnection issues, but since the ESXi shell is purposely a very stripped down environment, I just ran the command straight away.
Thoughts?
The command was killed when you disconnected.
What you can do to prevent this in the future is to run the command with nohup. This will run your command in the background, continuing even when your shell "hangs up".
What I usually do when I expect a command to run long:
I ssh to a Linux machine that runs 24/7
start screen
ssh to the ESXi host
start the command
This way I don't have to worry about disconnects, I can just detach screen and go home after work and reattach screen the next morning to check the status of the command.
This was exactly what I was looking for, thanks all. I attempted to unmap unused block on LUNs which is vmfs 5 file system. I run this cmd esxcli storage vmfs unmap -l [LUN-NAME] I wonder that what will happen if I close remote SSH connection while this cmd process still running.
I am running a process that takes long time to finish on a remote server. The process gets killed when my ssh connection to the remote machine is dropped. Is there a way I can continue running the process even after my ssh connection drops?
There is another similar question.
The answer provided there was to use the POSIX command nohup to ignore the ssh termination and allow the process to continue running.