Visit The New, Modern Unix Linux Community

Nohup with ampersand & process gets disconnected

Thread Tools Search this Thread
Operating Systems Linux Red Hat Nohup with ampersand & process gets disconnected
# 1  
Nohup with ampersand & process gets disconnected

For years I have spawned shell scripts with nohup and ampersand and they run whether or not I stay logged in. Recently a client told us that we had to set a keep alive timeout on all of our Redhat 7.6 Linux servers. Our sysadmin set the following parameters in the sshd_config file on all of our Redhat 7.6 servers:

ClientAliveInterval 900
ClientAliveCountMax 0

Now when I try to nohup an Oracle database clone script or some other type of Oracle database shell script, the script tends to die within 15 minutes. If I run the script through crontab it works fine. I have tried running tests where I use disown after spawning a script with nohup and ampersand, but that doesn't seem to help. Since the scripts are using sqlplus, and that is spawning its own process, my assumption is that the parent process is idle, even though the child process is not idle. Hence, the script dies.

I would use crontab, but then I need to remember to take the job out of crontab, otherwise it will continue to run on the schedule that I used. Does anyone have any suggestions on how to run scripts without them being killed by the OS?

# 2  
If these programs are opening /dev/tty by themselves, nohup can't stop them from getting the boot. Running from crontab they wouldn't, as opening /dev/tty wouldn't get anything anyway.

I'd be really curious what file descriptors you find open in all PID's owned by you after you do a nohup ./script & disown ; exit, visible in /proc/####/fd. If some database client is grabbing /dev/tty maybe it can be convinced not to do so with a commandline switch.

There's also the "at" daemon if you have it, a kind of cron equivalent for one time tasks which lets you specify something to run at a time in the future.

Last edited by Corona688; 04-03-2019 at 06:08 PM..
This User Gave Thanks to Corona688 For This Post:
# 3  
You should consider configuring your ssh terminal client to send keep alives.

The way I read your post is that you are remotely logged into a server using ssh and you are having trouble with your ssh terminal being terminated. You have tried to set up keepalives on the server side (sshd); but you have not configured your client to send keep alives.

I used to have this same problem (very annoying) with my MacOS ssh terminals remotely logged into linux servers. Regardless of my settings on the server side, my ssh terminals would time out, annoyingly. I used to use a work-around like "watch /some/changing/logfile.log" and that would insure the terminal remained alive; but I did not like that bandaid (cluttering up my terminals, since I often have four opened at once on the same screen).

Then, I decided to configure my client terminal to send keepalives to the server (in my case MacOS), and since then my client ssh terminals never die, even when logged in for many days with no terminal activity.

What ssh terminal client are you using?

Or, did I completely misunderstand your question, gandolf989?

When you are talking sshd, linux and keepalives, this leads me to think you are remotely logged in to a linux server and you want to keep the ssh session alive. Isn't that right?
This User Gave Thanks to Neo For This Post:
# 4  
Use screen, just run the script, detach session.

Great tool, written exactly for your use case, and many others.

Hope that helps
This User Gave Thanks to Peasant For This Post:
# 5  
Originally Posted by Peasant
Use screen, just run the script, detach session.

Great tool, written exactly for your use case, and many others.

Hope that helps
Great advice.

I've never used screen and just installed it and will give it a try.

# 6  
I am not sure what your version of nohup is doing.
Try the following script:
# ignore signals HUP INT QUIT
trap "" 1 2 3
# redirect filedescriptors 0...6
exec "$@" </dev/null >/dev/null 2>&1 3>&1 4>&1 5>&1 6>&1

Then run yourscript with
./ yourscript &

--- Post updated at 13:39 ---

BTW screen is also a great collaboration tool. Two and more persons can really share a terminal screen.
This User Gave Thanks to MadeInGermany For This Post:
# 7  
the AT daemon should be a viable option. I just need to look up the syntax.

--- Post updated at 01:22 PM ---

I do use keep alives in my interactive sessions and it works. But this doesn't help when I spawn a process.

--- Post updated at 01:24 PM ---

I like the idea of using screen and I am going to test that. I like that I can go back to a session after the fact and see everything that was there. I just need to figure out how to use it.

--- Post updated at 01:27 PM ---

Cool script. I will have to test it and see how it works. Did you use the Bourne shell for a particular reason?
Why not use the Bash shell? Thanks

Previous Thread | Next Thread
Thread Tools Search this Thread
Search this Thread:
Advanced Search

Test Your Knowledge in Computers #818
Difficulty: Medium
In CSS, E > F matches an F element child of an E element.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Problems with ampersand (&) in sed command

Hello everybody, I have a Problem with sed command. I want to replace a defined string with a string from a database field (dynamic). e.g. sed -i -e 's/%NAME%/'"$HNAME"'/g' The Problem is that the $HNAME variable can contain Special characters like '&' e.g. HNAME="AH Kruger & Co. KG" ... (1 Reply)
Discussion started by: Bambuti2000
1 Replies

2. UNIX for Dummies Questions & Answers

Difference between & and nohup &

Hi All, Can anyone please help me understanding what the difference between the below two? 1. & 2. nohup & (2 Replies)
Discussion started by: Anupam_Halder
2 Replies

3. UNIX for Advanced & Expert Users

Running process in nohup

Hi All, I am facing issue in running a process in nohup. I ran a process in terminal since it is taking too long to complete I need to make it as background and nohup. I tried below and was able to make it in back ground 1. Cntrl + Z 2. bg I am using Korn Shell so disown is not working... (5 Replies)
Discussion started by: arunkumar_mca
5 Replies

4. UNIX and Linux Applications

nohup and & versus functions

when i have a function definition and function call in my script , i am unable to run my script in background with nohup.. Help me out please..... (3 Replies)
Discussion started by: venugopalsmartb
3 Replies

5. Shell Programming and Scripting

Understanding ampersand (&) usage in the command

Please explain the usage of ampersand in the following command who & echo "Total number of users are `who|wc -l`" What I understand is that ampersand is used to run some process in the background. And, what I am expecting from this command is "Output of who should be displayed on the... (2 Replies)
Discussion started by: Shan_u2005
2 Replies

6. UNIX for Dummies Questions & Answers

nohup & mpiexec problems

Hi everyone - I'm trying to start a run of LAMMPS (which takes an input file) with mpiexec on multiple processors. I want to combine this with nohup so that I can log off the node. I've used the syntax below successfully on one cluster, but it doesn't work on the new one I'm using. Any... (0 Replies)
Discussion started by: erin85
0 Replies

7. Shell Programming and Scripting

Execute Script using nohup and &

Hi all, I have one script for which I pass two arguments. In the same script I need to submit this script in background using nohup. My script like this and it is working in HP-UX os but not Solaris. #! /bin/sh if then MTR_PID=$$ export MTR_PID echo " $1 $2... (3 Replies)
Discussion started by: sridhar_423
3 Replies

8. UNIX for Advanced & Expert Users

nohup and background process

What is the difference between running a process using nohup and running a process in background ? Please explain (6 Replies)
Discussion started by: srksn
6 Replies

9. Shell Programming and Scripting

pid of nohup process

I want to print the pid of a nohup process to a file so later I can use the list of pid's in that file to stop the background processes again. I use ksh on AIXv5.3: nohup /start/script.ksh 1>/dev/null 2>&1 print $$ > .pid nohup /start/script2.ksh 1>/dev/null 2>&1 print $$ >> .pid But... (2 Replies)
Discussion started by: rein
2 Replies

10. Shell Programming and Scripting

nohup process hangs

Hi All, I tried searching for this, but I have yet to find anything useful. So here goes, if a script executed from another script with nohup & hangs, does it affect the parent script? Reason I ask, we have a windows box with NFS, and we use it to store some of our files. Currently, I mount the... (2 Replies)
Discussion started by: Sully
2 Replies

Featured Tech Videos