I'm creating a simple Traffic simulator: a client that curl a Webserver every 10 seconds. The client(Debian) and the WebServer are configured using Ansible. The background-cycle is closed when the Ansible-SSH connection is closed.
At first I launched the command:
$ while true; do curl python_webserver:8000; sleep10; done </dev/null >/dev/null 2>&1 &;
$ disown
And It works fine from Bash, but if I put it into a script, it exit at ssh-connection end.
I try some other solutions, like using:
$ nohup [command]
$ nohup /bin/bash -c '[command]
or using "deamonize" but nothing worked. Nothing I found online works; maybe I'm missing something important. (Writing the pid is important, but not fundamental)
I here the script, maybe there is a big newbie error.
#!/bin/bash
PORT=8000
while true; do
curl python_webserver:$PORT
sleep 10
done >/dev/null 2>&1 &
ANSIBLE_CLIENT_PID=$!
echo $ANSIBLE_CLIENT_PID >> /tmp/ANSIBLE_PID.txt
disown
The answers is
nohup sh -c 'while true; do curl python_webserver:'"$PORT"'; sleep 10; done >/dev/null 2>&1' &
Probably I made a mistake with quotation marks.
Thank you all for you help
(especially Kamil Cuk for the solution)
Related
I want to have one script which starts a services in another server.
I have tested that the script works as expected in the server where the server is going to run.
This is the code which starts the service and monitors the log until it is in the startup process:
pkill -f "$1"
nohup java -jar -Dspring.profiles.active=$PROFILE $1 &
tail -n 0 -f nohup.out | while read LOGLINE
do
echo $LOGLINE
[[ "${LOGLINE}" == *"$L_LOG_STRING"* ]] && pkill -P $$ tail
done
This works fine as long as I execute that from that machine.
Now I want to call that script from another server:
#!/usr/bin/env bash
DESTINATION_SERVER=$1
ssh root#$DESTINATION_SERVER /bin/bash << EOF
echo "Restarting first service..."
/usr/local/starter.sh -s parameter
echo "Restarting second service..."
/usr/local/starter.sh -s parameter2
EOF
Well, everytime I try that the script of the remote server gets stuck in the "while READ" loop. But as I said, when I execute it locally from the server works fine, and in my "not simplified script" I´m not using any system variable or similar.
Update: I just tried to simplify the code even more with the following lines in the first scenario:
pkill -f "$1"
nohup java -jar -Dspring.profiles.active=$PROFILE $1 &
tail -n 0 -f nohup.out | sed "/$L_LOG_STRING/ q"
I'd say the problem is some how in the "|" through ssh, but I still can find why.
it seems that the problem comes from not having an interactive console when you execute the ssh command, therefore the nohup command behaves strangly.
I could solve it in two ways, outputing the code to the file explicitly:
"nohup java -jar -Dspring.profiles.active=test &1 >> nohup.out &"
instead of:
"nohup java -jar -Dspring.profiles.active=test &1&"
Or changing the way I access via ssh adding the tt option (just one did not work):
ssh -tt root#$DESTINATION_SERVER /bin/bash << EOF
But this last solution could lead to other problems with some character, so unless someone suggests another solution that is my patch which makes it work.
I'm trying to run a script that is required to have an exit code of 0. Unfortunalty I cannot use an init.d or other startup script to control this this, so I must make this work.
Basically if I understand AWS's docs correctly (elastic beanstalk), I need be able to run the following two commands and exit with a 0 and provide no other output to stdout.
As the root user I need to cd to a particular dir and run these two commands:
pkill -f que
bundle exec que
In my actually script I have:
#!/usr/bin/env bash
su -s /bin/bash -c "cd /some/dir && nohup pkill -f que &>/dev/null &"
sleep 10
su -s /bin/bash -c "cd /some/dir && nohup bundle exec que &"
Which still causes this error to be raised:
returned non-zero exit status 1 (Executor::NonZeroExitStatus)
Any tips for how to silently run those commands correctly?
I'm also looking at these for ideas:
https://blog.eq8.eu/article/aws-elasticbeanstalk-hooks.html
http://www.dannemanne.com/posts/post-deployment_script_on_elastic_beanstalk_restart_delayed_job
But its still not clear to me how this is supposed to exit successfully
Perhaps I'm missing something, but wouldn't this be easily solved by using two shell scripts? One with cd, pkill, and bundle. Call this script (foo.sh) something like:
#!/usr/bin/env bash
su -c ./foo.sh > /dev/null 2>&1 < /dev/null
exit 0
I am executing one shell script from another shell script. The included shell script is not terminating after execution. But when I run it separately, it works fine and terminates normally.
Script 1
#! /bin/bash
WebApp="R"
#----------Check for Web Application Status
localWebAppURL="http://localhost:8082/"
if curl --max-time 5 --output /dev/null --silent --head --fail "$localWebAppURL"; then
WebApp="G"
else
exec ./DownTimeCalc.sh &
fi
echo "WebApp Status|\"WebApp\":\"$WebApp\""
In above script I am calling another script called DownTimeCalc.sh.
DownTimeCalc.sh
#! /bin/bash
WebApp="R"
max=15
for (( i=1; i <= $max; ++i ))
do
if curl --max-time 5 --output /dev/null --silent --head --fail "http://localhost:8082/"; then
WebApp="G"
echo "Status|\"WebApp\":\"$WebApp\""
break
else
WebApp="R"
sleep 10
fi
echo "Status|\"WebApp\":\"$WebApp\""
done
echo "finished"
exit
exec ./DownTimeCalc.sh &
You don't need exec. If you want to run the script and wait for it to complete then just write:
./DownTimeCalc.sh
Or if you want to run it in the background and have the first script continue, write:
./DownTimeCalc.sh &
When you use & the launched process will be launched in the background and will run in the background while other commands from the foreground script run or you interact with the shell. It's doing what you told it. If you press Enter you will see any queued-up stderr output, and if you type fg it will bring the process to the foreground if it is still running.
You probably don't want to use & in this case, though.
I have a script that uses ssh to login to a remote machine, cd to a particular directory, and then start a daemon. The original script looks like this:
ssh server "cd /tmp/path ; nohup java server 0</dev/null 1>server_stdout 2>server_stderr &"
This script appears to work fine. However, it is not robust to the case when the user enters the wrong path so the cd fails. Because of the ;, this command will try to run the nohup command even if the cd fails.
The obvious fix doesn't work:
ssh server "cd /tmp/path && nohup java server 0</dev/null 1>server_stdout 2>server_stderr &"
that is, the SSH command does not return until the server is stopped. Putting nohup in front of the cd instead of in front of the java didn't work.
Can anyone help me fix this? Can you explain why this solution doesn't work? Thanks!
Edit: cbuckley suggests using sh -c, from which I derived:
ssh server "nohup sh -c 'cd /tmp/path && java server 0</dev/null 1>master_stdout 2>master_stderr' 2>/dev/null 1>/dev/null &"
However, now the exit code is always 0 when the cd fails; whereas if I do ssh server cd /failed/path then I get a real exit code. Suggestions?
See Bash's Operator Precedence.
The & is being attached to the whole statement because it has a higher precedence than &&. You don't need ssh to verify this. Just run this in your shell:
$ sleep 100 && echo yay &
[1] 19934
If the & were only attached to the echo yay, then your shell would sleep for 100 seconds and then report the background job. However, the entire sleep 100 && echo yay is backgrounded and you're given the job notification immediately. Running jobs will show it hanging out:
$ sleep 100 && echo yay &
[1] 20124
$ jobs
[1]+ Running sleep 100 && echo yay &
You can use parenthesis to create a subshell around echo yay &, giving you what you'd expect:
sleep 100 && ( echo yay & )
This would be similar to using bash -c to run echo yay &:
sleep 100 && bash -c "echo yay &"
Tossing these into an ssh, and we get:
# using parenthesis...
$ ssh localhost "cd / && (nohup sleep 100 >/dev/null </dev/null &)"
$ ps -ef | grep sleep
me 20136 1 0 16:48 ? 00:00:00 sleep 100
# and using `bash -c`
$ ssh localhost "cd / && bash -c 'nohup sleep 100 >/dev/null </dev/null &'"
$ ps -ef | grep sleep
me 20145 1 0 16:48 ? 00:00:00 sleep 100
Applying this to your command, and we get
ssh server "cd /tmp/path && (nohup java server 0</dev/null 1>server_stdout 2>server_stderr &)"
or:
ssh server "cd /tmp/path && bash -c 'nohup java server 0</dev/null 1>server_stdout 2>server_stderr &'"
Also, with regard to your comment on the post,
Right, sh -c always returns 0. E.g., sh -c exit 1 has error code
0"
this is incorrect. Directly from the manpage:
Bash's exit status is the exit status of the last command executed in
the script. If no commands are executed, the exit status is 0.
Indeed:
$ bash -c "true ; exit 1"
$ echo $?
1
$ bash -c "false ; exit 22"
$ echo $?
22
ssh server "test -d /tmp/path" && ssh server "nohup ... &"
Answer roundup:
Bad: Using sh -c to wrap the entire nohup command doesn't work for my purposes because it doesn't return error codes. (#cbuckley)
Okay: ssh <server> <cmd1> && ssh <server> <cmd2> works but is much slower (#joachim-nilsson)
Good: Create a shell script on <server> that runs the commands in succession and returns the correct error code.
The last is what I ended up using. I'd still be interested in learning why the original use-case doesn't work, if someone who understands shell internals can explain it to me!
After trying to figure out why a Capistrano task (which tried to start a daemon in the background) was hanging, I discovered that using && in bash over ssh prevents a subsequent program from running in the background. I tried it on bash 4.1.5 and 4.2.20.
The following will hang (i.e. wait for sleep to finish) in bash:
ssh localhost "cd /tmp && nohup sleep 10 >/dev/null 2>&1 &"
The following won't:
ssh localhost "cd /tmp ; nohup sleep 10 >/dev/null 2>&1 &"
Neither will this:
cd /tmp && nohup sleep 10 >/dev/null 2>&1 &
Both zsh and dash will execute it in the background in all cases, regardless of && and ssh. Is this normal/expected behavior for bash, or a bug?
One easy solution is to use:
ssh localhost "(cd /tmp && nohup sleep 10) >/dev/null 2>&1 &"
(this also works if you use braces, see second example below).
I did not experiment further but I am reasonably convinced it has to do with open file descriptors hanging around. Perhaps zsh and dash bind the && so that this means what has to be spelled as:
{ cd /tmp && nohup sleep 10; } >/dev/null 2>&1
in bash.Nope, quick experiment in dash shows that echo foo && echo bar >file only redirects the latter. Still, it has to have something to do with lingering open fd's causing ssh to wait for more output; I've run into this a lot in the past.
One more trick, not needed if you use the parentheses or braces for this particular case but might be useful in a more general context, where the set of commands to do with && are more complex. Since bash seems to be hanging on to the file descriptor inappropriately with && but not with ;, you can turn a && b && c into a || exit 1; b || exit 1; c. This works with the test case:
ssh localhost "true || exit 1; echo going on; nohup sleep 10 >/dev/null 2>&1 &"
Replace true with false and the echo of "going on" is omitted.
(You can also set -e, although sometimes that is a bigger hammer than desired.)
This seems to work:
ssh localhost "(exec 0>&- ; exec 1>&-; exec 2>&-; cd /tmp; sleep 20&)"