Shell script to enter Docker container and execute command, and eventually exit

Question

I want to write a shell script that enters into a running docker container, edits a specific file and then exits it.

My initial attempt was this -

Create run.sh file.

Paste the following commands into it

docker exec -it container1 bash
sed -i -e 's/false/true/g' /opt/data_dir/gs.xml
exit

Run the script -
```
bash ./run.sh
```

However, once the script enters into the container1 it lands to the bash terminal of it. Seems like the whole script breaks as soon as I enter into the container, leaving parent container behind which contains the script.

When/why do you want to do this? Does your image actually need a custom entry point script that can update config files at startup time based on environment variables or other settings? — David Maze
– David Maze, Commented Jul 18, 2018 at 19:54

Raghuveer Addagada · Accepted Answer · 2018-07-20 14:47:47Z

2

The issue is solved By using the below piece of code

myHostName="$(hostname)"
docker exec -i -e VAR=${myHostName} root_reverse-proxy_1 bash <<'EOF'
sed -i -e "s/ServerName .*/ServerName $VAR/" /etc/httpd/conf.d/vhosts.conf
echo -e "\n Updated /etc/httpd/conf.d/vhosts.conf $VAR \n"
exit

edited Jul 20, 2018 at 14:47

answered Jul 19, 2018 at 9:48

Raghuveer Addagada

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1 Comment

Raghuveer Addagada Over a year ago

here root_reverse-proxy_1 is the name of the docker image

Shiva · Accepted Answer · 2018-07-19 00:01:39Z

1

I think you are close. You can try something like:

docker exec container1 sed -i -e 's/false/true/g' /opt/data_dir/gs.xml

Explanations:

-it is for interactive session, so you don't need it here.
docker can execute any command (like sed). You don't have to run sed via bash

edited Jul 19, 2018 at 0:01

Shiva

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answered Jul 18, 2018 at 14:56

vladmihaisima

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5 Comments

Zia Over a year ago

Thanks, but I got this error : OCI runtime exec failed: exec failed: container_linux.go:348: starting container process caused "exec: \"sed\": executable file not found in $PATH": unknown

vladmihaisima Over a year ago

Is sed installed in the image? Use the full path like "/usr/bin/sed"

Zia Over a year ago

Ahh!! May be that's the issue. Sed is not installed. Unfortunately, I'm pulling the docker image from somewhere else and therefore won't be able to pre-install it, or install it through shell (may be!). But I get the clue.

vladmihaisima Over a year ago

Similar things for easy in place replacement: awk and perl. (maybe one of them is installed...)

Zia Over a year ago

Thanks a lot. Will look into it :)

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