I have a fairly easy Dockerfile for a Go app:
FROM golang:onbuild
EXPOSE 5000 5001
Now when I run it (not when building the image!) I would like to change a value in a html file which gets statically served, possibly using sed to use an environment variable previously specified with -e to docker run. How can I do that?
You can try something like this:
FROM golang:onbuild
COPY ./docker-entrypoint.sh /
EXPOSE 5000 5001
ENTRYPOINT ["/docker-entrypoint.sh"]
Note: you need to copy entry point file with your sed script somewhere into container (done on line 2)
and docker-entrypoint.sh with your sed script
# execute sed only **if variable exists**
sed -ri "s/<title>.*/<title>$ENVIRONMENT_VARIABLE</title>/" /path_to_html_file/index.html
- simple example of replacement line with new title (passed in run as env. variable) in index.html file
Note: just keep in mind to run sed only if environment variable was served as #STLMikey shows.
and run docker container with $ENVIRONMENT_VARIABLE
eg:
docker run -d -t -i -e ENVIRONMENT_VARIABLE='New website title' --name=container_name IMAGE_NAME
One option is to use the --entrypoint option during docker run:
docker run --entrypoint /some/sh/script.sh <imagename>
where script.sh is a file inside your container, and contains something like:
#!/bin/env bash
if [[ "$myenvvar" == 'myvalue' ]]; then
# sed your file here
else
#don't do that
fi
If you dont like the idea of overriding the entrypoint at run time, you might consider using the CMD or ENTRYPOINT options in your Dockerfile.
Related
I am a docker beginner. I have used this SO post to run a shell script with docker run and this works fine. However, what I am trying to do is to apply my shell script to a file that lives in my current working directory, where Dockerfile and script are.
My shell script - given a file as an argument, return its name and the number of lines:
#!/bin/bash
echo $1
wc -l $1
Dockerfile:
FROM ubuntu
COPY ./file.sh /
CMD /bin/bash file.sh
then build and run:
docker build -t test .
docker run -ti test /file.sh text_file
This is what I get:
text_file
wc: text_file: No such file or directory
I'm left clueless why the second line doesn't work, why the file can't be found. I don't want to copy my text_file to the container. Ideally, I'd like to run my script from docker container on any file in my current working directory.
Any help will be much appreciated.
Thanks!!
You're building your Docker image containing the script /file.sh. Still, your Docker container does not contain (or know) about the file text_file which you're passing as an argument.
In order to make it known to your Docker container, you have to mount it when running the container.
docker run --rm -it -v "$PWD"/text_file:/text_file test /file.sh /text_file
In order to check for other files, you just have to swap text_file in both the mount and the argument.
Notes
In addition to Docker volume mounts, I might suggest some more improvements to spice up your image.
In order to run a script, you don't have to use ubuntu as your base image. You might be fine with alpine or even more focused bash. And don't forget to use tags in order to enforce the exact same behavior over time.
You can set your script as an ENTRYPOINT of your Dockerfile. Then, your only specifying the script name (text_file in that case) as your command.
When mounting files, you can change the name of the file in your container. Therefore, you can simplify your script and just mounting the file to test at the exact same place every time you run the container.
FROM alpine:3.10
WORKDIR /tmp
COPY file.sh /usr/local/bin/wordcount
ENTRYPOINT /usr/local/bin/wordcount
CMD file
Then,
docker run --rm -it -v "PWD"/text_file:/tmp/file test
will do the job.
I have a bash script running inside a docker container. In this script, I set the value of some variable.
Can I somehow access the value of this variable outside the container?
I tried to make the variable "global" but could not figure out how to do it. Is it a good idea to make the required variable an environment variable inside the container?
How to reproduce
Create a bash script called temp.sh with the following contents:
a=$RANDOM
Now, run this file in a docker container as follows:
docker run -it --rm -v $(pwd):/opt alpine sh -c "sh /opt/temp.sh"
Desired behaviour: To be able to access the variable a outside the docker container
Credit: This comment by Mark
I mounted a directory on the docker filesystem using
docker run -v <host-file-system-directory>:<docker-file-system-directory>
In the bash script, I added
echo "$variable" >docker-file-system-directory/variable.txt
As I had mounted a host filesystem directory on the docker filesystem, I can still access variable.txt simply using cat <host-file-system-directory>/variable.txt
Note that docker-file-system-directory must be an absolute path, and not a relative path.
One way of achieving that is using docker exec, if your container is running and has access to bash.
#!/usr/bin/env bash
set -x
yourContainerName="testContainerName"
test=$(docker exec -i "${yourContainerName}" bash <<EOF
# do some work here e.g. execute your script
testVar="thisIsTest" # the value we want to access outside of container
echo \$testVar
EOF
)
echo $test
We pass a multiline script to docker container, which in the end echo's the value we need. This value is then accessible from shell that executed docker exec.
Output looks like this:
++ docker exec -i testContainerName bash
+ test=thisIsTest
+ echo thisIsTest
thisIsTest
I have a simple Dockerfile that copies over a template which I used sed to replace some of the variables. Pretty straight forward. Looks very doable and from what I've seen/read for all intents and purposes, it should do it.
COPY /my-dir/my-textfile.conf /to/my/docker/path.conf
RUN sed -i s:TEXTTOREPLACE:my-new-text:g /to/my/docker/path.conf
I then run docker build.... then docker run ... bash
then I cat my file and TEXTTOREPLACE is still there.
Run the same sed command in the bash and it works no problem.
Any thoughts? What am I doing wrong/not seeing?
Thanks!
EDIT per request: base image is debian:7.11, work station is MAC OSX
Just to recap.
I have the file my-textfile.conf in my working directory. Its content is:
I need to change TEXTTOREPLACE with my-new-text
My test system is Ubuntu Linux 16.04 running Docker version 18.09.0, build
4d60db4.
This is the Dockerfile
FROM debian:7.11
COPY my-textfile.conf /tmp/path.conf
RUN sed -i s:TEXTTOREPLACE:my-new-text:g /tmp/path.conf
I run the following commands:
docker build -t mytestimage .
docker run -ti -d --name mytestcontainer mytestimage
docker exec -ti mytestcontainer /bin/bash
Then, inside the container, I run:
cat /tmp/path.conf
and I get this result:
I need to change my-new-text with my-new-text
So it seems it works as expected.
I have the following piece of definition in a Dockerfile:
# This aims to be the default value if -e is not present on the run command
ENV HOST_IP=127.0.0.1
...
COPY /container-files/etc/php.d/zz-php.ini /etc/php5/mods-available/zz-php.ini
RUN ln -s /etc/php5/mods-available/zz-php.ini /etc/php5/apache2/conf.d/zz-php.ini
COPY /container-files/init-scripts/setup_xdebug_ip.sh /usr/local/bin/setup_xdebug_ip.sh
RUN chmod +x /usr/local/bin/setup_xdebug_ip.sh
CMD ["/usr/local/bin/setup_xdebug_ip.sh", "/usr/local/bin/setup_php_settings.sh"]
This is the relevant piece of definition at zz-php.ini:
; Xdebug
[Xdebug]
xdebug.remote_enable=true
xdebug.remote_host="192.168.3.1" => this should be overwrited by HOST_IP
xdebug.remote_port="9001"
xdebug.idekey="XDEBUG_PHPSTORM"
This is the content of the script setup_xdebug_ip.sh:
#!/usr/bin/bash
sed -i -E "s/xdebug.remote_host.*/xdebug.remote_host=$HOST_IP/" /etc/php5/apache2/conf.d/zz-php.ini
Updated the script
I have updated the script to see it that's the reason why the value isn't changed and still not working. See the code below:
#!/usr/bin/bash
sed -ri "s/^xdebug.remote_host\s*=.*$//g" /etc/php5/apache2/conf.d/zz-php.ini
echo "xdebug.remote_host = $HOST_IP" >> /etc/php5/apache2/conf.d/zz-php.ini
In order to build the image and run the container I follow this steps:
Build the image:
docker build -t reynierpm/dev-php55 .
Run the container:
docker run -e HOST_IP=$(hostname -I | cut -d' ' -f1)
--name dev-php5
-it /bin/bash reynierpm/dev-php55
After the image gets built and the container is running I open a browser and point to: http://container_address/index.php (which contains phpinfo()) and I can see the value of xdebug.remote_host as 192.168.3.1 ...
why? What is not running when the container start? Why the value doesn't get overwritten using the provided value by -e on the run command?
UPDATE:
I've notice that I am only copying the file and setting up the permissions but I am not running it at all:
# Copy the script for change the xdebug.remote_host value based on HOST_IP
COPY /container-files/init-scripts/setup_xdebug_ip.sh /usr/local/bin/setup_xdebug_ip.sh
# Execute the script
RUN chmod +x /usr/local/bin/setup_xdebug_ip.sh
Could this be the issue? Everything that I put under /usr/local/bin is executed at container start? If not that's definitively the issue or at least I think.
UPDATE #2:
After the suggestions from #charles-dufly I've fixed a few things but still not working.
Now the Dockerfile looks like:
# This aims to be the default value if -e is not present on the run command
ENV HOST_IP=127.0.0.1
...
ADD container-files /
RUN chmod +x /usr/local/bin/setup_xdebug_ip && \
/usr/local/bin/setup_xdebug_ip && \
chmod +x /usr/local/bin/setup_php_settings && \
ln -s /etc/php5/mods-available/zz-php.ini /etc/php5/apache2/conf.d/zz-php.ini && \
ln -s /etc/php5/mods-available/zz-php-directories.ini /etc/php5/apache2/conf.d/zz-php-directories.ini && \
a2enmod rewrite
EXPOSE 80 9001
CMD ["/usr/local/bin/setup_php_settings"]
After build the image I am running the following command:
$ docker run -e HOST_IP=192.168.3.120 -p 80:80 --name php55-img-6 -it reynierpm/php5-dev-4 /bin/bash
I can see the value of xdebug.remote_host being set as 127.0.0.1 but is not taking the value passed as -e on the run command, why?
You're correct in that items under /usr/local/bin are not automatically executed.
The Filesystem Hierarchy Standard specifies /usr/local as a "tertiary hierarchy" with its own bin, lib, &c. subdirectories, equivalent in their intent and use to the like-named directories under / or /usr but for content installed local to the machine (in practice, this means software installed without the benefit of the local distro's packaging system).
If you want a command to be executed, you need a RUN that directly or indirectly invokes it.
As for the other matters discussed as this question has morphed, consider the following:
FROM alpine
ENV foo=bar
RUN echo $foo >/tmp/foo-value
CMD cat /tmp/foo-value; echo $foo
When invoked with:
docker run -e foo=qux
...this emits as output:
bar
qux
...because bar is the environment variable laid down by the RUN command, whereas qux is the environment variable as it exists at the CMD command's execution.
Thus, to ensure that an environment variable is honored in configuration, it must be read and applied during the CMD's execution, not during a prior RUN stage.
Multiple problems with your repo:
First of all when using CMD in docker file, the command added after the image name in the docker run : /bin/bash will override the CMD ["/usr/local/bin/setup_php_settings"] from your Dockerfile.
Thus your setup_php_settings is never executed!
You should use ENTRYPOINT i.s.o. CMD in your Dockerfile. I found good explanation here and here.
In conclusion for the Dockerfile change the CMD [...] line in:
ENTRYPOINT bash -C '/usr/local/bin/setup_php_settings';'bash'
then you can run your container with:
docker run -it -e HOST_IP=<your_ip_address> -e PHP_ERROR_REPORTING='E_ALL & ~E_STRICT' -p 80:80 --name dev-php5 mmi/dev-php55
No need to add /bin/bash at the end. Check-out test-repo for test-setup.
Secondly, in your /usr/local/bin/setup_php_settings, you should add
a2enmod rewrite
service apache2 restart
at the end, just before
source /etc/apache2/envvars && exec /usr/sbin/apache2 -DFOREGROUND`
this in order for your new settings to be applied in your web app.
If I include the following line in /root/.bashrc:
export $A = "AAA"
then when I run the docker container in interactive mode (docker run -i), the $A variable keeps its value. However if I run the container in detached mode I cannot access the variable. Even if I run the container explicitly sourcing the .bashrc like
docker run -d my_image /bin/bash -c "cd /root && source .bashrc && echo $A"
such line produces an empty output.
So, why is this happening? And how can I set the environment variables defined in the .bashrc file?
Any help would be very much appreciated!
The first problem is that the command you are running has $A being interpreted by your hosts shell (not the container shell). On your host, $A is likely black, so your effectively command becomes:
docker run -i my_image /bin/bash -c "cd /root && source .bashrc && echo "
Which does exactly as it says. We can escape the variable so it is sent to the container and properly evaluated there:
docker run -i my_image /bin/bash -c "echo \$A"
But this will also be blank because, although the container is, the shell is not in interactive mode. But we can force it to be:
docker run -i my_image /bin/bash -i -c "echo \$A"
Woohoo, we finally got our desired result. But with an added error from bash because there is no TTY. So, instead of interactive mode, we can just set a psuedo-TTY:
docker run -t my_image /bin/bash -i -c "echo \$A"
After running some tests, it appears that when running a container in detached mode, overidding the default environment variables doesnt always happen the way we want, depending on where you are in the Dockerfile.
As an exemple if, running a container in a detached container like so:
docker run **-d** --name image_name_container image_name
Whatever ENV variables you defined within the Dockerfile takes effect everywhere (read the rest and you will understand what the everywhere means).
example of a simple dockerfile (alpine is just a lighweight linux distribution):
FROM alpine:latest
#declaring a docker env variable and giving it a default value
ENV MY_ENV_VARIABLE dummy_value
#copying two dummy scripts into a place where i can execute them straight away
COPY ./start.sh /usr/sbin
COPY ./not_start.sh /usr/sbin
#in this script i could do: echo $MY_ENV_VARIABLE > /test1.txt
RUN not_start.sh
RUN echo $MY_ENV_VARIABLE > /test2.txt
#in this script i could do: echo $MY_ENV_VARIABLE > /test3.txt
ENTRYPOINT ["start.sh"]
Now if you want to run your container in detached and override some ENV variables, like so:
docker run **-d** -e MY_ENV_VARIABLE=new_value --name image_name_container image_name
Surprise! The var MY_ENV_VARIABLE is only overidden inside the script that is run in the ENTRYPOINT (and i checked, same thing happens if your replace ENTRYPOINT with CMD). It would also be overidden in a subscript that you could call from this start.sh script. But the MY_EV_VARIABLE variables that are called within a RUN dockerfile command or within the dockerfile itself do not get overidden.
In other words we would have $MY_ENV_VARIABLE being replaced by the value dummy_value and new_value depending on if you are in the ENTRYPOINT or not.