In earlier articleswe discovered the simplicity and usefulness of the ApacheBench load testing tool. The main reason behind this is that typically Docker containers are not built to accept additional parameters when launching. This makes it tricky to use a command-line tool within a container.
In the Dockerfilewe are simply using the ubuntu:latest image as our base container image, installing the apache2-utils package, and then defining that the command for this container is the ab command. Since this Docker container is planned to be used as an executor for the ab command, it makes sense to set the CMD instruction value to the ab command. However, if we run this container we will start to see an interesting difference between this container and other application containers.
Before we can run this container, however, we first need to build it. We can do so with the docker build command.
This CMD instruction is used to define what command the container should execute when launched. Since we defined that as the ab command without arguments, it executed the ab command without arguments. With abyou need to specify what URL you wish to test against.
Dockerfile: ENTRYPOINT vs CMD
What we can do in order to make this work is override the CMD instruction when we launch the container. We can do this by adding the command and arguments we wish to execute at the end of the docker run command. However, while we were successful, this process of overriding the CMD instruction is rather clunky. Sign up for a free Codeship Account hbspt. Instead, anything added to the end of the docker run command is appended to the command.
As the above example shows, we have now essentially turned our container into an executable. It looks like we are back to the same behavior as the CMD instruction.
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Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I am trying to execute a command inside my mongodb docker container. From my linux command prompt it is pretty easy and works when I do this. But I guess somehow docker thinks that now the binary file inside the container is not mongo or sth else and it gives me the following error:.
This calls the shell sh executing the script in quotation marks. This makes sense because you are quoting the parameter on the command line. Essentially when you did Next it will interpret the double-quotes and pass the entire inner contents now being mongo --eval 'rs. This should result in mongo looking for a program with the name mongo --eval 'rs. Which obviously doesn't exist. Learn more. Asked 2 years, 11 months ago. Active 1 year, 3 months ago. Viewed 10k times.
From my linux command prompt it is pretty easy and works when I do this docker exec -it dedfad mongo --eval 'rs. This works and gives me the output.San angelo
Server Fault is a question and answer site for system and network administrators. It only takes a minute to sign up. I assumed that this should work:. I don't understand. Why is that? Why first line is not the right way? In simple words. Just to note - the same was with command: directive in docker-compose. I believe the difference might have to do with, the the second command does shell processing, while the first does not. Per the official documentationthere is the exec and shell form, your first command is an exec form and it does not for instance expand environment variables, while the second one does.
So it is possible that, by using the exec form, the command might failing due to its dependence on shell processing. Note: Unlike the shell form, the exec form does not invoke a command shell. This means that normal shell processing does not happen. There is no separating of the command from the arguments by spaces, escaping of quotes, IO redirection, variable substitution, piping between commands, running multiple commands, etc, in the exec syscall.
The syscall only takes the executable to run and list of arguments to pass to that executable, and it runs it. If you switch to the string syntax of CMDdocker will run your command with a shell:. Note that I do not recommend running multiple commands this way inside of a container since there is no error handling if your first command fails, especially if it runs in the background.
You also leave a shell running as pid 1 inside the container which will break signal handling, resulting in a 10 second delay and ungraceful kill of your container by docker.
The signal handling can be mitigated by using the shell exec command:. However, handling processes silently failing in the background requires you switch to some kind of multi-process manager like supervisord, or preferably breakup your application into multiple containers and deploy them with something like docker-compose.
The second form works because all commands seperated with ";" are fed into sh command, which executes them. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 4 years, 11 months ago.Parse maillog
This image is primarily designed for development and ease of use, which is why I have created these shell scripts. I'm rather new to shell scripting, however I'd like to ensure my scripts are as robust as possible, is there anything I can do to improve their robustness?
From the comment in the code I don't understand it, and it's not used by any of the scripts. Either explain it better in the comment, or drop it, since you're not using it anyway. Sign up to join this community.
The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Shell script wrapper for Docker build and run Ask Question. Asked 3 years, 8 months ago.
Active 3 years, 8 months ago. Viewed 7k times. Jack Wilsdon Jack Wilsdon 1, 3 3 gold badges 17 17 silver badges 31 31 bronze badges.
Active Oldest Votes. Honestly I only have nitpicks. I didn't know you could omit the quotes for empty variables, cool! Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Featured on Meta. Community and Moderator guidelines for escalating issues via new response…. Feedback on Q2 Community Roadmap. Related 4. Hot Network Questions.
Question feed.Shell Spscript parameters are the entities that are used to store variables in Shell. Among these parameters, the named spaces are there in the memory and they permit us to access these stored variables.
Generally, there are two types of parameters. They are called variables and special parameters. A parameter can be an argument or a variable can be called as a parameter even though it is not used as part of a command argument.
Special parameters are pre-set by the shell and these parameters are read-only. The variables are managed by the shell or by the users. To add additional features to the command while working with shell script can be achieved by using parameters i. Parameters are used to help in choosing options from the command line. For example, we can use the parameters to have an interactive command line to display a particular file name and can perform operations such as overriding it or just simply to check if the file exists or not.Docker Commands With Examples - Docker Tutorial - DevOps Tutorial - Docker Training - Edureka
Also, we can read the content of a shell script by the use of positional parameters. One of the main advantages of using the parameters is that while passing the arguments to the function or a script, the code can be reused again and again.
Also with the usage of the parameters, the command line arguments can be used by shifting the position of the arguments. The advantage of passing the arguments improves security as there is no need for parsing the environment variables. Also, it adds flexibility where many shell interpreters can be used.
The shell script parameters help in performing effective and flexible scripting with many added features. Such features are parameter expansion; advanced tests along with double square brackets which can be used as pattern matching. Also, parameter manipulation and arithmetic operations can be done very easily.
This is a guide to Shell Script Parameters. Here we discuss shell script parameters with examples, advantages and its rules and regulations. Your email address will not be published. Forgot Password? Popular Course in this category. Course Price View Course. Leave a Reply Cancel reply Your email address will not be published. Free Software Development Course.
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. I have following Dockerfile where I am trying to call.
PS1 file with the parameter so user can provided value against it during Docker Run command. I am trying to run below Docker run command once the image is built. But it fails to pass the value to ps1 file. I have used environment variable within docker file and read the value of it in Powershell.
I forgot to update this issue, I have defined environment variables in docker file and read their values in powershell, that solves my problem. I'm in need of similar solution and fairly new to Docker. I've been searching around for almost 2 days now trying to figure out how to get this to work, and wow, I'm grateful to have come across this thread Here's an example of how I'm passing in environment variables which are then passed in as arguments to.
Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. New issue. Jump to bottom. Trying to call PS1 file with the parameters from within Docker file, but no luck.
Labels question. Copy link Quote reply. Hi, I have following Dockerfile where I am trying to call. This comment has been minimized. Sign in to view. RUN powershell -File. Sign up for free to join this conversation on GitHub.
How do I approach doing this? Common ways of dealing with this involve shell commands getopts and shift. You pass the arguments just like you would with any other command. With this structure, we don't rely on the order of the parameters, as we're defining a key letter to each one of them.
Also, the help function will be printed all the times that the parameters are defined wrongly. It's very useful when we have a lot of scripts with different parameters to handle. It works as the following:. More on shell arguments. The arg delimiter is whitespace, but can be changed. Don't remember how off-hand. Then use. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered.
How can I pass a command line argument into a shell script?Bmc password
Ask Question. Asked 8 years, 2 months ago. Active 22 days ago. Viewed 1.
Docker RUN vs CMD vs ENTRYPOINT
Paul Paul 5, 10 10 gold badges 25 25 silver badges 29 29 bronze badges. Active Oldest Votes. Bruce Ediger Bruce Ediger Becker Feb 10 '12 at Kevin Kevin
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