Introduction to Buildah: A CLI Tool For Building Images

Buildah is a tool for through a . Similar to Podman, Buildah doesn't depend on a daemon such as Docker or CRI-O, and it doesn't require root privileges. . This allows you to issue Buildah commands from a scripting language such as Bash. building OCI-compatible images lower-level coreutils interface Buildah provides a command-line tool that replicates all the commands found in a Dockerfile This tutorial shows you how to: Use Buildah to package a web-application as a container starting from an existing image, and then run your application with Podman and Docker Use Buildah to package a web-application as a container starting from scratch Use Buildah to package a web-application as a container starting from a Dockerfile Use Buildah to modify an existing container image Push images to a public repository Prerequisites In this tutorial, we assume basic familiarity with or . To learn about Podman, see our tutorial. Docker Podman Podman for Docker Users . Use the command to verify if is installed: Buildah buildah --version Buildah buildah --version The following example output shows that Buildah is installed on your computer: buildah version 1.11.6 (image-spec 1.0.1-dev, runtime-spec 1.0.1-dev) If Buildah is not installed, follow the instructions from the page. Buildah Install . Enter the following command to check if is installed on your system: Podman Podman podman version The following example output shows that Podman is installed on your computer: buildah version 1.11.6 (image-spec 1.0.1-dev, runtime-spec 1.0.1-dev) If Buildah is not installed, follow the instructions from the page. Buildah Install . Enter the following command to check if is installed on your system: Podman Podman podman version The following example output shows that Podman is installed on your computer: Version: 1.6.4 RemoteAPI Version: 1 Go Version: go1.12.12 OS/Arch: linux/amd64 Refer the page for details on how to install Podman. Podman Installation Instructions . Use the following command to see if Docker is installed on your system: Docker docker --version The following example output shows that Docker is installed on your computer: Docker version 18.06.3-ce, build d7080c1 For details about installing Docker, refer to the . Install Docker page Package a Web-based Application as a Container Starting from an Existing Image In this section, you'll use Buildah to package a web-based application as a container, starting from the image. Then, you'll run your container image with . Alpine Linux Podman and Docker is only in size, and it lacks several prerequisites that are required to run . Thus, you'll use to install these prerequisites. Alpine Linux 5 MB ExpressJS apk 1. Enter the following command to create a new container image based on the image, and store the name of your new image in an environment variable named : alpine container container=$(buildah from alpine) Getting image signatures Copying blob c9b1b535fdd9 skipped: already exists Copying config e7d92cdc71 Writing manifest to image destination Storing signatures source done ☞ Note that, by default, Buildah constructs the name of the container by appending to the name: -working-container echo $container alpine-working-container You can override the default behavior by specifying the --name flag with the name of the working container. The following example creates a container image called : example-container example_container=$(buildah from --name alpine) "example-container" echo $example_container example-container 2. The Alpine Linux image you just pulled is only 5 MB in size and it lacks the basic utilities such as Bash. Run the following command to verify your new container image: buildah run bash $container The following output shows that the container image has been created, but bash is not yet installed: ERRO[0000] container_linux.go:346: starting container process caused container_linux.go:346: starting container process caused error running container: error creating container [bash]: : status 1 ERRO status 1 "exec: \"bash\": executable file not found in " $PATH "exec: \"bash\": executable file not found in " $PATH for exit exit 3. To install Bash, enter the command and specify: buildah run The name of the container ( ) $container Two dashes. The commands after are passed directly to the container. -- The command you want to execute inside the container ( ) apk add bash buildah run -- apk add bash $container fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/main/x86_64/APKINDEX.tar.gz fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/community/x86_64/APKINDEX.tar.gz (1/5) Installing ncurses-terminfo-base (6.1_p20191130-r0) (2/5) Installing ncurses-terminfo (6.1_p20191130-r0) (3/5) Installing ncurses-libs (6.1_p20191130-r0) (4/5) Installing readline (8.0.1-r0) (5/5) Installing bash (5.0.11-r1) Executing bash-5.0.11-r1.post-install Executing busybox-1.31.1-r9.trigger OK: 15 MiB 19 packages in 4. Similarly to how you've installed , run the command to install and : bash buildah run node npm buildah run -- apk add --update nodejs nodejs-npm $container fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/main/x86_64/APKINDEX.tar.gz fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/community/x86_64/APKINDEX.tar.gz (1/8) Installing ca-certificates (20191127-r1) (2/8) Installing c-ares (1.15.0-r0) (3/8) Installing libgcc (9.2.0-r3) (4/8) Installing nghttp2-libs (1.40.0-r0) (5/8) Installing libstdc++ (9.2.0-r3) (6/8) Installing libuv (1.34.0-r0) (7/8) Installing nodejs (12.15.0-r1) (8/8) Installing npm (12.15.0-r1) Executing busybox-1.31.1-r9.trigger Executing ca-certificates-20191127-r1.trigger OK: 73 MiB 27 packages in 5. You can use the command to set the image configuration values. The following command sets the working directory to : buildah config /usr/src/app/ buildah config --workingdir /usr/src/app/ $container 6. To initialize a new JavaScript project, run the command inside the container: npm init -y buildah run -- npm init -y $container Wrote to /package.json: { : , : , : , : , : { : }, : {}, : {}, : { : }, : [], : , : } "name" "" "version" "1.0.0" "description" "" "main" "index.js" "directories" "lib" "lib" "dependencies" "devDependencies" "scripts" "test" "echo \"Error: no test specified\" && exit 1" "keywords" "author" "" "license" "ISC" 7. Issue the following command to install Express.JS: buildah run -- npm install express --save $container npm WARN @1.0.0 No description npm WARN @1.0.0 No repository field. + express@4.17.1 added 1 package from 8 contributors and audited 126 packages 1.553s found 0 vulnerabilities in 8. Create a file named and copy in the following JavaScript source code: HelloWorld.js const express = require( ) const app = express() const port = 3000 app.get( , (req, res) => res.send( )) app.listen(port, () => console.log(`Example app listening on port !`)) 'express' '/' 'Hello World!' ${port} 9. To copy the file to your container's working directory, enter the command specifying: HelloWorld.js buildah copy The name of the container ( ) $container The name of the file you want to copy ( ) HelloWorld.js buildah copy HelloWorld.js $container c26df5d060c589bda460c34d40c3e8f47f1e401cdf41b379247d23eca24b1c1d ☞ You can copy a file to a different container by passing the name of the destination directory as an argument. The following example command copies the to the directory: HelloWorld.js /temp buildah copy HelloWorld.js /temp $container 10. To set the entry point for your container, enter the command with the argument: buildah config --entrypoint buildah config --entrypoint "node HelloWorld.js" $container 11. At this point, you're ready to write the new image using the command. It takes two parameters: buildah commit The name of the container image ( ) $container The name of the new image ( ) buildah-hello-world buildah commit buildah-hello-world $container Getting image signatures Copying blob 5216338b40a7 skipped: already exists Copying blob 821cca548ffe Copying config 0d9f23545e Writing manifest to image destination Storing signatures 0d9f23545ed69ace9be47ed081c98b4ae182801b7fe5b7ef00a49168d65cf4e5 source done done ☞ If the provided image name doesn't begin with a registry name, Buildah defaults to adding to the name of the image. localhost 12. The following command lists your Buildah images: buildah images REPOSITORY TAG IMAGE ID CREATED SIZE localhost/buildah-hello-world latest 0d9f23545ed6 56 seconds ago 71.3 MB Running Your Buildah Image with Podman 1. To run your image with Podman, you must first make sure your image is visible in Podman: podman images The following example output shows the container image created in the previous steps: REPOSITORY TAG IMAGE ID CREATED SIZE localhost/buildah-hello-world latest 0d9f23545ed6 About a minute ago 71.3 MB 2. Run the image by entering the command with the following arguments: buildah-hello-world podman run to specify that the container should be run in the background, and that Podman should allocate a pseudo-TTY for it. dt with the port on host (3000) that'll be forwarded to the container port (3000), separated by . -p : The name of your image ( ) buildah-hello-world podman run -dt -p 3000:3000 buildah-hello-world 332d060fc0009a8088349aba672be3601b76553e5df7643d4788c917528cbd8e 3. Use the command to see the list of running containers: podman ps podman ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 332d060fc000 localhost/buildah-hello-world:latest /bin/sh 23 seconds ago Up 21 seconds ago 0.0.0.0:3000->3000/tcp cool_ritchie 4. To see the running application, point your browser to . The application should look as shown in the following screenshot: http://localhost:3000 5. Now that the functionality of the application has been validated, you can stop the running container: podman 332d060fc000 kill 332d060fc000 Running Your Buildah Image with Docker The container image you've built in previous sections is compatible with Docker. In this section, we'll walk you through the steps required to run the image with Docker. buildah-hello-world 1. First, you must push the image to Docker. Enter the command specifying: buildah push The name of the container The destination which uses the following format . : The following example command uses the transport to push the image to Docker: docker-daemon buildah-hello-world buildah push buildah-hello-world docker-daemon:buildah-hello-world:latest Getting image signatures Copying blob 5216338b40a7 Copying blob 821cca548ffe Copying config 0d9f23545e Writing manifest to image destination Storing signatures source done done done 2. List the Docker images stored on your local machine: docker images REPOSITORY TAG IMAGE ID CREATED SIZE buildah-hello-world latest 0d9f23545ed6 16 minutes ago 64.5MB 3. Run the container image with Docker: buildah-hello-world docker run -dt -p 3000:3000 buildah-hello-world b0f29ff964cd84bf204b3f30f615581c4bb67c4a880aa871ce9c89db48e68720 4. After a few seconds, enter the image to display the list of running containers: docker ps docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES b0f29ff964cd buildah-hello-world 16 seconds ago Up 13 seconds 0.0.0.0:3000->3000/tcp goofy_chandrasekhar "/bin/sh -c 'node He…" 5. To see the running application, point your browser to . The application should look as shown in the following screenshot: http://localhost:3000 6. Stop the running container with: docker b0f29ff964cd kill b0f29ff964cd Package a Web-application as a Container Starting from Scratch With Buildah, you can start from an image that's basically an empty shell, except for some container metadata. Once you create such an image, you can then add more packages to it. This is useful when you want to create small containers, with a minimum number of packages installed. In this section, you'll build the application starting from scratch. HelloWorld An empty container image doesn't have , , or any other tools installed. Thus, to install Node and Express.JS on it, you'll mount the container's file-system to a directory on the host, and then use the host's package management system to install the required packages. bash yum 1. If you're running Buildah as an unprivileged user, mounting the container's file-system will fail unless you enter the user namespace with the following command: buildah unshare 2. To start building from an empty container image, enter the command, and specify scratch as an argument: buildah from container=$(buildah from scratch) ☞ Note that the above command stores the name of your container image in the container environment variable: echo $container working-container-1 3. Issue the following command to mount the container filesystem to a directory on the host, and store the path of the directory in the environment variable: buildah mount mnt mnt=$(buildah mount ) $container 4. Use the command to see the name of the directory where the container filesystem is mounted: echo echo $mnt /home/vagrant/. /share/containers/storage/overlay/e1df4ce46bb88907af45e4edb7379fac8781928ac0cafe0c1a6fc799f4f7a48b/merged local 5. You can check that the container filesystem is empty with: ls $mnt [root@localhost ~] # 6. Use the hosts' package manager to install software into the container. Enter the command specifying the following arguments: yum install to configure the alternative install root directory ( ). The packages will be installed relative to this directory. --installroot mnt to indicate the version you want to install the packages for. Our example uses . --releasever centos-release-8 The name of the packages you want to install ( and ). bash coreutils The flag to automatically answer to all questions. -y yes yum install --releasever=centos-release-8 --installroot bash coreutils -y $mnt shadow-utils-2:4.6-8.el8.x86_64 systemd-239-18.el8_1.2.x86_64 systemd-libs-239-18.el8_1.2.x86_64 systemd-pam-239-18.el8_1.2.x86_64 systemd-udev-239-18.el8_1.2.x86_64 trousers-lib-0.3.14-4.el8.x86_64 tzdata-2019c-1.el8.noarch util-linux-2.32.1-17.el8.x86_64 -2.21-10.el8.x86_64 xz-5.2.4-3.el8.x86_64 xz-libs-5.2.4-3.el8.x86_64 zlib-1.2.11-10.el8.x86_64 Complete! which Note that the above output was truncated for brevity. 7. Clean up the temporary files that created as follows: yum yum clean --installroot all $mnt 24 files removed 8. Validate the functionality of your container image. Enter the following command to run inside of the container: buildah run bash buildah run bash $container bash-4.4 # 9. You can issue a few commands to make sure everything works as expected. Once you're done, enter the command to terminate the session: exit bash exit 10. Enter the following commands to move into the directory where you mounted the container's filesystem, and then download the Node.JS installer: && wget https://nodejs.org/dist/v12.16.1/node-v12.16.1-linux-x64.tar.xz cd $mnt --2020-02-24 13:50:07-- https://nodejs.org/dist/v12.16.1/node-v12.16.1-linux-x64.tar.xz Resolving nodejs.org (nodejs.org)... 104.20.22.46, 104.20.23.46, 2606:4700:10::6814:162e, ... Connecting to nodejs.org (nodejs.org)|104.20.22.46|:443... connected. HTTP request sent, awaiting response... 200 OK Length: 14591852 (14M) [application/x-xz] Saving to: node-v12.16.1-linux-x 100%[=======================>] 13.92M 7.25MB/s 1.9s 2020-02-24 13:50:09 (7.25 MB/s) - saved [14591852/14591852] 'node-v12.16.1-linux-x64.tar.xz' in 'node-v12.16.1-linux-x64.tar.xz' 11. To extract the files from the archive file and remove the first component from the file names, run the command with : tar xf --strip-commponents=1 tar xf node-v12.16.1-linux-x64.tar.xz --strip-components=1 12. Delete the archive: rm -f node-v12.16.1-linux-x64.tar.xz 13. To make sure everything works as expected, use the command to run inside of the container: buildah run node buildah run node $container Welcome to Node.js v12.16.1. Type more information. > ".help" for 14. Type to exit the Node.JS interactive shell. 15. Now that everything is set up, you can install Express.JS and create the project. Follow the steps from to from the section. .exit HelloWorld 4 9 "Build an Express.JS based Image from an Existing Image" 16. Once you've finished the above steps, unmount the container filesystem: buildah unmount $container 17. Execute the command to create a new image called : buildah commit buildah-demo-from-scratch buildah commit buildah-demo-from-scratch $container Getting image signatures Copying blob a9a2ac73e013 Copying config ec14304d59 Writing manifest to image destination Storing signatures ec14304d5906c7b8fb9a485ff959e4a6c337115245a827858bf6ba808f5f4e0e source done done 18. To see the list of your Buildah images, run the command: buildah images buildah images REPOSITORY TAG IMAGE ID CREATED SIZE localhost/buildah-demo-from-scratch latest ec14304d5906 3 minutes ago 582 MB 19. You can use the command to retrieve more details about the container image: buildah inspect buildah-demo-from-scratch buildah inspect $container { : , : , : , : , : , : , : , : , : , : , : , : null, : , : { : , : , : , : { : [ , , ], : }, : { : , : null } }, : { : , : { : , : , : , : , : , : , : , : , : , : null, : null, : , : null, : , : [ , , ], : [], : null }, : { : , : , : , : , : , : , : , : , : , : null, : null, : , : null, : , : [ , , ], : [], : null }, : , : }, : , : , : [ { : , : , : }, { : , : , : }, { : , : , : }, { : , : , : }, { : , : , : }, { : , : , : }, { : , : , : } ], : , : , : , : { : , : , : [], : [] }, : [ , , , , , , , , , , , , ], : [], : [], : [ { : } ], : [] } "Type" "buildah 0.0.1" "FromImage" "" "FromImageID" "" "FromImageDigest" "" "Config" "" "Manifest" "" "Container" "working-container" "ContainerID" "f974b8b06921a57edddb5735ee7fc0c7176051ff1b76d0523bf2879d7865afba" "MountPoint" "" "ProcessLabel" "system_u:system_r:container_t:s0:c435,c738" "MountLabel" "system_u:object_r:container_file_t:s0:c435,c738" "ImageAnnotations" "ImageCreatedBy" "" "OCIv1" "created" "2020-02-27T14:46:38.379626079Z" "architecture" "amd64" "os" "linux" "config" "Entrypoint" "/bin/sh" "-c" "node HelloWorld.js" "WorkingDir" "/usr/src/app/" "rootfs" "type" "" "diff_ids" "Docker" "created" "2020-02-27T14:46:38.379626079Z" "container_config" "Hostname" "" "Domainname" "" "User" "" "AttachStdin" false "AttachStdout" false "AttachStderr" false "Tty" false "OpenStdin" false "StdinOnce" false "Env" "Cmd" "Image" "" "Volumes" "WorkingDir" "/usr/src/app/" "Entrypoint" "/bin/sh" "-c" "node HelloWorld.js" "OnBuild" "Labels" "config" "Hostname" "" "Domainname" "" "User" "" "AttachStdin" false "AttachStdout" false "AttachStderr" false "Tty" false "OpenStdin" false "StdinOnce" false "Env" "Cmd" "Image" "" "Volumes" "WorkingDir" "/usr/src/app/" "Entrypoint" "/bin/sh" "-c" "node HelloWorld.js" "OnBuild" "Labels" "architecture" "amd64" "os" "linux" "DefaultMountsFilePath" "" "Isolation" "IsolationOCIRootless" "NamespaceOptions" "Name" "cgroup" "Host" true "Path" "" "Name" "ipc" "Host" false "Path" "" "Name" "mount" "Host" false "Path" "" "Name" "network" "Host" true "Path" "" "Name" "pid" "Host" false "Path" "" "Name" "user" "Host" true "Path" "" "Name" "uts" "Host" false "Path" "" "ConfigureNetwork" "NetworkDefault" "CNIPluginPath" "/usr/libexec/cni:/opt/cni/bin" "CNIConfigDir" "/etc/cni/net.d" "IDMappingOptions" "HostUIDMapping" true "HostGIDMapping" true "UIDMap" "GIDMap" "DefaultCapabilities" "CAP_AUDIT_WRITE" "CAP_CHOWN" "CAP_DAC_OVERRIDE" "CAP_FOWNER" "CAP_FSETID" "CAP_KILL" "CAP_MKNOD" "CAP_NET_BIND_SERVICE" "CAP_SETFCAP" "CAP_SETGID" "CAP_SETPCAP" "CAP_SETUID" "CAP_SYS_CHROOT" "AddCapabilities" "DropCapabilities" "History" "created" "2020-02-27T14:56:04.319174231Z" "Devices" 20. The steps for running the image are similar to the ones from the . For the sake of brevity, those steps are not repeated here. "Running your Buildah Image with Podman" Package a Web-application as a Container Starting from a Dockerfile 1. Create a directory called and then move into it: from-dockerfile mkdir from-dockerfile && from-dockerfile/ cd 2. Use a plain-text editor to create a file called , and copy in the following snippet: Dockerfile FROM node:10 WORKDIR /usr/src/app RUN npm init -y RUN npm install express --save COPY HelloWorld.js . CMD [ , ] "node" "HelloWorld.js" 3. Create a file named with the following content: HelloWorld.js const express = require( ) const app = express() const port = 3000 app.get( , (req, res) => res.send( )) app.listen(port, () => console.log(`Example app listening on port !`)) 'express' '/' 'Hello World!' ${port} 4. Build the container image. Enter the buildah bud command specifying the -t flag with the name Buildah should apply to the built image, and the build context directory ( ): . buildah bud -t buildah-from-dockerfile . STEP 1: FROM node:10 STEP 2: WORKDIR /usr/src/app STEP 3: RUN npm init -y Wrote to /usr/src/app/package.json: { : , : , : , : , : { : }, : [], : , : } STEP 4: RUN npm install express --save npm notice created a lockfile as package-lock.json. You should commit this file. npm WARN app@1.0.0 No description npm WARN app@1.0.0 No repository field. + express@4.17.1 added 50 packages from 37 contributors and audited 126 packages 4.989s found 0 vulnerabilities STEP 5: COPY HelloWorld.js . STEP 6: CMD [ , ] STEP 7: COMMIT buildah-from-dockerfile Getting image signatures Copying blob 7948c3e5790c skipped: already exists Copying blob 4d1ab3827f6b skipped: already exists Copying blob 69dfa7bd7a92 skipped: already exists Copying blob 01727b1a72df skipped: already exists Copying blob 1d7382716a27 skipped: already exists Copying blob 03dc1830d2d5 skipped: already exists Copying blob 1e1795dd2c10 skipped: already exists Copying blob c8a8d3d42bc1 skipped: already exists Copying blob 072dcfd76a1e skipped: already exists Copying blob fc67e152fd86 Copying config 7619bf0e33 Writing manifest to image destination Storing signatures 7619bf0e33165f5c3dc6da00cb101f2195484bff3e59f4c6f57a41c07647d407 7619bf0e33165f5c3dc6da00cb101f2195484bff3e59f4c6f57a41c07647d407 "name" "app" "version" "1.0.0" "description" "" "main" "index.js" "scripts" "test" "echo \"Error: no test specified\" && exit 1" "keywords" "author" "" "license" "ISC" in "node" "HelloWorld.js" source done done 5. The following command lists your Buildah images: buildah images REPOSITORY TAG IMAGE ID CREATED SIZE localhost/buildah-from-dockerfile latest 7619bf0e3316 52 seconds ago 944 MB 6. Enter the command to run un the image: podman run buildah-from-dockerfile podman run -dt -p 3000:3000 buildah-from-dockerfile dbbae173dca0ca5b602c0b9a70055886381cb7df5ae25fbb4bd81c75a4bcb50d [vagrant@localhost buildah-hello-world]$ podman ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES dbbae173dca0 localhost/buildah-from-dockerfile:latest node HelloWorld.j... 4 seconds ago Up 3 seconds ago 0.0.0.0:3000->3000/tcp priceless_cartwright 7. Point your browser to , and you should see something similar to the following screenshot: http://localhost:3000 8. Stop the container by entering the command followed by the identifier of the container ( ): podman kill buildah-from-dockerfile dbbae173dca0 podman dbbae173dca0 kill dbbae173dca0ca5b602c0b9a70055886381cb7df5ae25fbb4bd81c75a4bcb50d Use Buildah to Modify a Container Image With Buidah, you can modify a container in the following ways: Mount the container and copy files to it Using the buildah config command Using the buildah copy command Mount the Container and Copy Files to It 1. Run the following command to create a new container using the image as a starting point: buildah-from-dockerfile buildah from buildah-from-dockerfile The above command prints the name of your new container: buildah-from-dockerfile-working-container 2. Use the command to see the list of your working containers: buildah list buildah containers CONTAINER ID BUILDER IMAGE ID IMAGE NAME CONTAINER NAME 78c4225c8c37 * 7619bf0e3316 localhost/buildah-from-docker... buildah-from-dockerfile-working-container 3. If you're running Buildah as an unprivileged user, enter the user namespace with: buildah unshare 4. Mount the container filesystem to a directory on the host, and save the name of that directory in an environment variable called by entering the following command: mount mount=$(buildah mount buildah-from-dockerfile-working-container) 5. You can use the command to print the path of the folder where the container filesystem is mounted: echo echo $mount /home/vagrant/. /share/containers/storage/overlay/83b2d731b920653a569795cf75f4902a1e148dab61f4cb41bcc37bae0f5d6655/merged local 6. Move into the folder: /usr/src/app /usr/src/app/ cd $mount 7. Open the file in a plain-text editor, and edit the line that prints the message to: HelloWorld.js Hello World! app.get( , (req, res) => res.send( )) '/' 'Hello World (modified with Buildah)!' Your file should look similar to the listing below: HelloWorld.js cat HelloWorld.js const express = require( ) const app = express() const port = 3000 app.get( , (req, res) => res.send( )) app.listen(port, () => console.log(`Example app listening on port !`)) 'express' '/' 'Hello World (modified with Buildah)!' ${port} 8. Save the changes to a new container image called : modified-container buildah commit buildah-from-dockerfile-working-container modified-container Getting image signatures Copying blob 7948c3e5790c skipped: already exists Copying blob 4d1ab3827f6b skipped: already exists Copying blob 69dfa7bd7a92 skipped: already exists Copying blob 01727b1a72df skipped: already exists Copying blob 1d7382716a27 skipped: already exists Copying blob 03dc1830d2d5 skipped: already exists Copying blob 1e1795dd2c10 skipped: already exists Copying blob c8a8d3d42bc1 skipped: already exists Copying blob 072dcfd76a1e skipped: already exists Copying blob fc67e152fd86 skipped: already exists Copying blob a546faf200ff Copying config d3ac43ac8d Writing manifest to image destination Storing signatures d3ac43ac8da20aef987367353e56e22a1a2330176c08e255c72670b3b08c1e14 source done done 9. If you run the command, you should see both images: buildah images buildah images REPOSITORY TAG IMAGE ID CREATED SIZE localhost/modified-container latest d3ac43ac8da2 46 seconds ago 944 MB localhost/buildah-from-dockerfile latest 7619bf0e3316 14 minutes ago 944 MB 10. Unmount the root filesystem of your container by entering the following command: buildah unmount buildah unmount buildah-from-dockerfile-working-container 78c4225c8c377d8a018583586e2f76932204f20b4f3621fedb1ab3d41f8a3240 11. Run the image with Podman: modified-container podman run -dt -p 3000:3000 modified-container 70105ac094b672c98f56290d25fa5406a7c51bf401cff586c7a356b4f19f1320 12. Enter the command to print the list of running containers: podman ps podman ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 70105ac094b6 localhost/modified-container:latest node HelloWorld.j... 4 seconds ago Up 4 seconds ago 0.0.0.0:3000->3000/tcp pedantic_rhodes 13. To see the modified application in action, point your browser to : http://localhost:3000 Modify a Container with the Command buildah config 1. To see the list of your local container images, use the command: buildah images buildah containers CONTAINER ID BUILDER IMAGE ID IMAGE NAME CONTAINER NAME 305591a5116c * 7619bf0e3316 localhost/buildah-from-docker... buildah-from-dockerfile-working-container 2. In this example, you'll modify the configuration value for the field. Run the command specifying the following parameters: author buildah config with the name of the author. --author The identifier of the container ( ) 305591a5116c buildah config --author= 305591a5116c 'Andrei Popescu' 3. Enter the command to display detailed information about your container: buildah inspect buildah inspect 305591a5116c { : { : , : { : , : , : , : , : , : , : , : , : , : [ , , ], : [ , ], : , : null, : , : [ ], : [], : null }, : , : { : , : , : , : , : , : , : , : , : , : [ , , ], : [ , ], : , : null, : , : [ ], : [], : null }, "Docker" "created" "2020-02-24T14:41:01.41295511Z" "container_config" "Hostname" "" "Domainname" "" "User" "" "AttachStdin" false "AttachStdout" false "AttachStderr" false "Tty" false "OpenStdin" false "StdinOnce" false "Env" "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" "NODE_VERSION=10.19.0" "YARN_VERSION=1.21.1" "Cmd" "node" "HelloWorld.js" "Image" "" "Volumes" "WorkingDir" "/usr/src/app" "Entrypoint" "docker-entrypoint.sh" "OnBuild" "Labels" "author" "Andrei Popescu" "config" "Hostname" "" "Domainname" "" "User" "" "AttachStdin" false "AttachStdout" false "AttachStderr" false "Tty" false "OpenStdin" false "StdinOnce" false "Env" "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" "NODE_VERSION=10.19.0" "YARN_VERSION=1.21.1" "Cmd" "node" "HelloWorld.js" "Image" "" "Volumes" "WorkingDir" "/usr/src/app" "Entrypoint" "docker-entrypoint.sh" "OnBuild" "Labels" Note that that the above output was truncated for brevity. As you can see, the field has been updated: author : , "author" "Andrei Popescu" Modifying a Container with the Command buildah copy 1. List your Buildah images with: buildah images REPOSITORY TAG IMAGE ID CREATED SIZE localhost/buildah-from-dockerfile latest 4c4c1019785e 19 seconds ago 944 MB docker.io/library/node 10 aa6432763c11 5 days ago 940 MB 2. Create a new working container using as the starting image: buildah-from-dockerfile container=$(buildah from buildah-from-dockerfile) 3. The above command saves the name of your new working container into an environment variable called . Use the command to see the name of your new container: container echo echo $container buildah-from-dockerfile-working-container 4. Use a plain-text editor to open the . Next, modify the line of code that prints the message to the following: HelloWorld.js Hello World! app.get( , (req, res) => res.send( )) '/' 'Hello World (modified with the buildah copy command)!' Your file should look similar to the following listing: HelloWorld.js const express = require( ) const app = express() const port = 3000 app.get( , (req, res) => res.send( )) app.listen(port, () => console.log(`Example app listening on port !`)) 'express' '/' 'Hello World (modified with the buildah copy command)!' ${port} 5. Enter the following command to copy the content of the file into the container's directory: buildah copy HelloWorld.js /usr/src/app/ buildah copy buildah-from-dockerfile-working-container HelloWorld.js /usr/src/app/ bf36dd7b6ba5d3f520835f5e850e4303bd830bd0934d1cb8a11c4c45cf3ebcb8 6. The is different from the command. Since Buildah is a tool aimed at building images, you can't use to map ports or mount volumes. You can think of it as similar to the command from a Dockerfile. Thus, to test the changes before saving them to a new image, you must run a shell inside of the container: buildah run podman run buildah run RUN buildah run -- bash $container 7. Use the command to list the contents of the file: cat HelloWorld.js cat HelloWorld.js const express = require( ) const app = express() const port = 3000 app.get( , (req, res) => res.send( )) app.listen(port, () => console.log(`Example app listening on port !`)) 'express' '/' 'Hello World (modified with the buildah copy command)!' ${port} 8. Type to return to the host: exit exit 9. Save your changes to a new container image named . Enter the command passing it the following parameters: modified-with-copy buildah commit The name of your working container ( ) $container The name of your new container ( ) modified-with-copy buildah commit modified-with-copy $container Getting image signatures Copying blob 2c995a2087c1 skipped: already exists Copying blob 00adafc8e77b skipped: already exists Copying blob d040e6423b7a skipped: already exists Copying blob 162804eaaa1e skipped: already exists Copying blob 91daf9fc6311 skipped: already exists Copying blob 236d3097407d skipped: already exists Copying blob 92086f81cd8d skipped: already exists Copying blob 90aa9e20811b skipped: already exists Copying blob cea8dd7dcda1 skipped: already exists Copying blob 490adad7924f skipped: already exists Copying blob fc29e33720c1 Copying config c6df996bc7 Writing manifest to image destination Storing signatures c6df996bc740c9670c87470f65124f8a8a3b74ecde3dc38038530a98209e5148 source done done 10. Enter the command to list the images available on your system: podman images podman images podman images REPOSITORY TAG IMAGE ID CREATED SIZE localhost/modified-with-copy latest c6df996bc740 About a minute ago 944 MB localhost/buildah-from-dockerfile latest efd9caedf198 24 minutes ago 944 MB docker.io/library/node 10 aa6432763c11 5 days ago 940 MB 11. Run the modified image with Podman: podman run -dt -p 3000:3000 modified-with-copy f2bf06e4d6010adab6acf92db063a4c11f821fb96c2912266ac9900752f53bc4 12. Make sure that the modified container works as expected by pointing your browser to : http://localhost:3000 Use Buildah to Push an Image to a Public Repository In this section, we'll show how you can push a Buildah image to Quay.io. Then, you'll use Docker to pull and run it on your system. 1. Login to Quay.io with the following command: buildah login quay.io Buildah will prompt you to enter your username and password: Username: Password: Login Succeeded! 2. Use the command to see the list of Buildah images available on your system: buildah images buildah images REPOSITORY TAG IMAGE ID CREATED SIZE localhost/modified-with-copy latest c6df996bc740 31 minutes ago 944 MB localhost/buildah-from-dockerfile latest efd9caedf198 54 minutes ago 944 MB docker.io/library/node 10 aa6432763c11 5 days ago 940 MB 3. To push an image to Quay.io, enter the command specifying: buildah push The source. The destination. This uses the following format . : The following example command pushes the to the repository: modified-with-copy andreipope/modified-with-copy buildah push modified-with-copy docker://quay.io/andreipope/modified-with-copy:latest Getting image signatures Copying blob d040e6423b7a Copying blob 236d3097407d Copying blob 2c995a2087c1 Copying blob 00adafc8e77b skipped: already exists Copying blob 91daf9fc6311 Copying blob 162804eaaa1e Copying blob 92086f81cd8d skipped: already exists Copying blob 90aa9e20811b skipped: already exists Copying blob cea8dd7dcda1 skipped: already exists Copying blob 490adad7924f skipped: already exists Copying blob fc29e33720c1 skipped: already exists Copying config c6df996bc7 Writing manifest to image destination Copying config c6df996bc7 Writing manifest to image destination Writing manifest to image destination Storing signatures source done done done done done done done 4. Pull the image from Quay.io using the command: docker pull docker pull quay.io/andreipope/modified-with-copy:latest latest: Pulling from andreipope/modified-with-copy 571444490ac9: Pull complete a8c44c6007c2: Pull complete 78082700aa2c: Pull complete c3a1a87b600e: Pull complete 307b97780b43: Pull complete e6bc907e1abd: Pull complete f7d60f9c5e35: Pull complete 6d95f9b81e1b: Pull complete 3fc72998ebc8: Pull complete 632905c48be3: Pull complete 29b4e1262307: Pull complete Digest: sha256:a57849f1f639b5f4e01af33fdf4b86238dead6ddaf8f95b4e658863dfcf22700 Status: Downloaded newer image quay.io/andreipope/modified-with-copy:latest for 5. List your Docker images: docker images REPOSITORY TAG IMAGE ID CREATED SIZE quay.io/andreipope/modified-with-copy latest 05b3081ac594 About an hour ago 914MB 6. Issue the following command to run the image: docker run modified-with-copy docker run -dt -p 3000:3000 quay.io/andreipope/modified-with-copy 6394d8a8b60106125a062504d3764fcd0034b06947cfe303f9be0e87b82fee88 7. Point your browser to and you should see something similar to the screenshot below: http://localhost:3000 In this tutorial, you learned how to: Use Buildah to build an image from an existing image Build an image from Scratch Build an image from a Dockerfile Use Buildah to modify an existing container Run your Buildah images with Podman and Docker Push images to a public repository We hope this blog post has been helpful and that now you know how to build container images with Buildah. Thanks for reading! About the author - Sudip is a Solution Architect with more than 15 years of working experience, and is the founder of Javelynn . He likes sharing his knowledge by regularly writing for Hackernoon , DZone , Appfleet and many more. And while he is not doing that, he must be fishing or playing chess. Previously posted at https://appfleet.com/ .