The source package usually consists of the original compressed tar file, spec file and the patches which are required to create the binary package file. If you are new to rpm package, you may first want to understand how to use rpm command to install, upgrade and remove packages on CentOS or RedHat. To build an rpm file based on the spec file that we just created, we need to use rpmbuild command.
But, the steps are exactly the same for building RPM for any other application. You just have to download the corresponding source code for the RPM that you are trying to build. In this step, we direct RPM in the build process by creating a spec file. The spec file usually consists of the following eight different sections:. Below that line, you will see the make utility which determines the list of files needs to be compiled and compiles them appropriately.
Once the SPEC file is ready, you can start building your rpm with rpm —b command. The —b option is used to perform all the phases of the build process. If you see any errors during this phase, then you need to resolve it before re-attempting again. The errors will be usually of library dependencies and you can download and install it as necessary. If the serial number is not incremented, the primary nameserver will have the correct, new information, but the secondary nameservers will never be notified of the change, and will not attempt to refresh their data of that zone.
If a firewall is blocking connections from the named service to other nameservers, the recommended practice is to change the firewall settings. Using a fixed UDP source port for DNS queries is a potential security vulnerability that could allow an attacker to conduct cache-poisoning attacks more easily. To prevent this, by default DNS sends from a random ephemeral port. Configure your firewall to allow outgoing queries from a random UDP source port.
The range to is used by default. Additional Resources. The following sources of information provide additional resources regarding BIND. Installed Documentation. BIND features a full range of installed documentation covering many different topics, each placed in its own subject directory. For each item below, replace version with the version of the bind package installed on the system:. The directory containing examples of named configuration files.
The manual page for the Internet domain name server named , containing documentation on assorted arguments that can be used to control the BIND nameserver daemon.
The manual page for the lightweight resolver daemon lwresd , containing documentation on the daemon and its usage. The manual page with a comprehensive list of options available within the named configuration file.
The manual page with a comprehensive list of options available within the rndc configuration file. Online Resources. An auxiliary directory for configuration files that are included in the main configuration file. Matches any IP address that is in use by the local system.
Matches any IP address on any network to which the local system is connected. Specifies which hosts are allowed to query the nameserver for authoritative resource records. Specifies which hosts are allowed to query the nameserver for non-authoritative data such as recursive queries.
Specifies which hosts are not allowed to query the nameserver. Specifies a working directory for the named service. Used to disable one or more empty zones from the list of default prefixes that would be used. Controls whether or not empty zones are created. Specifies a list of valid IP addresses for nameservers to which the requests should be forwarded for resolution. Specifies the behavior of the forwarders directive.
It accepts the following options: first — The server will query the nameservers listed in the forwarders directive before attempting to resolve the name on its own. Specifies the IPv4 network interface on which to listen for queries. On a DNS server that also acts as a gateway, you can use this option to answer queries originating from a single network only.
All IPv4 interfaces are used by default. Specifies the IPv6 network interface on which to listen for queries.
All IPv6 interfaces are used by default. Specifies the maximum amount of memory to be used for server caches. When the limit is reached, the server causes records to expire prematurely so that the limit is not exceeded.
In a server with multiple views, the limit applies separately to the cache of each view. The default option is 32M. It accepts the following options: yes — The server will notify all secondary nameservers. Specifies the location of the process ID file created by the named service.
Specifies whether to act as a recursive server. Specifies an alternate location for statistics files. Specifies which clients are allowed to request information about this zone. Specifies which secondary servers are allowed to request a transfer of the zone's information. Specifies which hosts are allowed to dynamically update information in their zone.
Specifies the name of the file in the named working directory that contains the zone's configuration data. Specifies from which IP addresses to request authoritative zone information.
This option is used only if the zone is defined as type slave. Related Content Image. Package software and data with self-compressed scripts. Self-compressed scrips are a quick, reliable way to distribute software or data to users without a package manager, elevated privileges, or other limitations. Posted: November 23, Author: Jose Vicente Nunez Sudoer.
How to replace Docker with Podman on a Mac, revisited. Want to use Podman on macOS? There's a new way with podman machine. Here's what you need to know. Posted: November 16, Author: Dave Meurer Red Hat. How to build a home lab to learn new Linux skills. Assigning default to the --userns-remap option creates a user and group named dockremap.
See Daemon user namespace options for details on how user namespaces work. The user namespaces kernel feature is fully supported generally available in RHEL 7. However, the specific implementation of user namespaces related to the docker service is identified as a technology preview while Red Hat locks down a few security issues associated with non-root user mounts. Add the namespace. To do this, use the grubby command as follows replacing the exact version of vmlinuz with the one on your system :.
Add a value to the user. Assign users and groups to be mapped by user namespaces. Reboot the system. After the system comes up, check that the kernel options were properly assigned and that the docker service is running with user namespaces enabled. Open a separate shell outside the container to check that the assigned user ID in this case, is used to run the containerized bash shell in the example:.
A Docker registry provides a place to store and share docker containers that are saved as images that can be shared with other people. While you can build and store container images on your local system without installing a registry, or use the Docker Hub Registry to share your images with the world, installing a private registry lets you share your images with a private group of developers or users.
This section describes how to start up a local registry, load Docker images to your local registry, and use those images to start up docker containers. To create a private Docker registry you can use the docker-distribution service. To get around this issue, you could use the yumdownloader docker-distribution command to download the package to a RHEL system, copy it to the Atomic system, install it on the Atomic system using rpm-ostree install.
You could then set up the docker-distribution service as described below. Install docker-distribution : To install the docker-distribution package you must have enabled the rhelserver-extras-rpms repository as described earlier.
They you can install the package as follows:. Enable and start the docker-distribution service : Type the following to enable, start and check the status of the docker-distribution service:. Registry firewall issues : The docker-distribution service listens on TCP port , so access to that port must be open to allow clients outside of the local system to be able to use the registry.
This applies regardless of whether you are running docker-distribution and docker on the same system or on different systems. The firewalld service is available, but disabled by default in Atomic Host. You can enable and start firewalld, then open TCP port follows:. The only Docker registry that Red Hat supports at the moment is the one at registry. If you have access to a Docker image that is stored as a tarball, you can load that image into your Docker registry from your local file system.
To pull the rhel base image from the Red Hat registry, type docker pull registry. To make sure that the image originates from the Red Hat registry, type the hostname of the registry, a slash, and the image name. The following command demonstrates this and pulls the rhel image for the Red Hat Enterprise Linux 7 release from the Red Hat registry:. The repository name rhel , when passed to the docker pull command without the name of a registry preceding it, is ambiguous and could result in the retrieval of an image that originates from an untrusted registry.
If there are multiple versions of the same image, adding a tag, such as latest to form a name such as rhel:latest , lets you choose the image more explicitly. To see the images that resulted from the above docker pull command, along with any other images on your system, type docker images :.
Here is how:. With the Docker image tarball in your current directory, you can load that tarball to the local system as follows:. To push that same image to the registry running on your localhost, tag the image with your hostname or "localhost" plus the port number of the docker-distribution service TCP port If images have been pulled or loaded into your local registry, you can use the docker command docker images to view those images. The default option to push an image or repository to the upstream Docker.
To push an image to a specific registry, identify the registry, its port number, and a tag that you designate in order to identify the image. Now that you have the docker and docker-distribution services running, with a few containers available, you can start investigating the Docker environment and looking into what makes up a container. Run docker with the version and info options to get a feel for your Docker environment.
Docker images that are now on your system whether they have been run or not can be managed in several ways. The docker run command lets you say which command to run in a container. Once a container is running, you can stop, start, and restart it. You can remove containers you no longer need in fact you probably want to. Before you run an image, it is a good idea to investigate its contents. Investigate a container image After you pull an image to your local system and before you run it, it is a good idea to investigate that image.
Tools such as openscap are being integrated with container tools to allow them to scan a container image before you run it.
In the mean time, however, you can use docker inspect to get some basic information about what an image does. Inspect an image : Run docker inspect to see what command is executed when you run the container image, as well as other information. Mount an image : Using the atomic command, mount the image to the host system to further investigate its contents. Use ls or other commands to explore the contents of the image.
You can step through the packages in the container or search for particular versions that may require updating. Unmount the image : When you are done investigating the image, you can unmount it as follows:.
In the near future, look for software scanning features, such as Openscap or Black Duck, to be available for scanning your container images. When they are, you will be able to use the atomic scan command to scan your images. When you execute a docker run command, you essentially spin up and create a new container from a Docker image. That container consists of the contents of the image, plus features based on any additional options you pass on the docker run command line.
The command you pass on the docker run command line sees the inside the container as its running environment so, by default, very little can be seen of the host system. If you want to make a directory from the host available to the container, map network ports from the container to the host, limit the amount of memory the container can use, or expand the CPU shares available to the container, you can do those things from the docker run command line.
Here are some examples of docker run command lines that enable different features. After the container runs the command, which shows the IP address If you feel that this is a container you wanted to keep around and use again, consider assigning a name to it, so you can start it again later by name.
For example, I named this container myipaddr:. Here, I set the name of the container to mybash. Although there are very few applications available inside the base RHEL image, you can add more software using the yum command. With the shell open inside the container, run the following commands:. Notice that the container is a RHEL 7. The nmap command is not included in the RHEL base image.
However, you can install it with yum as shown above, then run it within that container. To leave the container, type exit. Use docker ps -a to list the container:. You could start that container again using docker start with the -ai options.
Investigating from outside of a Docker container. The docker ps -a command shows all containers, running or stopped. See the section "Working with Docker containers" for information on starting, stopping, and removing containers that exist on your system. Investigating within a running Docker container. To investigate within a running Docker container, you can use the docker exec command. The reason for using docker exec , instead of just launching the container into a bash shell, is that you can investigate the container as it is running its intended application.
Type docker ps to make sure it is running:. Enter the container with docker exec : Use the container ID or name to open a bash shell to access the running container. The rpm -qa command lets you see the RPM packages that are included inside the container.
In other words, there is an RPM database inside of the container. Viewing memory free -m shows the available memory on the host although what the container can actually use can be limited using cgroups.
Stopping containers : To stop a running container that is not attached to a terminal session, use the stop option and the container ID or number. To see a list of containers that are still hanging around your system, run the docker ps -a command. To remove containers you no longer need, use the docker rm command, with the container ID or name as an option. So far we have grabbed some existing docker container images and worked with them in various ways. To make the process of running the exact container you want less manual, you can create a Docker image from scratch or from a container you ran that combines an existing image with some other content or settings.
Once you understand how images and containers can be created from the command line, you can try building containers in a more permanent way. Building container images from Dockerfile files is by far the preferred way to create Docker formatted containers, as compared to modifying running containers and committing them to images.
The procedure here involves creating a Dockerfile file that includes many of the features illustrated earlier:. While many features for setting up a Docker development environment for RHEL 7 are in the works, there are some issues you should be aware of as you build your own docker containers:.
Entitlements : Here are a few issues associated with Red Hat entitlements as they relate to containers:. Images : By default, docker build will use the most recent version of the base image you identify from your local cache. You may want to pull docker pull command the most recent version of an image from the remote Docker registry before you build your new image. If you want a specific instance of an image, make sure you identify the tag.
For example, just asking for the image "centos" will pull the centos:latest image. If you wanted the image for CentOS 6, you should specifically pull the centos:centos6 image.
Create project directories : On the host system where you have the docker and docker-distribution services running, create a directory for the project:. Instead, add your dig options to the. Now the dig command line became very simple and easy to read without you have to type those options every time.
Instructive article… wish you published it weeks ago when I wrote digy which is a tutorial script that simplifies, yet extends, dig. Emphasis on readability of output. Also gets WAN public IP address, checks local network status, and discovers who is behind sites: check here for the latest version.
It has some illustrative examples to get started. The output is designed for further processing by other commands. Thanks for the good article. It would be good if you write an article about dns server installation too. Very practical stuff here. There are so many ways to do tasks.
Does any one else have the same problem as myself? Even with googles own free DNS dig 8. I liked hearing that you can perform bulk DNS look-ups through a text file with dig a command I just learned about today. As much as this tutorial is nice, it does not explain what the output actually is telling someone.
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