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b284e42aef
Allow users build a rootfs using docker, this will make easy if they dont have dependencies need to pull packages from a distro. Signed-off-by: Jose Carlos Venegas Munoz <jose.carlos.venegas.munoz@intel.com>
127 lines
3.9 KiB
Markdown
127 lines
3.9 KiB
Markdown
# Building a rootfs for Kata Containers Guest OS #
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The Kata Containers `rootfs` is created using `rootfs.sh`.
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## Supported base OSs ##
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The `rootfs.sh` script builds a `rootfs` based on a particular Linux\*
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distribution. To build a `rootfs`for your chosen distribution, run:
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```
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$./rootfs.sh <distro>
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```
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To check the supported `rootfs` based OS run `$rootfs-builder/rootfs.sh
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-h`, it will show the supported values of `<distro>`
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## Adding support for new base OS ##
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The script `rootfs.sh` will it check for immediate sub-directories
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containing the following expected files structure:
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- A `bash(1)` script called `rootfs_lib.sh`
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This file must contain a function called `build_rootfs()` this function
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must receive as first argument the path where the `rootfs` will be
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populated. Path: `rootfs-builder/<distro>/rootfs_lib.sh`.
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- A `bash(1)` file `config.sh`
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This represents the specific configuration for `<distro>`. It must
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provide configuration specific variables for user to modify as needed.
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The `config.sh` file will be loaded before executing `build_rootfs()` to
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provide all the needed configuration to the function. Path:
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`rootfs-builder/<distro>/config.sh`.
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To create a directory with the expected file structure run:
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```
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make -f template/Makefile ROOTFS_BASE_NAME=my_new_awesome_rootfs
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```
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After run the command above, a new directory will be created in
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`rootfs-builder/my_new_awesome_rootfs/`. To verify it is one of the
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options to build a `rootfs` run `./rootfs.sh -h`, it will show
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`my_new_awesome` as one of the options to use it for:
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```
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./rootfs.sh <distro>
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```
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Now that a new directory structure was created is need to:
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- If needed, add configuration variables to `rootfs-builder/my_new_awesome_rootfs/config.sh`
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- Implement the stub `build_rootfs()` function from `rootfs-builder/my_new_awesome_rootfs/rootfs_lib.sh`
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### Expected `rootfs` directory content ###
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After the function `build_rootfs` is called, the script expects the
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`rootfs` directory to contain /sbin/init and /sbin/kata-agent binaries.
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### (optional) Customise the `rootfs` ###
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For development uses cases, developers may want to modify the guest OS.
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To do that it is possible to use following methods:
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- Use the environment variable `EXTRA_PKG` to provide a list of space
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separated packages to be installed.
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*Note: The package names may vary among Linux* distributions, the extra
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package names must exist in the base OS flavor you use to build the
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`rootfs`*
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Example:
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```
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EXTRA_PKG="vim emacs" ./rootfs-builder/rootfs.sh \
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-r ${PWD}/myrootfs fedora
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```
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- In `rootfs-builder/<distro>/config.sh` modify the variable `PACKAGES`.
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This are the minimal set of packages needed. The configuration file must
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use the package names from the distro was created for.
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- It is possible to customise the `rootfs` directory before create an
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image based in on it.
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## Build `rootfs` using Docker* ##
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Depending on the base OS to build the `rootfs` guest OS, it is required some
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specific programs that probably are not available or installed in the system
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that will build the guest image. For this case `rootfs.sh` can use
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a Docker\* container to build the `rootfs`. The following requirements
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must be met:
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1. Docker 1.12+ installed
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2. `runc` is configured as the default runtime
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To check if `runc` is the default runtime:
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```
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$ docker info | grep 'Default Runtime: runc'
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```
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Note:
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This requirement is specifically when using Clear Containers runtime
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see [issue](https://github.com/clearcontainers/runtime/issues/828) for
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more information.
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3. Export `USE_DOCKER` variable
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```
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$ export USE_DOCKER=true
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```
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4. Use `rootfs.sh:
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Example:
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```
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$ export USE_DOCKER=true
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$ # build guest O/S rootfs based on fedora
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$ ./rootfs-builder/rootfs.sh -r "${PWD}/fedora_rootfs" fedora
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$ # build image based rootfs created above
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$ ./image-builder/image_builder.sh "${PWD}/fedora_rootfs"
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```
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