IMPORTANT
This feature is UNSTABLE. As this feature continues to evolve, APIs may not be maintained and functionality may be changed or removed.
Enabling this feature and running runC containers in your cluster has security implications. Given runC’s integration with many powerful kernel features, it is imperative that administrators understand runC security before enabling this feature.
runC is a CLI tool for spawning and running containers according to the Open Container Initiative (OCI) specification. runC was originally spun out of the original Docker infrastructure. Together with a rootfs mountpoint that is created via squashFS images, runC enables users to bundle an application together with its preferred execution environment to be executed on a target machine. For more information about the OCI, see their website.
The Linux Container Executor (LCE) allows the YARN NodeManager to launch YARN containers to run either directly on the host machine, inside of Docker containers, and now inside of runC containers. The application requesting the resources can specify for each container how it should be executed. The LCE also provides enhanced security and is required when deploying a secure cluster. When the LCE launches a YARN container to execute in a runC container, the application can specify the runC image to be used. These runC images can be built from Docker images.
runC containers provide a custom execution environment in which the application’s code runs, isolated from the execution environment of the NodeManager and other applications. These containers can include special libraries needed by the application, and they can have different versions of native tools and libraries including Perl, Python, and Java. runC containers can even run a different flavor of Linux than what is running on the NodeManager.
runC for YARN provides both consistency (all YARN containers will have the same software environment) and isolation (no interference with whatever is installed on the physical machine).
runC support in the LCE is still evolving. To track progress and take a look at the runC design document, check out YARN-9014, the umbrella JIRA for runC support improvements.
The LCE requires that container-executor binary be owned by root:hadoop and have 6050 permissions. In order to launch runC containers, runC must be installed on all NodeManager hosts where runC containers will be launched.
The following properties should be set in yarn-site.xml:
<configuration>
<property>
<name>yarn.nodemanager.container-executor.class</name>
<value>org.apache.hadoop.yarn.server.nodemanager.LinuxContainerExecutor</value>
<description>
This is the container executor setting that ensures that all applications
are started with the LinuxContainerExecutor.
</description>
</property>
<property>
<name>yarn.nodemanager.linux-container-executor.group</name>
<value>hadoop</value>
<description>
The POSIX group of the NodeManager. It should match the setting in
"container-executor.cfg". This configuration is required for validating
the secure access of the container-executor binary.
</description>
</property>
<property>
<name>yarn.nodemanager.linux-container-executor.nonsecure-mode.limit-users</name>
<value>false</value>
<description>
Whether all applications should be run as the NodeManager process' owner.
When false, applications are launched instead as the application owner.
</description>
</property>
<property>
<name>yarn.nodemanager.runtime.linux.allowed-runtimes</name>
<value>default,runc</value>
<description>
Comma separated list of runtimes that are allowed when using
LinuxContainerExecutor. The allowed values are default, docker, runc, and
javasandbox.
</description>
</property>
<property>
<name>yarn.nodemanager.runtime.linux.type</name>
<value></value>
<description>
Optional. Sets the default container runtime to use.
</description>
</property>
<property>
<description>The runC image tag to manifest plugin
class to be used.</description>
<name>yarn.nodemanager.runtime.linux.runc.image-tag-to-manifest-plugin</name>
<value>org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.runtime.runc.ImageTagToManifestPlugin</value>
</property>
<property>
<description>The runC manifest to resources plugin class to
be used.</description>
<name>yarn.nodemanager.runtime.linux.runc.manifest-to-resources-plugin</name>
<value>org.apache.hadoop.yarn.server.nodemanager.containermanager.linux.runtime.runc.HdfsManifestToResourcesPlugin</value>
</property>
<property>
<description>The HDFS location under which the oci image manifests, layers,
and configs directories exist.</description>
<name>yarn.nodemanager.runtime.linux.runc.image-toplevel-dir</name>
<value>/runc-root</value>
</property>
<property>
<description>Target count of layer mounts that we should keep on disk
at one time.</description>
<name>yarn.nodemanager.runtime.linux.runc.layer-mounts-to-keep</name>
<value>100</value>
</property>
<property>
<description>The interval in seconds between executions of
reaping layer mounts.</description>
<name>yarn.nodemanager.runtime.linux.runc.layer-mounts-interval-secs</name>
<value>600</value>
</property>
<property>
<description>Image to be used if no other image is specified.</description>
<name>yarn.nodemanager.runtime.linux.runc.image-name</name>
<value></value>
</property>
<property>
<description>Allow or disallow privileged containers.</description>
<name>yarn.nodemanager.runtime.linux.runc.privileged-containers.allowed</name>
<value>false</value>
</property>
<property>
<description>The set of networks allowed when launching containers
using the RuncContainerRuntime.</description>
<name>yarn.nodemanager.runtime.linux.runc.allowed-container-networks</name>
<value>host,none,bridge</value>
</property>
<property>
<description>The set of runtimes allowed when launching containers
using the RuncContainerRuntime.</description>
<name>yarn.nodemanager.runtime.linux.runc.allowed-container-runtimes</name>
<value>runc</value>
</property>
<property>
<description>ACL list for users allowed to run privileged
containers.</description>
<name>yarn.nodemanager.runtime.linux.runc.privileged-containers.acl</name>
<value></value>
</property>
<property>
<description>Allow host pid namespace for runC containers.
Use with care.</description>
<name>yarn.nodemanager.runtime.linux.runc.host-pid-namespace.allowed</name>
<value>false</value>
</property>
<property>
<description>The default list of read-only mounts to be bind-mounted
into all runC containers that use RuncContainerRuntime.</description>
<name>yarn.nodemanager.runtime.linux.runc.default-ro-mounts</name>
<value></value>
</property>
<property>
<description>The default list of read-write mounts to be bind-mounted
into all runC containers that use RuncContainerRuntime.</description>
<name>yarn.nodemanager.runtime.linux.runc.default-rw-mounts</name>
<value></value>
</property>
<property>
<description>Path to the seccomp profile to use with runC
containers</description>
<name>yarn.nodemanager.runtime.linux.runc.seccomp-profile</name>
<value></value>
</property>
<property>
<description>The HDFS location where the runC image tag to hash
file exists.</description>
<name>yarn.nodemanager.runtime.linux.runc.image-tag-to-manifest-plugin.hdfs-hash-file</name>
<value>/runc-root/image-tag-to-hash</value>
</property>
<property>
<description>The local file system location where the runC image tag
to hash file exists.</description>
<name>yarn.nodemanager.runtime.linux.runc.image-tag-to-manifest-plugin.local-hash-file</name>
<value></value>
</property>
<property>
<description>The interval in seconds between refreshing the hdfs image tag
to hash cache.</description>
<name>yarn.nodemanager.runtime.linux.runc.image-tag-to-manifest-plugin.cache-refresh-interval-secs</name>
<value>60</value>
</property>
<property>
<description>The number of manifests to cache in the image tag
to hash cache.</description>
<name>yarn.nodemanager.runtime.linux.runc.image-tag-to-manifest-plugin.num-manifests-to-cache</name>
<value>10</value>
</property>
<property>
<description>The timeout value in seconds for the values in
the stat cache.</description>
<name>yarn.nodemanager.runtime.linux.runc.hdfs-manifest-to-resources-plugin.stat-cache-timeout-interval-secs</name>
<value>360</value>
</property>
<property>
<description>The size of the stat cache which stores stats of the
layers and config.</description>
<name>yarn.nodemanager.runtime.linux.runc.hdfs-manifest-to-resources-plugin.stat-cache-size</name>
<value>500</value>
</property>
</configuration>
In addition, a container-executor.cfg file must exist and contain settings for the container executor. The file must be owned by root with permissions 0400. The format of the file is the standard Java properties file format, for example
`key=value`
The following properties are required to enable runC support:
| Configuration Name | Description |
|---|---|
yarn.nodemanager.linux-container-executor.group |
The Unix group of the NodeManager. It should match the yarn.nodemanager.linux-container-executor.group in the yarn-site.xml file. |
The container-executor.cfg must contain a section to determine the capabilities that containers are allowed. It contains the following properties:
| Configuration Name | Description |
|---|---|
module.enabled |
Must be “true” or “false” to enable or disable launching runC containers respectively. Default value is 0. |
runc.binary |
The binary used to launch runC containers. /usr/bin/runc by default. |
runc.run-root |
The directory where all runtime mounts and overlay mounts will be placed. |
runc.allowed.ro-mounts |
Comma separated directories that containers are allowed to mount in read-only mode. By default, no directories are allowed to mounted. |
runc.allowed.rw-mounts |
Comma separated directories that containers are allowed to mount in read-write mode. By default, no directories are allowed to mounted. |
Please note that if you wish to run runC containers that require access to the YARN local directories, you must add them to the runc.allowed.rw-mounts list.
In addition, containers are not permitted to mount any parent of the container-executor.cfg directory in read-write mode.
The following properties are optional:
| Configuration Name | Description |
|---|---|
min.user.id |
The minimum UID that is allowed to launch applications. The default is no minimum |
banned.users |
A comma-separated list of usernames who should not be allowed to launch applications. The default setting is: yarn, mapred, hdfs, and bin. |
allowed.system.users |
A comma-separated list of usernames who should be allowed to launch applications even if their UIDs are below the configured minimum. If a user appears in allowed.system.users and banned.users, the user will be considered banned. |
feature.tc.enabled |
Must be “true” or “false”. “false” means traffic control commands are disabled. “true” means traffic control commands are allowed. |
feature.yarn.sysfs.enabled |
Must be “true” or “false”. See YARN sysfs support for detail. The default setting is disabled. |
Part of a container-executor.cfg which allows runC containers to be launched is below:
yarn.nodemanager.linux-container-executor.group=yarn [runc] module.enabled=true runc.binary=/usr/bin/runc runc.run-root=/run/yarn-container-executor runc.allowed.ro-mounts=/sys/fs/cgroup runc.allowed.rw-mounts=/var/hadoop/yarn/local-dir,/var/hadoop/yarn/log-dir
runC containers are run inside of images that are derived from Docker images. The docker images are transformed into a set of squashFS file images and uploaded into HDFS. In order to work with YARN, there are a few requirements for these Docker images.
The runC container will be explicitly launched with the application owner as the container user. If the application owner is not a valid user in the Docker image, the application will fail. The container user is specified by the user’s UID. If the user’s UID is different between the NodeManager host and the Docker image, the container may be launched as the wrong user or may fail to launch because the UID does not exist. See User Management in runC Container section for more details.
The Docker image must have whatever is expected by the application in order to execute. In the case of Hadoop (MapReduce or Spark), the Docker image must contain the JRE and Hadoop libraries and have the necessary environment variables set: JAVA_HOME, HADOOP_COMMON_PATH, HADOOP_HDFS_HOME, HADOOP_MAPRED_HOME, HADOOP_YARN_HOME, and HADOOP_CONF_DIR. Note that the Java and Hadoop component versions available in the Docker image must be compatible with what’s installed on the cluster and in any other Docker images being used for other tasks of the same job. Otherwise the Hadoop components started in the runC container may be unable to communicate with external Hadoop components.
/bin/bash must be available inside the image. This is generally true, however, tiny Docker images (eg. ones which use busybox for shell commands) might not have bash installed. In this case, the following error is displayed:
Container id: container_1561638268473_0015_01_000002 Exit code: 7 Exception message: Launch container failed Shell error output: /usr/bin/docker-current: Error response from daemon: oci runtime error: container_linux.go:235: starting container process caused "exec: \"bash\": executable file not found in $PATH". Shell output: main : command provided 4
find command must also be available inside the image. Not having find causes this error:
Container exited with a non-zero exit code 127. Error file: prelaunch.err. Last 4096 bytes of prelaunch.err : /tmp/hadoop-systest/nm-local-dir/usercache/hadoopuser/appcache/application_1561638268473_0017/container_1561638268473_0017_01_000002/launch_container.sh: line 44: find: command not found
If a Docker image has an entry point set, the entry point will be executed with the launch command of the container as its arguments.
The runC images that are derived from Docker images are localized onto the hosts where the runC containers will execute just like any other localized resource would be. Both MapReduce and Spark assume that tasks which take more that 10 minutes to report progress have stalled, so specifying a large image may cause the application to fail if the localization takes too long.
Every Docker image is comprised of 3 things: - A set of layers that create the file system. - A config file that holds information relative to the environment of the image. - A manifest that describes what layers and config are needed for that image.
Together, these 3 pieces combine to create an Open Container Initiative (OCI) compliant image. runC runs on top of OCI-compliant containers, but with a small twist. Each layer that the runC runtime uses is compressed into squashFS file system. The squashFS layers, along with the config, and manifest are uploaded to HDFS along with an image-tag-to-hash mapping file that describes the mapping between image tags and the manifest associated with that image. Getting this all setup is a complicated and tedious process. There is a patch on YARN-9564 that contains an unofficial Python script named docker-to-squash.py to help out with the conversion process. This tool will take in a Docker image as input, convert all of its layers into squashFS file systems, and upload the squashFS layers, config, and manifest to HDFS underneath the runc-root. It will also create or update the image-tag-to-hash mapping file. Below is an example invocation of the script to upload an image named centos:latest to HDFS with the runC image name centos
[user@foobar sbin]$ pwd
/home/user/hadoop/hadoop-dist/target/hadoop-3.3.0-SNAPSHOT/sbin
[user@foobar sbin]$ ls
distribute-exclude.sh hadoop-daemons.sh refresh-namenodes.sh start-dfs.cmd start-yarn.sh stop-dfs.cmd stop-yarn.sh
docker_to_squash.py httpfs.sh start-all.cmd start-dfs.sh stop-all.cmd stop-dfs.sh workers.sh
FederationStateStore kms.sh start-all.sh start-secure-dns.sh stop-all.sh stop-secure-dns.sh yarn-daemon.sh
hadoop-daemon.sh mr-jobhistory-daemon.sh start-balancer.sh start-yarn.cmd stop-balancer.sh stop-yarn.cmd yarn-daemons.sh
[user@foobar sbin]$ hadoop fs -ls /
Found 3 items
drwxrwx--- - user supergroup 0 2019-08-07 19:35 /home
drwx------ - user supergroup 0 2019-08-07 19:35 /tmp
drwx------ - user supergroup 0 2019-08-07 19:35 /user
[user@foobar sbin]$ ./docker_to_squash.py --working-dir /tmp --log=DEBUG pull-build-push-update centos:latest,centos
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'version']
DEBUG: command: ['skopeo', '-v']
DEBUG: command: ['mksquashfs', '-version']
DEBUG: args: Namespace(LOG_LEVEL='DEBUG', check_magic_file=False, force=False, func=<function pull_build_push_update at 0x7fe6974cd9b0>, hadoop_prefix='/hadoop-2.8.6-SNAPSHOT', hdfs_root='/runc-root', image_tag_to_hash='image-tag-to-hash', images_and_tags=['centos:latest,centos'], magic_file='etc/dockerfile-version', pull_format='docker', replication=1, skopeo_format='dir', sub_command='pull-build-push-update', working_dir='/tmp')
DEBUG: extra: []
DEBUG: image-tag-to-hash: image-tag-to-hash
DEBUG: LOG_LEVEL: DEBUG
DEBUG: HADOOP_BIN_DIR: /hadoop-2.8.6-SNAPSHOT/bin
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root']
ls: `/runc-root': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-mkdir', '/runc-root']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '755', '/runc-root']
DEBUG: Setting up squashfs dirs: ['/runc-root/layers', '/runc-root/config', '/runc-root/manifests']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/layers']
ls: `/runc-root/layers': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-mkdir', '/runc-root/layers']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/layers']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '755', '/runc-root/layers']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/config']
ls: `/runc-root/config': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-mkdir', '/runc-root/config']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/config']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '755', '/runc-root/config']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/manifests']
ls: `/runc-root/manifests': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-mkdir', '/runc-root/manifests']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/manifests']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '755', '/runc-root/manifests']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/image-tag-to-hash']
ls: `/runc-root/image-tag-to-hash': No such file or directory
INFO: Working on image centos:latest with tags ['centos']
DEBUG: command: ['skopeo', 'inspect', '--raw', 'docker://centos:latest']
DEBUG: skopeo inspect --raw returned a list of manifests
DEBUG: amd64 manifest sha is: sha256:ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66
DEBUG: command: ['skopeo', 'inspect', '--raw', u'docker://centos@sha256:ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66']
INFO: manifest: {u'layers': [{u'mediaType': u'application/vnd.docker.image.rootfs.diff.tar.gzip', u'digest': u'sha256:8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df', u'size': 75403831}], u'schemaVersion': 2, u'config': {u'mediaType': u'application/vnd.docker.container.image.v1+json', u'digest': u'sha256:9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1', u'size': 2182}, u'mediaType': u'application/vnd.docker.distribution.manifest.v2+json'}
INFO: manifest: {u'layers': [{u'mediaType': u'application/vnd.docker.image.rootfs.diff.tar.gzip', u'digest': u'sha256:8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df', u'size': 75403831}], u'schemaVersion': 2, u'config': {u'mediaType': u'application/vnd.docker.container.image.v1+json', u'digest': u'sha256:9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1', u'size': 2182}, u'mediaType': u'application/vnd.docker.distribution.manifest.v2+json'}
DEBUG: Layers: [u'8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df']
DEBUG: Config: 9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1
DEBUG: hash_to_tags is null. Not removing tag centos
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66']
ls: `/runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', u'/runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1']
ls: `/runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', u'/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh']
ls: `/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh': No such file or directory
DEBUG: skopeo_dir: /tmp/docker-to-squash/centos:latest
INFO: Pulling image: centos:latest
DEBUG: command: ['skopeo', 'copy', 'docker://centos:latest', 'dir:/tmp/docker-to-squash/centos:latest']
INFO: Squashifying and uploading layer: 8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', u'/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh']
ls: `/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh': No such file or directory
DEBUG: command: ['sudo', 'tar', '-C', u'/tmp/docker-to-squash/expand_archive_8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df', '--xattrs', "--xattrs-include='*'", '-xzf', u'/tmp/docker-to-squash/centos:latest/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df']
DEBUG: command: ['sudo', 'find', u'/tmp/docker-to-squash/expand_archive_8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df', '-name', '.wh.*']
DEBUG: command: ['sudo', 'mksquashfs', u'/tmp/docker-to-squash/expand_archive_8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df', u'/tmp/docker-to-squash/centos:latest/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh']
DEBUG: command: ['sudo', 'rm', '-rf', u'/tmp/docker-to-squash/expand_archive_8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', u'/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh']
ls: `/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-put', u'/tmp/docker-to-squash/centos:latest/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh', u'/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-setrep', '1', u'/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '444', u'/runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh']
INFO: Uploaded file /runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh with replication 1 and permissions 444
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', u'/runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1']
ls: `/runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-put', u'/tmp/docker-to-squash/centos:latest/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1', u'/runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-setrep', '1', u'/runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '444', u'/runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1']
INFO: Uploaded file /runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1 with replication 1 and permissions 444
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-ls', '/runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66']
ls: `/runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66': No such file or directory
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-put', '/tmp/docker-to-squash/centos:latest/manifest.json', '/runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-setrep', '1', '/runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '444', '/runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66']
INFO: Uploaded file /runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66 with replication 1 and permissions 444
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-put', '-f', '/tmp/docker-to-squash/image-tag-to-hash', '/runc-root/image-tag-to-hash']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-setrep', '1', '/runc-root/image-tag-to-hash']
DEBUG: command: ['/hadoop-2.8.6-SNAPSHOT/bin/hadoop', 'fs', '-chmod', '444', '/runc-root/image-tag-to-hash']
DEBUG: command: ['sudo', 'rm', '-rf', '/tmp/docker-to-squash']
[user@foobar sbin]$ hadoop fs -ls /
Found 4 items
drwxrwx--- - user supergroup 0 2019-08-07 19:35 /home
drwxr-xr-x - user supergroup 0 2019-08-08 22:38 /runc-root
drwx------ - user supergroup 0 2019-08-07 19:35 /tmp
drwx------ - user supergroup 0 2019-08-07 19:35 /user
[user@foobar sbin]$ hadoop fs -ls /runc-root/*
Found 1 items
-r--r--r-- 1 user supergroup 2182 2019-08-08 22:38 /runc-root/config/9f38484d220fa527b1fb19747638497179500a1bed8bf0498eb788229229e6e1
-r--r--r-- 1 user supergroup 86 2019-08-08 22:38 /runc-root/image-tag-to-hash
Found 1 items
-r--r--r-- 1 user supergroup 73625600 2019-08-08 22:38 /runc-root/layers/8ba884070f611d31cb2c42eddb691319dc9facf5e0ec67672fcfa135181ab3df.sqsh
Found 1 items
-r--r--r-- 1 user supergroup 529 2019-08-08 22:38 /runc-root/manifests/ca58fe458b8d94bc6e3072f1cfbd334855858e05e1fd633aa07cf7f82b048e66
Before attempting to launch a runC container, make sure that the LCE configuration is working for applications requesting regular YARN containers. If after enabling the LCE one or more NodeManagers fail to start, the cause is most likely that the ownership and/or permissions on the container-executor binary are incorrect. Check the logs to confirm.
In order to run an application in a runC container, set the following environment variables in the application’s environment:
| Environment Variable Name | Description |
|---|---|
YARN_CONTAINER_RUNTIME_TYPE |
Determines whether an application will be launched in a runC container. If the value is “runc”, the application will be launched in a runC container. Otherwise a regular process tree container will be used. |
YARN_CONTAINER_RUNTIME_RUNC_IMAGE |
Names which image will be used to launch the runC container. |
YARN_CONTAINER_RUNTIME_RUNC_CONTAINER_HOSTNAME |
Sets the hostname to be used by the runC container. |
YARN_CONTAINER_RUNTIME_RUNC_MOUNTS |
Adds additional volume mounts to the runC container. The value of the environment variable should be a comma-separated list of mounts. All such mounts must be given as “source:dest:mode” and the mode must be “ro” (read-only) or “rw” (read-write) to specify the type of access being requested. If neither is specified, read-write will be assumed. The requested mounts will be validated by container-executor based on the values set in container-executor.cfg for runc.allowed.ro-mounts and runc.allowed.rw-mounts. |
The first two are required. The remainder can be set as needed. While controlling the container type through environment variables is somewhat less than ideal, it allows applications with no awareness of YARN’s runC support (such as MapReduce and Spark) to nonetheless take advantage of it through their support for configuring the application environment.
Note The runtime will not work if you mount anything onto /tmp or /var/tmp in the container.
Once an application has been submitted to be launched in a runC container, the application will behave exactly as any other YARN application. Logs will be aggregated and stored in the relevant history server. The application life cycle will be the same as for a non-runC application.
WARNING Care should be taken when enabling this feature. Enabling access to directories such as, but not limited to, /, /etc, /run, or /home is not advisable and can result in containers negatively impacting the host or leaking sensitive information. WARNING
Files and directories from the host are commonly needed within the runC containers, which runC provides through mounts into the container. Examples include localized resources, Apache Hadoop binaries, and sockets.
In order to mount anything into the container, the following must be configured.
runc.allowed.ro-mounts and runc.allowed.rw-mounts to the list of parent directories that are allowed to be mounted.The administrator supplied whitelist is defined as a comma separated list of directories that are allowed to be mounted into containers. The source directory supplied by the user must either match or be a child of the specified directory.
The user supplied mount list is defined as a comma separated list in the form source:destination or source:destination:mode. The source is the file or directory on the host. The destination is the path within the container where the source will be bind mounted. The mode defines the mode the user expects for the mount, which can be ro (read-only) or rw (read-write). If not specified, rw is assumed. The mode may also include a bind propagation option (shared, rshared, slave, rslave, private, or rprivate). In that case, the mode should be of the form option, rw+option, or ro+option.
The following example outlines how to use this feature to mount the commonly needed /sys/fs/cgroup directory into the container running on YARN.
The administrator sets runc.allowed.ro-mounts in container-executor.cfg to “/sys/fs/cgroup”. Applications can now request that “/sys/fs/cgroup” be mounted from the host into the container in read-only mode.
The Nodemanager has the option to setup a default list of read-only or read-write mounts to be added to the container via yarn.nodemanager.runtime.linux.runc.default-ro-mount" and yarn.nodemanager.runtime.linux.runc.default-rw-mounts in yarn-site.xml. In this example, yarn.nodemanager.runtime.linux.runc.default-ro-mounts would be set to /sys/fs/cgroup:/sys/fs/cgroup.
YARN’s runC container support launches container processes using the uid:gid identity of the user, as defined on the NodeManager host. User and group name mismatches between the NodeManager host and container can lead to permission issues, failed container launches, or even security holes. Centralizing user and group management for both hosts and containers greatly reduces these risks. When running containerized applications on YARN, it is necessary to understand which uid:gid pair will be used to launch the container’s process.
As an example of what is meant by uid:gid pair, consider the following. By default, in non-secure mode, YARN will launch processes as the user nobody (see the table at the bottom of Using Cgroups with YARN for how the run as user is determined in non-secure mode). On CentOS based systems, the nobody user’s uid is 99 and the nobody group is 99. As a result, YARN will invoke runC with uid 99 and gid 99. If the nobody user does not have the uid 99 in the container, the launch may fail or have unexpected results.
There are many ways to address user and group management. runC, by default, will authenticate users against /etc/passwd (and /etc/shadow) within the container. Using the default /etc/passwd supplied in the runC image is unlikely to contain the appropriate user entries and will result in launch failures. It is highly recommended to centralize user and group management. Several approaches to user and group management are outlined below.
The most basic approach to managing user and groups is to modify the user and group within the runC image. This approach is only viable in non-secure mode where all container processes will be launched as a single known user, for instance nobody. In this case, the only requirement is that the uid:gid pair of the nobody user and group must match between the host and container. On a CentOS based system, this means that the nobody user in the container needs the UID 99 and the nobody group in the container needs GID 99.
One approach to change the UID and GID is by leveraging usermod and groupmod. The following sets the correct UID and GID for the nobody user/group.
usermod -u 99 nobody groupmod -g 99 nobody
This approach is not recommended beyond testing given the inflexibility to add users.
When organizations already have automation in place to create local users on each system, it may be appropriate to bind mount /etc/passwd and /etc/group into the container as an alternative to modifying the container image directly. To enable the ability to bind mount /etc/passwd and /etc/group, update runc.allowed.ro-mounts in container-executor.cfg to include those paths. For this to work on runC, “yarn.nodemanager.runtime.linux.runc.default-ro-mounts” will need to include /etc/passwd:/etc/passwd:ro and /etc/group:/etc/group:ro.
There are several challenges with this bind mount approach that need to be considered.
This approach is not recommended beyond testing given the inflexibility to modify running containers.
An alternative approach that allows for centrally managing users and groups is SSSD. System Security Services Daemon (SSSD) provides access to different identity and authentication providers, such as LDAP or Active Directory.
The traditional schema for Linux authentication is as follows:
application -> libpam -> pam_authenticate -> pam_unix.so -> /etc/passwd
If we use SSSD for user lookup, it becomes:
application -> libpam -> pam_authenticate -> pam_sss.so -> SSSD -> pam_unix.so -> /etc/passwd
We can bind-mount the UNIX sockets SSSD communicates over into the container. This will allow the SSSD client side libraries to authenticate against the SSSD running on the host. As a result, user information does not need to exist in /etc/passwd of the docker image and will instead be serviced by SSSD.
Step by step configuration for host and container:
# yum -y install sssd-common sssd-proxy
# cat /etc/pam.d/sss_proxy auth required pam_unix.so account required pam_unix.so password required pam_unix.so session required pam_unix.so
# cat /etc/sssd/sssd/conf [sssd] services = nss,pam config_file_version = 2 domains = proxy [nss] [pam] [domain/proxy] id_provider = proxy proxy_lib_name = files proxy_pam_target = sss_proxy
# systemctl start sssd
# getent passwd -s sss localuser
It’s important to bind-mount the /var/lib/sss/pipes directory from the host to the container since SSSD UNIX sockets are located there.
-v /var/lib/sss/pipes:/var/lib/sss/pipes:rw
All the steps below should be executed on the container itself.
Install only the sss client libraries
# yum -y install sssd-client
make sure sss is configured for passwd and group databases in
/etc/nsswitch.conf
configure the PAM service that the application uses to call into SSSD
# cat /etc/pam.d/system-auth #%PAM-1.0 # This file is auto-generated. # User changes will be destroyed the next time authconfig is run. auth required pam_env.so auth sufficient pam_unix.so try_first_pass nullok auth sufficient pam_sss.so forward_pass auth required pam_deny.so account required pam_unix.so account [default=bad success=ok user_unknown=ignore] pam_sss.so account required pam_permit.so password requisite pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type= password sufficient pam_unix.so try_first_pass use_authtok nullok sha512 shadow password sufficient pam_sss.so use_authtok password required pam_deny.so session optional pam_keyinit.so revoke session required pam_limits.so -session optional pam_systemd.so session [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid session required pam_unix.so session optional pam_sss.so
Save the docker image and use the docker image as base image for your applications.
test the docker image launched in YARN environment.
$ id uid=5000(localuser) gid=5000(localuser) groups=5000(localuser),1337(hadoop)
This example assumes that Hadoop is installed to /usr/local/hadoop.
You will also need to squashify a Docker image and upload it to HDFS before you can run with that image. See Transforming a Docker Image into a runC Image for instructions on how to transform a Docker image into a image that runC can use. For this example, we will assume that you have done with that an image named hadoop-image.
Additionally, runc.allowed.ro-mounts in container-executor.cfg has been updated to include the directories: /usr/local/hadoop,/etc/passwd,/etc/group.
To submit the pi job to run in runC containers, run the following commands:
HADOOP_HOME=/usr/local/hadoop
YARN_EXAMPLES_JAR=$HADOOP_HOME/share/hadoop/mapreduce/hadoop-mapreduce-examples-*.jar
MOUNTS="$HADOOP_HOME:$HADOOP_HOME:ro,/etc/passwd:/etc/passwd:ro,/etc/group:/etc/group:ro"
IMAGE_ID="hadoop-image"
export YARN_CONTAINER_RUNTIME_TYPE=runc
export YARN_CONTAINER_RUNTIME_RUNC_IMAGE=$IMAGE_ID
export YARN_CONTAINER_RUNTIME_RUNC_MOUNTS=$MOUNTS
yarn jar $YARN_EXAMPLES_JAR pi \
-Dmapreduce.map.env.YARN_CONTAINER_RUNTIME_TYPE=runc \
-Dmapreduce.map.env.YARN_CONTAINER_RUNTIME_RUNC_MOUNTS=$MOUNTS \
-Dmapreduce.map.env.YARN_CONTAINER_RUNTIME_RUNC_IMAGE=$IMAGE_ID \
-Dmapreduce.reduce.env.YARN_CONTAINER_RUNTIME_TYPE=runc \
-Dmapreduce.reduce.env.YARN_CONTAINER_RUNTIME_RUNC_MOUNTS=$MOUNTS \
-Dmapreduce.reduce.env.YARN_CONTAINER_RUNTIME_RUNC_IMAGE=$IMAGE_ID \
1 40000
Note that the application master, map tasks, and reduce tasks are configured independently. In this example, we are using the hadoop-image image for all three.
This example assumes that Hadoop is installed to /usr/local/hadoop and Spark is installed to /usr/local/spark.
You will also need to squashify a Docker image and upload it to HDFS before you can run with that image. See Transforming a Docker Image into a runC Image for instructions on how to transform a Docker image into a image that runC can use. For this example, we will assume that you have done with that an image named hadoop-image.
Additionally, runc.allowed.ro-mounts in container-executor.cfg has been updated to include the directories: /usr/local/hadoop,/etc/passwd,/etc/group.
To run a Spark shell in runC containers, run the following command:
HADOOP_HOME=/usr/local/hadoop
SPARK_HOME=/usr/local/spark
MOUNTS="$HADOOP_HOME:$HADOOP_HOME:ro,/etc/passwd:/etc/passwd:ro,/etc/group:/etc/group:ro"
IMAGE_ID="hadoop-image"
$SPARK_HOME/bin/spark-shell --master yarn \
--conf spark.yarn.appMasterEnv.YARN_CONTAINER_RUNTIME_TYPE=runc \
--conf spark.yarn.appMasterEnv.YARN_CONTAINER_RUNTIME_RUNC_IMAGE=$IMAGE_ID \
--conf spark.yarn.appMasterEnv.YARN_CONTAINER_RUNTIME_RUNC_MOUNTS=$MOUNTS \
--conf spark.executorEnv.YARN_CONTAINER_RUNTIME_TYPE=runc \
--conf spark.executorEnv.YARN_CONTAINER_RUNTIME_RUNC_IMAGE=$IMAGE_ID \
--conf spark.executorEnv.YARN_CONTAINER_RUNTIME_RUNC_MOUNTS=$MOUNTS
Note that the application master and executors are configured independently. In this example, we are using the hadoop-image image for both.