config.md
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# Container Configuration file
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The container's top-level directory MUST contain a configuration file called `config.json`.
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The canonical schema is defined in this document, but there is a JSON Schema in [`schema/config-schema.json`](schema/config-schema.json) and Go bindings in [`specs-go/config.go`](specs-go/config.go).
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The configuration file contains metadata necessary to implement standard operations against the container.
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This includes the process to run, environment variables to inject, sandboxing features to use, etc.
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Below is a detailed description of each field defined in the configuration format.
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## Specification version
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* **`ociVersion`** (string, required) MUST be in [SemVer v2.0.0](http://semver.org/spec/v2.0.0.html) format and specifies the version of the Open Container Runtime Specification with which the bundle complies.
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The Open Container Runtime Specification follows semantic versioning and retains forward and backward compatibility within major versions.
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For example, if an implementation is compliant with version 1.0.1 of the spec, it is compatible with the complete 1.x series.
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### Example
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"ociVersion": "0.1.0"
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```
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## Root Configuration
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**`root`** (object, required) configures the container's root filesystem.
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* **`path`** (string, required) Specifies the path to the root filesystem for the container.
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A directory MUST exist at the path declared by the field.
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* **`readonly`** (bool, optional) If true then the root filesystem MUST be read-only inside the container, defaults to false.
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### Example
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"root": {
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"path": "rootfs",
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"readonly": true
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}
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```
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## Mounts
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**`mounts`** (array, optional) configures additional mounts (on top of [`root`](#root-configuration)).
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The runtime MUST mount entries in the listed order.
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The parameters are similar to the ones in [the Linux mount system call](http://man7.org/linux/man-pages/man2/mount.2.html).
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* **`destination`** (string, required) Destination of mount point: path inside container.
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For the Windows operating system, one mount destination MUST NOT be nested within another mount (e.g., c:\\foo and c:\\foo\\bar).
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* **`type`** (string, required) The filesystem type of the filesystem to be mounted.
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Linux: *filesystemtype* argument supported by the kernel are listed in */proc/filesystems* (e.g., "minix", "ext2", "ext3", "jfs", "xfs", "reiserfs", "msdos", "proc", "nfs", "iso9660").
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Windows: ntfs.
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* **`source`** (string, required) A device name, but can also be a directory name or a dummy.
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Windows: the volume name that is the target of the mount point, \\?\Volume\{GUID}\ (on Windows source is called target).
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* **`options`** (list of strings, optional) Mount options of the filesystem to be used.
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Linux: [supported][mount.8-filesystem-independent] [options][mount.8-filesystem-specific] are listed in [mount(8)][mount.8].
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### Example (Linux)
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```json
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"mounts": [
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{
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"destination": "/tmp",
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"type": "tmpfs",
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"source": "tmpfs",
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"options": ["nosuid","strictatime","mode=755","size=65536k"]
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"destination": "/data",
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"type": "bind",
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"source": "/volumes/testing",
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"options": ["rbind","rw"]
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}
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]
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```
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### Example (Windows)
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```json
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"mounts": [
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"myfancymountpoint": {
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"destination": "C:\\Users\\crosbymichael\\My Fancy Mount Point\\",
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"type": "ntfs",
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"source": "\\\\?\\Volume\\{2eca078d-5cbc-43d3-aff8-7e8511f60d0e}\\",
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"options": []
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}
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]
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```
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See links for details about [mountvol](http://ss64.com/nt/mountvol.html) and [SetVolumeMountPoint](https://msdn.microsoft.com/en-us/library/windows/desktop/aa365561(v=vs.85).aspx) in Windows.
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## Process configuration
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**`process`** (object, required) configures the container process.
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* **`terminal`** (bool, optional) specifies whether you want a terminal attached to that process, defaults to false.
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* **`cwd`** (string, required) is the working directory that will be set for the executable.
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This value MUST be an absolute path.
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* **`env`** (array of strings, optional) contains a list of variables that will be set in the process's environment prior to execution.
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Elements in the array are specified as Strings in the form "KEY=value".
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The left hand side MUST consist solely of letters, digits, and underscores `_` as outlined in [IEEE Std 1003.1-2001](http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html).
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* **`args`** (array of strings, required) executable to launch and any flags as an array.
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The executable is the first element and MUST be available at the given path inside of the rootfs.
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If the executable path is not an absolute path then the search $PATH is interpreted to find the executable.
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For Linux-based systems the process structure supports the following process specific fields:
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* **`capabilities`** (array of strings, optional) capabilities is an array that specifies Linux capabilities that can be provided to the process inside the container.
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Valid values are the strings for capabilities defined in [the man page](http://man7.org/linux/man-pages/man7/capabilities.7.html)
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* **`rlimits`** (array of rlimits, optional) rlimits is an array of rlimits that allows setting resource limits for a process inside the container.
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The kernel enforces the `soft` limit for a resource while the `hard` limit acts as a ceiling for that value that could be set by an unprivileged process.
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Valid values for the 'type' field are the resources defined in [the man page](http://man7.org/linux/man-pages/man2/setrlimit.2.html).
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* **`apparmorProfile`** (string, optional) apparmor profile specifies the name of the apparmor profile that will be used for the container.
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For more information about Apparmor, see [Apparmor documentation](https://wiki.ubuntu.com/AppArmor)
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* **`selinuxLabel`** (string, optional) SELinux process label specifies the label with which the processes in a container are run.
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For more information about SELinux, see [Selinux documentation](http://selinuxproject.org/page/Main_Page)
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* **`noNewPrivileges`** (bool, optional) setting `noNewPrivileges` to true prevents the processes in the container from gaining additional privileges.
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[The kernel doc](https://www.kernel.org/doc/Documentation/prctl/no_new_privs.txt) has more information on how this is achieved using a prctl system call.
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### User
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The user for the process is a platform-specific structure that allows specific control over which user the process runs as.
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#### Linux and Solaris User
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For Linux and Solaris based systems the user structure has the following fields:
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* **`uid`** (int, required) specifies the user ID in the [container namespace][container-namespace].
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* **`gid`** (int, required) specifies the group ID in the [container namespace][container-namespace].
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* **`additionalGids`** (array of ints, optional) specifies additional group IDs (in the [container namespace][container-namespace]) to be added to the process.
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_Note: symbolic name for uid and gid, such as uname and gname respectively, are left to upper levels to derive (i.e. `/etc/passwd` parsing, NSS, etc)_
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_Note: For Solaris, uid and gid specify the uid and gid of the process inside the container and need not be same as in the host._
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### Example (Linux)
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"process": {
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"terminal": true,
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"user": {
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"uid": 1,
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"gid": 1,
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"additionalGids": [5, 6]
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"env": [
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"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
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"TERM=xterm"
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],
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"cwd": "/root",
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"args": [
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"sh"
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"apparmorProfile": "acme_secure_profile",
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"selinuxLabel": "system_u:system_r:svirt_lxc_net_t:s0:c124,c675",
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"noNewPrivileges": true,
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"capabilities": [
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"CAP_AUDIT_WRITE",
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"CAP_KILL",
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"CAP_NET_BIND_SERVICE"
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],
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"rlimits": [
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{
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"type": "RLIMIT_NOFILE",
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"hard": 1024,
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"soft": 1024
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}
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```
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### Example (Solaris)
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```json
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"process": {
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"terminal": true,
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"user": {
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"uid": 1,
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"gid": 1,
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"additionalGids": [2, 8]
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},
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"env": [
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"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
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"TERM=xterm"
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],
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"cwd": "/root",
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"args": [
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"/usr/bin/bash"
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],
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}
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```
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## Hostname
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* **`hostname`** (string, optional) configures the container's hostname as seen by processes running inside the container.
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On Linux, you can only set this if your bundle creates a new [UTS namespace][uts-namespace].
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### Example
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"hostname": "mrsdalloway"
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```
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**`platform`** specifies the configuration's target platform.
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* **`os`** (string, required) specifies the operating system family this image targets.
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The runtime MUST generate an error if it does not support the configured **`os`**.
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Bundles SHOULD use, and runtimes SHOULD understand, **`os`** entries listed in the Go Language document for [`$GOOS`][go-environment].
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If an operating system is not included in the `$GOOS` documentation, it SHOULD be submitted to this specification for standardization.
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* **`arch`** (string, required) specifies the instruction set for which the binaries in the image have been compiled.
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The runtime MUST generate an error if it does not support the configured **`arch`**.
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Values for **`arch`** SHOULD use, and runtimes SHOULD understand, **`arch`** entries listed in the Go Language document for [`$GOARCH`][go-environment].
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If an architecture is not included in the `$GOARCH` documentation, it SHOULD be submitted to this specification for standardization.
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### Example
217
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"platform": {
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"os": "linux",
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"arch": "amd64"
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}
223
```
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## Platform-specific configuration
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[**`platform.os`**](#platform) is used to lookup further platform-specific configuration.
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* **`linux`** (object, optional) [Linux-specific configuration](config-linux.md).
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This SHOULD only be set if **`platform.os`** is `linux`.
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* **`solaris`** (object, optional) [Solaris-specific configuration](config-solaris.md).
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This SHOULD only be set if **`platform.os`** is `solaris`.
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### Example (Linux)
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```json
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{
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"platform": {
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"os": "linux",
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"arch": "amd64"
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},
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"linux": {
243
"namespaces": [
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{
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"type": "pid"
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}
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]
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}
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}
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```
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## Hooks
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**`hooks`** (object, optional) configures callbacks for container lifecycle events.
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Lifecycle hooks allow custom events for different points in a container's runtime.
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Presently there are `Prestart`, `Poststart` and `Poststop`.
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* [`Prestart`](#prestart) is a list of hooks to be run before the container process is executed
259
* [`Poststart`](#poststart) is a list of hooks to be run immediately after the container process is started
260
* [`Poststop`](#poststop) is a list of hooks to be run after the container process exits
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Hooks allow one to run code before/after various lifecycle events of the container.
263
Hooks MUST be called in the listed order.
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The state of the container is passed to the hooks over stdin, so the hooks could get the information they need to do their work.
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Hook paths are absolute and are executed from the host's filesystem in the [runtime namespace][runtime-namespace].
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### Prestart
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The pre-start hooks are called after the container process is spawned, but before the user supplied command is executed.
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They are called after the container namespaces are created on Linux, so they provide an opportunity to customize the container.
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In Linux, for e.g., the network namespace could be configured in this hook.
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If a hook returns a non-zero exit code, then an error including the exit code and the stderr is returned to the caller and the container is torn down.
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### Poststart
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The post-start hooks are called after the user process is started.
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For example this hook can notify user that real process is spawned.
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If a hook returns a non-zero exit code, then an error is logged and the remaining hooks are executed.
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### Poststop
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The post-stop hooks are called after the container process is stopped.
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Cleanup or debugging could be performed in such a hook.
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If a hook returns a non-zero exit code, then an error is logged and the remaining hooks are executed.
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### Example
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```json
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"hooks" : {
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"prestart": [
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{
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"path": "/usr/bin/fix-mounts",
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"args": ["fix-mounts", "arg1", "arg2"],
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"env": [ "key1=value1"]
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},
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{
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"path": "/usr/bin/setup-network"
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}
302
],
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"poststart": [
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{
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"path": "/usr/bin/notify-start",
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"timeout": 5
307
}
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],
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"poststop": [
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{
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"path": "/usr/sbin/cleanup.sh",
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"args": ["cleanup.sh", "-f"]
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}
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]
315
}
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```
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`path` is required for a hook.
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`args` and `env` are optional.
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`timeout` is the number of seconds before aborting the hook.
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The semantics are the same as `Path`, `Args` and `Env` in [golang Cmd](https://golang.org/pkg/os/exec/#Cmd).
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## Annotations
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**`annotations`** (object, optional) contains arbitrary metadata for the container.
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This information MAY be structured or unstructured.
327
Annotations are key-value maps.
328
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```json
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"annotations": {
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"key1" : "value1",
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"key2" : "value2"
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}
334
```
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## Configuration Schema Example
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Here is a full example `config.json` for reference.
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```json
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{
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"ociVersion": "0.5.0-dev",
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"platform": {
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"os": "linux",
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"arch": "amd64"
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},
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"process": {
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"terminal": true,
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"user": {
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"uid": 1,
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"gid": 1,
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"additionalGids": [
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5,
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6
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]
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},
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"args": [
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"sh"
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],
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"env": [
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"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
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"TERM=xterm"
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],
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"cwd": "/",
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"capabilities": [
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"CAP_AUDIT_WRITE",
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"CAP_KILL",
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"CAP_NET_BIND_SERVICE"
369
],
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"rlimits": [
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{
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"type": "RLIMIT_CORE",
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"hard": 1024,
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"soft": 1024
375
},
376
{
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"type": "RLIMIT_NOFILE",
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"hard": 1024,
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"soft": 1024
380
}
381
],
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"apparmorProfile": "acme_secure_profile",
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"selinuxLabel": "system_u:system_r:svirt_lxc_net_t:s0:c124,c675",
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"noNewPrivileges": true
385
},
386
"root": {
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"path": "rootfs",
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"readonly": true
389
},
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"hostname": "slartibartfast",
391
"mounts": [
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{
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"destination": "/proc",
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"type": "proc",
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"source": "proc"
396
},
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{
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"destination": "/dev",
399
"type": "tmpfs",
400
"source": "tmpfs",
401
"options": [
402
"nosuid",
403
"strictatime",
404
"mode=755",
405
"size=65536k"
406
]
407
},
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{
409
"destination": "/dev/pts",
410
"type": "devpts",
411
"source": "devpts",
412
"options": [
413
"nosuid",
414
"noexec",
415
"newinstance",
416
"ptmxmode=0666",
417
"mode=0620",
418
"gid=5"
419
]
420
},
421
{
422
"destination": "/dev/shm",
423
"type": "tmpfs",
424
"source": "shm",
425
"options": [
426
"nosuid",
427
"noexec",
428
"nodev",
429
"mode=1777",
430
"size=65536k"
431
]
432
},
433
{
434
"destination": "/dev/mqueue",
435
"type": "mqueue",
436
"source": "mqueue",
437
"options": [
438
"nosuid",
439
"noexec",
440
"nodev"
441
]
442
},
443
{
444
"destination": "/sys",
445
"type": "sysfs",
446
"source": "sysfs",
447
"options": [
448
"nosuid",
449
"noexec",
450
"nodev"
451
]
452
},
453
{
454
"destination": "/sys/fs/cgroup",
455
"type": "cgroup",
456
"source": "cgroup",
457
"options": [
458
"nosuid",
459
"noexec",
460
"nodev",
461
"relatime",
462
"ro"
463
]
464
}
465
],
466
"hooks": {
467
"prestart": [
468
{
469
"path": "/usr/bin/fix-mounts",
470
"args": [
471
"fix-mounts",
472
"arg1",
473
"arg2"
475
"env": [
476
"key1=value1"
477
]
478
},
479
{
480
"path": "/usr/bin/setup-network"
481
}
482
],
483
"poststart": [
484
{
485
"path": "/usr/bin/notify-start",
486
"timeout": 5
487
}
488
],
489
"poststop": [
490
{
491
"path": "/usr/sbin/cleanup.sh",
492
"args": [
493
"cleanup.sh",
494
"-f"
495
]
496
}
497
]
498
},
499
"linux": {
500
"devices": [
501
{
502
"path": "/dev/fuse",
503
"type": "c",
504
"major": 10,
505
"minor": 229,
506
"fileMode": 438,
507
"uid": 0,
508
"gid": 0
509
},
510
{
511
"path": "/dev/sda",
512
"type": "b",
513
"major": 8,
514
"minor": 0,
515
"fileMode": 432,
516
"uid": 0,
517
"gid": 0
518
}
519
],
520
"uidMappings": [
521
{
522
"hostID": 1000,
523
"containerID": 0,
524
"size": 32000
525
}
526
],
527
"gidMappings": [
528
{
529
"hostID": 1000,
530
"containerID": 0,
531
"size": 32000
532
}
533
],
534
"sysctl": {
535
"net.ipv4.ip_forward": "1",
536
"net.core.somaxconn": "256"
537
},
538
"cgroupsPath": "/myRuntime/myContainer",
539
"resources": {
540
"network": {
541
"classID": 1048577,
542
"priorities": [
543
{
544
"name": "eth0",
545
"priority": 500
546
},
547
{
548
"name": "eth1",
549
"priority": 1000
550
}
551
]
552
},
553
"pids": {
554
"limit": 32771
555
},
556
"hugepageLimits": [
557
{
558
"pageSize": "2MB",
559
"limit": 9223372036854772000
560
}
561
],
562
"oomScoreAdj": 100,
563
"memory": {
564
"limit": 536870912,
565
"reservation": 536870912,
566
"swap": 536870912,
567
"kernel": 0,
568
"kernelTCP": 0,
569
"swappiness": 0
570
},
571
"cpu": {
572
"shares": 1024,
573
"quota": 1000000,
574
"period": 500000,
575
"realtimeRuntime": 950000,
576
"realtimePeriod": 1000000,
577
"cpus": "2-3",
578
"mems": "0-7"
579
},
580
"disableOOMKiller": false,
581
"devices": [
582
{
583
"allow": false,
584
"access": "rwm"
585
},
586
{
587
"allow": true,
588
"type": "c",
589
"major": 10,
590
"minor": 229,
591
"access": "rw"
592
},
593
{
594
"allow": true,
595
"type": "b",
596
"major": 8,
597
"minor": 0,
598
"access": "r"
599
}
600
],
601
"blockIO": {
602
"blkioWeight": 10,
603
"blkioLeafWeight": 10,
604
"blkioWeightDevice": [
605
{
606
"major": 8,
607
"minor": 0,
608
"weight": 500,
609
"leafWeight": 300
610
},
611
{
612
"major": 8,
613
"minor": 16,
614
"weight": 500
615
}
616
],
617
"blkioThrottleReadBpsDevice": [
618
{
619
"major": 8,
620
"minor": 0,
621
"rate": 600
622
}
623
],
624
"blkioThrottleWriteIOPSDevice": [
625
{
626
"major": 8,
627
"minor": 16,
628
"rate": 300
629
}
630
]
631
}
632
},
633
"rootfsPropagation": "slave",
634
"seccomp": {
635
"defaultAction": "SCMP_ACT_ALLOW",
636
"architectures": [
637
"SCMP_ARCH_X86"
638
],
639
"syscalls": [
640
{
641
"name": "getcwd",
642
"action": "SCMP_ACT_ERRNO"
643
}
644
]
645
},
646
"namespaces": [
647
{
648
"type": "pid"
649
},
650
{
651
"type": "network"
652
},
653
{
654
"type": "ipc"
655
},
656
{
657
"type": "uts"
658
},
659
{
660
"type": "mount"
661
},
662
{
663
"type": "user"
664
},
665
{
666
"type": "cgroup"
668
],
669
"maskedPaths": [
670
"/proc/kcore",
671
"/proc/latency_stats",
672
"/proc/timer_stats",
673
"/proc/sched_debug"
674
],
675
"readonlyPaths": [
676
"/proc/asound",
677
"/proc/bus",
678
"/proc/fs",
679
"/proc/irq",
680
"/proc/sys",
681
"/proc/sysrq-trigger"
682
],
683
"mountLabel": "system_u:object_r:svirt_sandbox_file_t:s0:c715,c811"
684
},
685
"annotations": {
686
"key1": "value1",
687
"key2": "value2"
689
}
690
```
691
692
[container-namespace]: glossary.md#container-namespace
693
[go-environment]: https://golang.org/doc/install/source#environment
694
[runtime-namespace]: glossary.md#runtime-namespace
695
[uts-namespace]: http://man7.org/linux/man-pages/man7/namespaces.7.html
696
[mount.8-filesystem-independent]: http://man7.org/linux/man-pages/man8/mount.8.html#FILESYSTEM-INDEPENDENT_MOUNT OPTIONS
697
[mount.8-filesystem-specific]: http://man7.org/linux/man-pages/man8/mount.8.html#FILESYSTEM-SPECIFIC_MOUNT OPTIONS
698
[mount.8]: http://man7.org/linux/man-pages/man8/mount.8.html