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config: clarify Linux mount options
The former wording was inconsistent with runc, crun, youki, etc. Several `mount(8)` options such as `X-mount.mode` are unimplemented in those OCI runtimes, and vice versa (`tmpcopyup`, `rro`, etc.) The option table added in this commit conforms to runc 1.1, but `acl` and `noacl` are excluded as the runc implementation seems wrong (runc issue 3738). Signed-off-by: Akihiro Suda <[email protected]>
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‎config.md

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@@ -77,11 +77,87 @@ For Solaris, the mount entry corresponds to the 'fs' resource in the [zonecfg(1M
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* Windows: a local directory on the filesystem of the container host. UNC paths and mapped drives are not supported.
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* Solaris: corresponds to "special" of the fs resource in [zonecfg(1M)][zonecfg.1m].
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* **`options`** (array of strings, OPTIONAL) Mount options of the filesystem to be used.
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* Linux: supported options are listed in the [mount(8)][mount.8] man page.
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Note both [filesystem-independent][mount.8-filesystem-independent] and [filesystem-specific][mount.8-filesystem-specific] options are listed.
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* Linux: See [Linux mount options](#configLinuxMountOptions) below.
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* Solaris: corresponds to "options" of the fs resource in [zonecfg(1M)][zonecfg.1m].
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* Windows: runtimes MUST support `ro`, mounting the filesystem read-only when `ro` is given.
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### <a name="configLinuxMountOptions" />Linux mount options
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Runtimes MUST/SHOULD/MAY implement the following option strings for Linux:
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Option name | Requirement | Description
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------------------|-------------|-----------------------------------------------------
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`async` | MUST | [^1]
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`atime` | MUST | [^1]
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`bind` | MUST | [^2] (bind mounts)
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`defaults` | MUST | [^1]
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`dev` | MUST | [^1]
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`diratime` | MUST | [^1]
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`dirsync` | MUST | [^1]
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`exec` | MUST | [^1]
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`iversion` | MUST | [^1]
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`lazytime` | MUST | [^1]
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`loud` | MUST | [^1]
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`mand` | MAY | [^1] (Deprecated in kernel 5.15, util-linux 2.38)
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`noatime` | MUST | [^1]
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`nodev` | MUST | [^1]
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`nodiratime` | MUST | [^1]
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`noexec` | MUST | [^1]
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`noiversion` | MUST | [^1]
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`nolazytime` | MUST | [^1]
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`nomand` | MAY | [^1]
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`norelatime` | MUST | [^1]
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`nostrictatime` | MUST | [^1]
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`nosuid` | MUST | [^1]
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`nosymfollow` | SHOULD | [^1] (Introduced in kernel 5.10, util-linux 2.38)
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`private` | MUST | [^2] (bind mounts)
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`ratime` | SHOULD | Recursive `atime` [^3]
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`rbind` | MUST | [^2] (bind mounts)
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`rdev` | SHOULD | Recursive `dev` [^3]
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`rdiratime` | SHOULD | Recursive `diratime` [^3]
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`relatime` | MUST | [^1]
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`remount` | MUST | [^1]
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`rexec` | SHOULD | Recursive `dev` [^3]
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`rnoatime` | SHOULD | Recursive `noatime` [^3]
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`rnodiratime` | SHOULD | Recursive `nodiratime` [^3]
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`rnoexec` | SHOULD | Recursive `noexec` [^3]
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`rnorelatime` | SHOULD | Recursive `norelatime` [^3]
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`rnostrictatime` | SHOULD | Recursive `nostrictatime` [^3]
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`rnosuid` | SHOULD | Recursive `nosuid` [^3]
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`rnosymfollow` | SHOULD | Recursive `nosymfollow` [^3]
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`ro` | MUST | [^1]
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`rprivate` | MUST | [^2] (bind mounts)
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`rrelatime ` | SHOULD | Recursive `relatime` [^3]
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`rro` | SHOULD | Recursive `ro` [^3]
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`rrw` | SHOULD | Recursive `rw` [^3]
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`rshared` | MUST | [^2] (bind mounts)
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`rslave` | MUST | [^2] (bind mounts)
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`rstrictatime` | SHOULD | Recursive `strictatime` [^3]
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`rsuid` | SHOULD | Recursive `suid` [^3]
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`rsymfollow` | SHOULD | Recursive `symfollow` [^3]
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`runbindable` | MUST | [^2] (bind mounts)
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`rw` | MUST | [^1]
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`shared` | MUST | [^1]
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`silent` | MUST | [^1]
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`slave` | MUST | [^2] (bind mounts)
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`strictatime` | MUST | [^1]
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`suid` | MUST | [^1]
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`symfollow` | SHOULD | Opposite of `nosymfollow`
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`sync` | MUST | [^1]
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`tmpcopyup` | MAY | copy up the contents to a tmpfs
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`unbindable` | MUST | [^2] (bind mounts)
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[^1]: Corresponds to [`mount(8)` (filesystem-independent)][mount.8-filesystem-independent].
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[^2]: Corresponds to [`mount(8)` (filesystem-specific)][mount.8-filesystem-specific].
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[^3]: These `AT_RECURSIVE` options need kernel 5.12 or later. See [`mount_setattr(2)`][mount_setattr.2]
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The "MUST" options correspond to [`mount(8)`][mount.8].
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Runtimes MAY also implement custom option strings that are not listed in the table above.
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If a custom option string is already recognized by [`mount(8)`][mount.8], the runtime SHOULD follow the behavior of [`mount(8)`][mount.8].
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Runtimes SHOULD pass unknown options to [`mount(2)`][mount.2] via the fifth argument (`const void *data`).
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### Example (Windows)
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```json
@@ -1004,6 +1080,7 @@ Here is a full example `config.json` for reference.
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[mount.8]: http://man7.org/linux/man-pages/man8/mount.8.html
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[mount.8-filesystem-independent]: http://man7.org/linux/man-pages/man8/mount.8.html#FILESYSTEM-INDEPENDENT_MOUNT_OPTIONS
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[mount.8-filesystem-specific]: http://man7.org/linux/man-pages/man8/mount.8.html#FILESYSTEM-SPECIFIC_MOUNT_OPTIONS
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[mount_setattr.2]: http://man7.org/linux/man-pages/man2/mount_setattr.2.html
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[getrlimit.2]: http://man7.org/linux/man-pages/man2/getrlimit.2.html
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[getrlimit.3]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/getrlimit.html
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[stdin.3]: http://man7.org/linux/man-pages/man3/stdin.3.html

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