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storage: document how to set mount opts with --tmpfs 

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>
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David Karlsson 2024-12-20 15:17:57 +01:00
parent 6c8c8f874b
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content/manuals/engine/storage/tmpfs.md
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@ -60,10 +60,67 @@ $ docker run --tmpfs <mount-path>
```
In general, `--mount` is preferred. The main difference is that the `--mount`
flag is more explicit and supports all the available options.
flag is more explicit. On the other hand, `--tmpfs` is less verbose and gives
you more flexibility as it lets you set more mount options.
The `--tmpfs` flag cannot be used with swarm services. You must use `--mount`.
### Options for --tmpfs
The `--tmpfs` flag consists of two fields, separated by a colon character
(`:`).
```console
$ docker run --tmpfs <mount-path>[:opts]
```
The first field is the container path to mount into a tmpfs. The second field
is optional and lets you set mount options. Valid mount options for `--tmpfs`
include:
| Option | Description |
| ------------ | ------------------------------------------------------------------------------------------- |
| `ro` | Creates a read-only tmpfs mount. |
| `rw` | Creates a read-write tmpfs mount (default behavior). |
| `nosuid` | Prevents `setuid` and `setgid` bits from being honored during execution. |
| `suid` | Allows `setuid` and `setgid` bits to be honored during execution (default behavior). |
| `nodev` | Device files can be created but are not functional (access results in an error). |
| `dev` | Device files can be created and are fully functional. |
| `exec` | Allows the execution of executable binaries in the mounted file system. |
| `noexec` | Does not allow the execution of executable binaries in the mounted file system. |
| `sync` | All I/O to the file system is done synchronously. |
| `async` | All I/O to the file system is done asynchronously (default behavior). |
| `dirsync` | Directory updates within the file system are done synchronously. |
| `atime` | Updates file access time each time the file is accessed. |
| `noatime` | Does not update file access times when the file is accessed. |
| `diratime` | Updates directory access times each time the directory is accessed. |
| `nodiratime` | Does not update directory access times when the directory is accessed. |
| `size` | Specifies the size of the tmpfs mount, for example, `size=64m`. |
| `mode` | Specifies the file mode (permissions) for the tmpfs mount (for example, `mode=1777`). |
| `uid` | Specifies the user ID for the owner of the tmpfs mount (for example, `uid=1000`). |
| `gid` | Specifies the group ID for the owner of the tmpfs mount (for example, `gid=1000`). |
| `nr_inodes` | Specifies the maximum number of inodes for the tmpfs mount (for example, `nr_inodes=400k`). |
| `nr_blocks` | Specifies the maximum number of blocks for the tmpfs mount (for example, `nr_blocks=1024`). |
```console {title="Example"}
$ docker run --tmpfs /data:noexec,size=1024,mode=1777
```
Not all tmpfs mount features available in the Linux mount command are supported
with the `--tmpfs` flag. If you require advanced tmpfs options or features, you
may need to use a privileged container or configure the mount outside of
Docker.
> [!CAUTION]
> Running containers with `--privileged` grants elevated permissions and can
> expose the host system to security risks. Use this option only when
> absolutely necessary and in trusted environments.
```console
$ docker run --privileged -it debian sh
/# mount -t tmpfs -o <options> tmpfs /data
```
### Options for --mount
The `--mount` flag consists of multiple key-value pairs, separated by commas
@ -86,10 +143,6 @@ Valid options for `--mount type=tmpfs` include:
$ docker run --mount type=tmpfs,dst=/app,tmpfs-size=21474836480,tmpfs-mode=1770
```
### Options for --tmpfs
The `--tmpfs` flag does not let you specify any options.
## Use a tmpfs mount in a container
To use a `tmpfs` mount in a container, use the `--tmpfs` flag, or use the