From fc6dcd12b3430f2d1ee495ef19d184a088f3bb34 Mon Sep 17 00:00:00 2001 From: Matthew Heon Date: Fri, 16 Sep 2022 15:00:37 -0400 Subject: Add support for 'image' volume driver We added the concept of image volumes in 2.2.0, to support inspecting an image from within a container. However, this is a strictly read-only mount, with no modification allowed. By contrast, the new `image` volume driver creates a c/storage container as its underlying storage, so we have a read/write layer. This, in and of itself, is not especially interesting, but what it will enable in the future is. If we add a new command to allow these image volumes to be committed, we can now distribute volumes - and changes to them - via a standard OCI image registry (which is rather new and quite exciting). Future work in this area: - Add support for `podman volume push` (commit volume changes and push resulting image to OCI registry). - Add support for `podman volume pull` (currently, we require that the image a volume is created from be already pulled; it would be simpler if we had a dedicated command that did the pull and made a volume from it) - Add support for scratch images (make an empty image on demand to use as the base of the volume) - Add UOR support to `podman volume push` and `podman volume pull` to enable both with non-image volume drivers Signed-off-by: Matthew Heon --- docs/source/markdown/podman-volume-create.1.md | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) (limited to 'docs') diff --git a/docs/source/markdown/podman-volume-create.1.md b/docs/source/markdown/podman-volume-create.1.md index 934488111..1e99df55a 100644 --- a/docs/source/markdown/podman-volume-create.1.md +++ b/docs/source/markdown/podman-volume-create.1.md @@ -17,7 +17,13 @@ driver options can be set using the **--opt** flag. #### **--driver**=*driver* -Specify the volume driver name (default **local**). Setting this to a value other than **local** Podman attempts to create the volume using a volume plugin with the given name. Such plugins must be defined in the **volume_plugins** section of the **[containers.conf(5)](https://github.com/containers/common/blob/main/docs/containers.conf.5.md)** configuration file. +Specify the volume driver name (default **local**). +There are two drivers supported by Podman itself: **local** and **image**. +The **local** driver uses a directory on disk as the backend by default, but can also use the **mount(8)** command to mount a filesystem as the volume if **--opt** is specified. +The **image** driver uses an image as the backing store of for the volume. +An overlay filesystem will be created, which allows changes to the volume to be committed as a new layer on top of the image. +Using a value other than **local or **image**, Podman will attempt to create the volume using a volume plugin with the given name. +Such plugins must be defined in the **volume_plugins** section of the **[containers.conf(5)](https://github.com/containers/common/blob/main/docs/containers.conf.5.md)** configuration file. #### **--help** @@ -43,7 +49,10 @@ The `o` option sets options for the mount, and is equivalent to the `-o` flag to - The `o` option supports using volume options other than the UID/GID options with the **local** driver and requires root privileges. - The `o` options supports the `timeout` option which allows users to set a driver specific timeout in seconds before volume creation fails. For example, **--opts=o=timeout=10** sets a driver timeout of 10 seconds. -When not using the **local** driver, the given options are passed directly to the volume plugin. In this case, supported options are dictated by the plugin in question, not Podman. +For the **image** driver, the only supported option is `image`, which specifies the image the volume is based on. +This option is mandatory when using the **image** driver. + +When not using the **local** and **image** drivers, the given options are passed directly to the volume plugin. In this case, supported options are dictated by the plugin in question, not Podman. ## EXAMPLES @@ -57,6 +66,8 @@ $ podman volume create --label foo=bar myvol # podman volume create --opt device=tmpfs --opt type=tmpfs --opt o=nodev,noexec myvol # podman volume create --opt device=tmpfs --opt type=tmpfs --opt o=uid=1000,gid=1000 testvol + +# podman volume create --driver image --opt image=fedora:latest fedoraVol ``` ## QUOTAS -- cgit v1.2.3-54-g00ecf