diff options
Diffstat (limited to 'docs/source/markdown/options')
26 files changed, 482 insertions, 1 deletions
diff --git a/docs/source/markdown/options/README.md b/docs/source/markdown/options/README.md index 92f3d374e..d8b608fb7 100644 --- a/docs/source/markdown/options/README.md +++ b/docs/source/markdown/options/README.md @@ -43,4 +43,5 @@ This allows the shared use of examples in the option file: Example: podman <<subcommand>> --foo --bar ``` As a special case, `podman-pod-X` becomes just `X` (the "pod" is removed). -This makes the `pod-id-file` man page more useful. +This makes the `pod-id-file` man page more useful. To get the full +subcommand including 'pod', use `<<fullsubcommand>>`. diff --git a/docs/source/markdown/options/device-read-bps.md b/docs/source/markdown/options/device-read-bps.md new file mode 100644 index 000000000..f6617ab77 --- /dev/null +++ b/docs/source/markdown/options/device-read-bps.md @@ -0,0 +1,9 @@ +#### **--device-read-bps**=*path:rate* + +Limit read rate (in bytes per second) from a device (e.g. **--device-read-bps=/dev/sda:1mb**). + +On some systems, changing the resource limits may not be allowed for non-root +users. For more details, see +https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error + +This option is not supported on cgroups V1 rootless systems. diff --git a/docs/source/markdown/options/device-read-iops.md b/docs/source/markdown/options/device-read-iops.md new file mode 100644 index 000000000..944c66441 --- /dev/null +++ b/docs/source/markdown/options/device-read-iops.md @@ -0,0 +1,9 @@ +#### **--device-read-iops**=*path:rate* + +Limit read rate (in IO operations per second) from a device (e.g. **--device-read-iops=/dev/sda:1000**). + +On some systems, changing the resource limits may not be allowed for non-root +users. For more details, see +https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error + +This option is not supported on cgroups V1 rootless systems. diff --git a/docs/source/markdown/options/device-write-bps.md b/docs/source/markdown/options/device-write-bps.md new file mode 100644 index 000000000..ebcda0181 --- /dev/null +++ b/docs/source/markdown/options/device-write-bps.md @@ -0,0 +1,9 @@ +#### **--device-write-bps**=*path:rate* + +Limit write rate (in bytes per second) to a device (e.g. **--device-write-bps=/dev/sda:1mb**). + +On some systems, changing the resource limits may not be allowed for non-root +users. For more details, see +https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error + +This option is not supported on cgroups V1 rootless systems. diff --git a/docs/source/markdown/options/device-write-iops.md b/docs/source/markdown/options/device-write-iops.md new file mode 100644 index 000000000..6de273d18 --- /dev/null +++ b/docs/source/markdown/options/device-write-iops.md @@ -0,0 +1,9 @@ +#### **--device-write-iops**=*path:rate* + +Limit write rate (in IO operations per second) to a device (e.g. **--device-write-iops=/dev/sda:1000**). + +On some systems, changing the resource limits may not be allowed for non-root +users. For more details, see +https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error + +This option is not supported on cgroups V1 rootless systems. diff --git a/docs/source/markdown/options/device.md b/docs/source/markdown/options/device.md new file mode 100644 index 000000000..619c70a9b --- /dev/null +++ b/docs/source/markdown/options/device.md @@ -0,0 +1,14 @@ +#### **--device**=*host-device[:container-device][:permissions]* + +Add a host device to the <<container|pod>>. Optional *permissions* parameter +can be used to specify device permissions by combining +**r** for read, **w** for write, and **m** for **mknod**(2). + +Example: **--device=/dev/sdc:/dev/xvdc:rwm**. + +Note: if *host-device* is a symbolic link then it will be resolved first. +The <<container|pod>> will only store the major and minor numbers of the host device. + +Podman may load kernel modules required for using the specified +device. The devices that Podman will load modules for when necessary are: +/dev/fuse. diff --git a/docs/source/markdown/options/digestfile.md b/docs/source/markdown/options/digestfile.md new file mode 100644 index 000000000..de013e287 --- /dev/null +++ b/docs/source/markdown/options/digestfile.md @@ -0,0 +1,4 @@ +#### **--digestfile**=*Digestfile* + +After copying the image, write the digest of the resulting image to the file. +(This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines) diff --git a/docs/source/markdown/options/dns-opt.container.md b/docs/source/markdown/options/dns-opt.container.md new file mode 100644 index 000000000..ea26fd013 --- /dev/null +++ b/docs/source/markdown/options/dns-opt.container.md @@ -0,0 +1,3 @@ +#### **--dns-opt**=*option* + +Set custom DNS options. Invalid if using **--dns-opt** with **--network** that is set to **none** or **container:**_id_. diff --git a/docs/source/markdown/options/dns-search.container.md b/docs/source/markdown/options/dns-search.container.md new file mode 100644 index 000000000..5a803ba39 --- /dev/null +++ b/docs/source/markdown/options/dns-search.container.md @@ -0,0 +1,4 @@ +#### **--dns-search**=*domain* + +Set custom DNS search domains. Invalid if using **--dns-search** with **--network** that is set to **none** or **container:**_id_. +Use **--dns-search=.** if you don't wish to set the search domain. diff --git a/docs/source/markdown/options/health-on-failure.md b/docs/source/markdown/options/health-on-failure.md new file mode 100644 index 000000000..c25a1c574 --- /dev/null +++ b/docs/source/markdown/options/health-on-failure.md @@ -0,0 +1,8 @@ +#### **--health-on-failure**=*action* + +Action to take once the container transitions to an unhealthy state. The default is **none**. + +- **none**: Take no action. +- **kill**: Kill the container. +- **restart**: Restart the container. Do not combine the `restart` action with the `--restart` flag. When running inside of a systemd unit, consider using the `kill` or `stop` action instead to make use of systemd's restart policy. +- **stop**: Stop the container. diff --git a/docs/source/markdown/options/http-proxy.md b/docs/source/markdown/options/http-proxy.md new file mode 100644 index 000000000..f83dcde4a --- /dev/null +++ b/docs/source/markdown/options/http-proxy.md @@ -0,0 +1,15 @@ +#### **--http-proxy** + +By default proxy environment variables are passed into the container if set +for the Podman process. This can be disabled by setting the value to **false**. +The environment variables passed in include **http_proxy**, +**https_proxy**, **ftp_proxy**, **no_proxy**, and also the upper case versions of +those. This option is only needed when the host system must use a proxy but +the container should not use any proxy. Proxy environment variables specified +for the container in any other way will override the values that would have +been passed through from the host. (Other ways to specify the proxy for the +container include passing the values with the **--env** flag, or hard coding the +proxy environment at container build time.) +(This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines) + +Defaults to **true**. diff --git a/docs/source/markdown/options/label.md b/docs/source/markdown/options/label.md new file mode 100644 index 000000000..629aa82e6 --- /dev/null +++ b/docs/source/markdown/options/label.md @@ -0,0 +1,3 @@ +#### **--label**, **-l**=*key=value* + +Add metadata to a <<container|pod>>. diff --git a/docs/source/markdown/options/memory-reservation.md b/docs/source/markdown/options/memory-reservation.md new file mode 100644 index 000000000..410f1dd7c --- /dev/null +++ b/docs/source/markdown/options/memory-reservation.md @@ -0,0 +1,11 @@ +#### **--memory-reservation**=*number[unit]* + +Memory soft limit. A _unit_ can be **b** (bytes), **k** (kibibytes), **m** (mebibytes), or **g** (gibibytes). + +After setting memory reservation, when the system detects memory contention +or low memory, containers are forced to restrict their consumption to their +reservation. So you should always set the value below **--memory**, otherwise the +hard limit will take precedence. By default, memory reservation will be the same +as memory limit. + +This option is not supported on cgroups V1 rootless systems. diff --git a/docs/source/markdown/options/memory-swap.md b/docs/source/markdown/options/memory-swap.md new file mode 100644 index 000000000..08ee8b1a0 --- /dev/null +++ b/docs/source/markdown/options/memory-swap.md @@ -0,0 +1,13 @@ +#### **--memory-swap**=*number[unit]* + +A limit value equal to memory plus swap. +A _unit_ can be **b** (bytes), **k** (kibibytes), **m** (mebibytes), or **g** (gibibytes). + +Must be used with the **-m** (**--memory**) flag. +The argument value should always be larger than that of + **-m** (**--memory**) By default, it is set to double +the value of **--memory**. + +Set _number_ to **-1** to enable unlimited swap. + +This option is not supported on cgroups V1 rootless systems. diff --git a/docs/source/markdown/options/memory.md b/docs/source/markdown/options/memory.md new file mode 100644 index 000000000..1be9159c3 --- /dev/null +++ b/docs/source/markdown/options/memory.md @@ -0,0 +1,11 @@ +#### **--memory**, **-m**=*number[unit]* + +Memory limit. A _unit_ can be **b** (bytes), **k** (kibibytes), **m** (mebibytes), or **g** (gibibytes). + +Allows the memory available to a container to be constrained. If the host +supports swap memory, then the **-m** memory setting can be larger than physical +RAM. If a limit of 0 is specified (not using **-m**), the container's memory is +not limited. The actual limit may be rounded up to a multiple of the operating +system's page size (the value would be very large, that's millions of trillions). + +This option is not supported on cgroups V1 rootless systems. diff --git a/docs/source/markdown/options/name.container.md b/docs/source/markdown/options/name.container.md new file mode 100644 index 000000000..0c3df6ef1 --- /dev/null +++ b/docs/source/markdown/options/name.container.md @@ -0,0 +1,14 @@ +#### **--name**=*name* + +Assign a name to the container. + +The operator can identify a container in three ways: + +- UUID long identifier (“f78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778”); +- UUID short identifier (“f78375b1c487”); +- Name (“jonah”). + +Podman generates a UUID for each container, and if a name is not assigned +to the container with **--name** then it will generate a random +string name. The name is useful any place you need to identify a container. +This works for both background and foreground containers. diff --git a/docs/source/markdown/options/privileged.md b/docs/source/markdown/options/privileged.md new file mode 100644 index 000000000..8d9746d6b --- /dev/null +++ b/docs/source/markdown/options/privileged.md @@ -0,0 +1,14 @@ +#### **--privileged** + +Give extended privileges to this container. The default is **false**. + +By default, Podman containers are unprivileged (**=false**) and cannot, for +example, modify parts of the operating system. This is because by default a +container is only allowed limited access to devices. A "privileged" container +is given the same access to devices as the user launching the container. + +A privileged container turns off the security features that isolate the +container from the host. Dropped Capabilities, limited devices, read-only mount +points, Apparmor/SELinux separation, and Seccomp filters are all disabled. + +Rootless containers cannot have more privileges than the account that launched them. diff --git a/docs/source/markdown/options/restart.md b/docs/source/markdown/options/restart.md new file mode 100644 index 000000000..825ae613f --- /dev/null +++ b/docs/source/markdown/options/restart.md @@ -0,0 +1,15 @@ +#### **--restart**=*policy* + +Restart policy to follow when containers exit. +Restart policy will not take effect if a container is stopped via the **podman kill** or **podman stop** commands. + +Valid _policy_ values are: + +- `no` : Do not restart containers on exit +- `on-failure[:max_retries]` : Restart containers when they exit with a non-zero exit code, retrying indefinitely or until the optional *max_retries* count is hit +- `always` : Restart containers when they exit, regardless of status, retrying indefinitely +- `unless-stopped` : Identical to **always** + +Please note that restart will not restart containers after a system reboot. +If this functionality is required in your environment, you can invoke Podman from a **systemd.unit**(5) file, or create an init script for whichever init system is in use. +To generate systemd unit files, please see **podman generate systemd**. diff --git a/docs/source/markdown/options/signal.md b/docs/source/markdown/options/signal.md new file mode 100644 index 000000000..6e6c03657 --- /dev/null +++ b/docs/source/markdown/options/signal.md @@ -0,0 +1,4 @@ +#### **--signal**, **-s**=**signal** + +Signal to send to the container<<|s in the pod>>. For more information on Linux signals, refer to *signal(7)*. +The default is **SIGKILL**. diff --git a/docs/source/markdown/options/subgidname.md b/docs/source/markdown/options/subgidname.md new file mode 100644 index 000000000..1ca0496d0 --- /dev/null +++ b/docs/source/markdown/options/subgidname.md @@ -0,0 +1,5 @@ +#### **--subgidname**=*name* + +Run the container in a new user namespace using the map with _name_ in the _/etc/subgid_ file. +If running rootless, the user needs to have the right to use the mapping. See **subgid**(5). +This flag conflicts with **--userns** and **--gidmap**. diff --git a/docs/source/markdown/options/subuidname.md b/docs/source/markdown/options/subuidname.md new file mode 100644 index 000000000..bd7b61575 --- /dev/null +++ b/docs/source/markdown/options/subuidname.md @@ -0,0 +1,5 @@ +#### **--subuidname**=*name* + +Run the container in a new user namespace using the map with _name_ in the _/etc/subuid_ file. +If running rootless, the user needs to have the right to use the mapping. See **subuid**(5). +This flag conflicts with **--userns** and **--uidmap**. diff --git a/docs/source/markdown/options/sysctl.md b/docs/source/markdown/options/sysctl.md new file mode 100644 index 000000000..6fc1bbebe --- /dev/null +++ b/docs/source/markdown/options/sysctl.md @@ -0,0 +1,21 @@ +#### **--sysctl**=*name=value* + +Configure namespaced kernel parameters <<at runtime|for all containers in the pod>>. + +For the IPC namespace, the following sysctls are allowed: + +- kernel.msgmax +- kernel.msgmnb +- kernel.msgmni +- kernel.sem +- kernel.shmall +- kernel.shmmax +- kernel.shmmni +- kernel.shm_rmid_forced +- Sysctls beginning with fs.mqueue.\* + +Note: <<if you use the **--ipc=host** option|if the ipc namespace is not shared within the pod>>, the above sysctls are not allowed. + +For the network namespace, only sysctls beginning with net.\* are allowed. + +Note: <<if you use the **--network=host** option|if the network namespace is not shared within the pod>>, the above sysctls are not allowed. diff --git a/docs/source/markdown/options/systemd.md b/docs/source/markdown/options/systemd.md new file mode 100644 index 000000000..a341edbc2 --- /dev/null +++ b/docs/source/markdown/options/systemd.md @@ -0,0 +1,29 @@ +#### **--systemd**=*true* | *false* | *always* + +Run container in systemd mode. The default is **true**. + +The value *always* enforces the systemd mode is enforced without +looking at the executable name. Otherwise, if set to true and the +command you are running inside the container is **systemd**, **/usr/sbin/init**, +**/sbin/init** or **/usr/local/sbin/init**. + +Running the container in systemd mode causes the following changes: + +* Podman mounts tmpfs file systems on the following directories + * _/run_ + * _/run/lock_ + * _/tmp_ + * _/sys/fs/cgroup/systemd_ + * _/var/lib/journal_ +* Podman sets the default stop signal to **SIGRTMIN+3**. +* Podman sets **container_uuid** environment variable in the container to the +first 32 characters of the container id. + +This allows systemd to run in a confined container without any modifications. + +Note that on **SELinux** systems, systemd attempts to write to the cgroup +file system. Containers writing to the cgroup file system are denied by default. +The **container_manage_cgroup** boolean must be enabled for this to be allowed on an SELinux separated system. +``` +setsebool -P container_manage_cgroup true +``` diff --git a/docs/source/markdown/options/userns.container.md b/docs/source/markdown/options/userns.container.md new file mode 100644 index 000000000..8f96892df --- /dev/null +++ b/docs/source/markdown/options/userns.container.md @@ -0,0 +1,47 @@ +#### **--userns**=*mode* + +Set the user namespace mode for the container. It defaults to the **PODMAN_USERNS** environment variable. An empty value ("") means user namespaces are disabled unless an explicit mapping is set with the **--uidmap** and **--gidmap** options. + +This option is incompatible with **--gidmap**, **--uidmap**, **--subuidname** and **--subgidname**. + +Rootless user --userns=Key mappings: + +Key | Host User | Container User +----------|---------------|--------------------- +"" |$UID |0 (Default User account mapped to root user in container.) +keep-id |$UID |$UID (Map user account to same UID within container.) +auto |$UID | nil (Host User UID is not mapped into container.) +nomap |$UID | nil (Host User UID is not mapped into container.) + +Valid _mode_ values are: + +**auto**[:_OPTIONS,..._]: automatically create a unique user namespace. + +The `--userns=auto` flag, requires that the user name `containers` and a range of subordinate user ids that the Podman container is allowed to use be specified in the /etc/subuid and /etc/subgid files. + +Example: `containers:2147483647:2147483648`. + +Podman allocates unique ranges of UIDs and GIDs from the `containers` subordinate user ids. The size of the ranges is based on the number of UIDs required in the image. The number of UIDs and GIDs can be overridden with the `size` option. + +The rootless option `--userns=keep-id` uses all the subuids and subgids of the user. Using `--userns=auto` when starting new containers will not work as long as any containers exist that were started with `--userns=keep-id`. + + Valid `auto` options: + + - *gidmapping*=_CONTAINER_GID:HOST_GID:SIZE_: to force a GID mapping to be present in the user namespace. + - *size*=_SIZE_: to specify an explicit size for the automatic user namespace. e.g. `--userns=auto:size=8192`. If `size` is not specified, `auto` will estimate a size for the user namespace. + - *uidmapping*=_CONTAINER_UID:HOST_UID:SIZE_: to force a UID mapping to be present in the user namespace. + +**container:**_id_: join the user namespace of the specified container. + +**host**: run in the user namespace of the caller. The processes running in the container will have the same privileges on the host as any other process launched by the calling user (default). + +**keep-id**: creates a user namespace where the current rootless user's UID:GID are mapped to the same values in the container. This option is not allowed for containers created by the root user. + + Valid `keep-id` options: + + - *uid*=UID: override the UID inside the container that will be used to map the current rootless user to. + - *gid*=GID: override the GID inside the container that will be used to map the current rootless user to. + +**nomap**: creates a user namespace where the current rootless user's UID:GID are not mapped into the container. This option is not allowed for containers created by the root user. + +**ns:**_namespace_: run the <<container|pod>> in the given existing user namespace. diff --git a/docs/source/markdown/options/userns.pod.md b/docs/source/markdown/options/userns.pod.md new file mode 100644 index 000000000..389f47bd5 --- /dev/null +++ b/docs/source/markdown/options/userns.pod.md @@ -0,0 +1,28 @@ +#### **--userns**=*mode* + +Set the user namespace mode for all the containers in a pod. It defaults to the **PODMAN_USERNS** environment variable. An empty value ("") means user namespaces are disabled. + +Rootless user --userns=Key mappings: + +Key | Host User | Container User +----------|---------------|--------------------- +"" |$UID |0 (Default User account mapped to root user in container.) +keep-id |$UID |$UID (Map user account to same UID within container.) +auto |$UID | nil (Host User UID is not mapped into container.) +nomap |$UID | nil (Host User UID is not mapped into container.) + +Valid _mode_ values are: + + - *auto[:*_OPTIONS,..._*]*: automatically create a namespace. It is possible to specify these options to `auto`: + + - *gidmapping=*_CONTAINER_GID:HOST_GID:SIZE_ to force a GID mapping to be present in the user namespace. + + - *size=*_SIZE_: to specify an explicit size for the automatic user namespace. e.g. `--userns=auto:size=8192`. If `size` is not specified, `auto` will estimate a size for the user namespace. + + - *uidmapping=*_CONTAINER_UID:HOST_UID:SIZE_ to force a UID mapping to be present in the user namespace. + + - *host*: run in the user namespace of the caller. The processes running in the container will have the same privileges on the host as any other process launched by the calling user (default). + + - *keep-id*: creates a user namespace where the current rootless user's UID:GID are mapped to the same values in the container. This option is not allowed for containers created by the root user. + + - *nomap*: creates a user namespace where the current rootless user's UID:GID are not mapped into the container. This option is not allowed for containers created by the root user. diff --git a/docs/source/markdown/options/volume.md b/docs/source/markdown/options/volume.md new file mode 100644 index 000000000..6d0d9a4b3 --- /dev/null +++ b/docs/source/markdown/options/volume.md @@ -0,0 +1,176 @@ +#### **--volume**, **-v**=*[[SOURCE-VOLUME|HOST-DIR:]CONTAINER-DIR[:OPTIONS]]* + +Create a bind mount. If `-v /HOST-DIR:/CONTAINER-DIR` is specified, Podman +bind mounts `/HOST-DIR` in the host to `/CONTAINER-DIR` in the Podman +container. Similarly, `-v SOURCE-VOLUME:/CONTAINER-DIR` will mount the named +volume from the host into the container. If no such named volume exists, Podman will +create one. (Note when using the remote client, including Mac and Windows (excluding WSL2) machines, the volumes will be mounted from the remote server, not necessarily the client machine.) + +The _OPTIONS_ is a comma-separated list and can be: <sup>[[1]](#Footnote1)</sup> + +* **rw**|**ro** +* **z**|**Z** +* [**O**] +* [**U**] +* [**no**]**copy** +* [**no**]**dev** +* [**no**]**exec** +* [**no**]**suid** +* [**r**]**bind** +* [**r**]**shared**|[**r**]**slave**|[**r**]**private**[**r**]**unbindable** + +The `CONTAINER-DIR` must be an absolute path such as `/src/docs`. The volume +will be mounted into the container at this directory. + +Volumes may specify a source as well, as either a directory on the host +or the name of a named volume. If no source is given, the volume will be created as an +anonymously named volume with a randomly generated name, and will be removed when +the <<container|pod>> is removed via the `--rm` flag or the `podman rm --volumes` command. + +If a volume source is specified, it must be a path on the host or the name of a +named volume. Host paths are allowed to be absolute or relative; relative paths +are resolved relative to the directory Podman is run in. If the source does not +exist, Podman will return an error. Users must pre-create the source files or +directories. + +Any source that does not begin with a `.` or `/` will be treated as the name of +a named volume. If a volume with that name does not exist, it will be created. +Volumes created with names are not anonymous, and they are not removed by the `--rm` +option and the `podman rm --volumes` command. + +Specify multiple **-v** options to mount one or more volumes into a +<<container|pod>>. + + `Write Protected Volume Mounts` + +Add **:ro** or **:rw** option to mount a volume in read-only or +read-write mode, respectively. By default, the volumes are mounted read-write. +See examples. + + `Chowning Volume Mounts` + +By default, Podman does not change the owner and group of source volume +directories mounted into containers. If a <<container|pod>> is created in a new user +namespace, the UID and GID in the container may correspond to another UID and +GID on the host. + +The `:U` suffix tells Podman to use the correct host UID and GID based on the +UID and GID within the <<container|pod>>, to change recursively the owner and group of +the source volume. + +**Warning** use with caution since this will modify the host filesystem. + + `Labeling Volume Mounts` + +Labeling systems like SELinux require that proper labels are placed on volume +content mounted into a <<container|pod>>. Without a label, the security system might +prevent the processes running inside the <<container|pod>> from using the content. By +default, Podman does not change the labels set by the OS. + +To change a label in the <<container|pod>> context, add either of two suffixes +**:z** or **:Z** to the volume mount. These suffixes tell Podman to relabel file +objects on the shared volumes. The **z** option tells Podman that two <<containers|pods>> +share the volume content. As a result, Podman labels the content with a shared +content label. Shared volume labels allow all containers to read/write content. +The **Z** option tells Podman to label the content with a private unshared label. +Only the current <<container|pod>> can use a private volume. + +Note: Do not relabel system files and directories. Relabeling system content +might cause other confined services on your machine to fail. For these types +of containers we recommend disabling SELinux separation. The option +**--security-opt label=disable** disables SELinux separation for the <<container|pod>>. +For example if a user wanted to volume mount their entire home directory into a +<<container|pod>>, they need to disable SELinux separation. + + $ podman <<fullsubcommand>> --security-opt label=disable -v $HOME:/home/user fedora touch /home/user/file + + `Overlay Volume Mounts` + + The `:O` flag tells Podman to mount the directory from the host as a +temporary storage using the `overlay file system`. The <<container|pod>> processes +can modify content within the mountpoint which is stored in the +container storage in a separate directory. In overlay terms, the source +directory will be the lower, and the container storage directory will be the +upper. Modifications to the mount point are destroyed when the <<container|pod>> +finishes executing, similar to a tmpfs mount point being unmounted. + +For advanced users, the **overlay** option also supports custom non-volatile +**upperdir** and **workdir** for the overlay mount. Custom **upperdir** and +**workdir** can be fully managed by the users themselves, and Podman will not +remove it on lifecycle completion. +Example **:O,upperdir=/some/upper,workdir=/some/work** + + Subsequent executions of the container will see the original source directory +content, any changes from previous <<container|pod>> executions no longer exist. + + One use case of the overlay mount is sharing the package cache from the +host into the container to allow speeding up builds. + + Note: + + - The `O` flag conflicts with other options listed above. +Content mounted into the container is labeled with the private label. + On SELinux systems, labels in the source directory must be readable +by the <<|pod infra>> container label. Usually containers can read/execute `container_share_t` +and can read/write `container_file_t`. If unable to change the labels on a +source volume, SELinux container separation must be disabled for the <<|pod or infra>> container +to work. + - The source directory mounted into the <<container|pod>> with an overlay mount +should not be modified, it can cause unexpected failures. It is recommended +to not modify the directory until the container finishes running. + + `Mounts propagation` + +By default bind mounted volumes are `private`. That means any mounts done +inside the <<container|pod>> will not be visible on host and vice versa. One can change +this behavior by specifying a volume mount propagation property. Making a +volume shared mounts done under that volume inside the <<container|pod>> will be +visible on host and vice versa. Making a volume **slave** enables only one +way mount propagation and that is mounts done on host under that volume +will be visible inside container but not the other way around. <sup>[[1]](#Footnote1)</sup> + +To control mount propagation property of a volume one can use the [**r**]**shared**, +[**r**]**slave**, [**r**]**private** or the [**r**]**unbindable** propagation flag. +Propagation property can be specified only for bind mounted volumes and not for +internal volumes or named volumes. For mount propagation to work the source mount +point (the mount point where source dir is mounted on) has to have the right propagation +properties. For shared volumes, the source mount point has to be shared. And for +slave volumes, the source mount point has to be either shared or slave. +<sup>[[1]](#Footnote1)</sup> + +To recursively mount a volume and all of its submounts into a +<<container|pod>>, use the **rbind** option. By default the bind option is +used, and submounts of the source directory will not be mounted into the +<<container|pod>>. + +Mounting the volume with the **nosuid** options means that SUID applications on +the volume will not be able to change their privilege. By default volumes +are mounted with **nosuid**. + +Mounting the volume with the **noexec** option means that no executables on the +volume will be able to be executed within the <<container|pod>>. + +Mounting the volume with the **nodev** option means that no devices on the volume +will be able to be used by processes within the <<container|pod>>. By default volumes +are mounted with **nodev**. + +If the _HOST-DIR_ is a mount point, then **dev**, **suid**, and **exec** options are +ignored by the kernel. + +Use **df HOST-DIR** to figure out the source mount, then use +**findmnt -o TARGET,PROPAGATION _source-mount-dir_** to figure out propagation +properties of source mount. If **findmnt**(1) utility is not available, then one +can look at the mount entry for the source mount point in _/proc/self/mountinfo_. Look +at the "optional fields" and see if any propagation properties are specified. +In there, **shared:N** means the mount is shared, **master:N** means mount +is slave, and if nothing is there, the mount is private. <sup>[[1]](#Footnote1)</sup> + +To change propagation properties of a mount point, use **mount**(8) command. For +example, if one wants to bind mount source directory _/foo_, one can do +**mount --bind /foo /foo** and **mount --make-private --make-shared /foo**. This +will convert /foo into a shared mount point. Alternatively, one can directly +change propagation properties of source mount. Say _/_ is source mount for +_/foo_, then use **mount --make-shared /** to convert _/_ into a shared mount. + +Note: if the user only has access rights via a group, accessing the volume +from inside a rootless <<container|pod>> will fail. |