github.com/containers/podman/v5@v5.1.0-rc1/docs/source/markdown/options/volume.md (about)

     1  ####> This option file is used in:
     2  ####>   podman create, pod clone, pod create, run
     3  ####> If file is edited, make sure the changes
     4  ####> are applicable to all of those.
     5  #### **--volume**, **-v**=*[[SOURCE-VOLUME|HOST-DIR:]CONTAINER-DIR[:OPTIONS]]*
     6  
     7  Create a bind mount. If `-v /HOST-DIR:/CONTAINER-DIR` is specified, Podman
     8  bind mounts `/HOST-DIR` from the host into `/CONTAINER-DIR` in the Podman
     9  container. Similarly, `-v SOURCE-VOLUME:/CONTAINER-DIR` mounts the named
    10  volume from the host into the container. If no such named volume exists,
    11  Podman creates one. If no source is given, the volume is created
    12  as an anonymously named volume with a randomly generated name, and is
    13  removed when the <<container|pod>> is removed via the `--rm` flag or
    14  the `podman rm --volumes` command.
    15  
    16  (Note when using the remote client, including Mac and Windows (excluding WSL2) machines, the volumes are mounted from the remote server, not necessarily the client machine.)
    17  
    18  The _OPTIONS_ is a comma-separated list and can be one or more of:
    19  
    20  * **rw**|**ro**
    21  * **z**|**Z**
    22  * [**O**]
    23  * [**U**]
    24  * [**no**]**copy**
    25  * [**no**]**dev**
    26  * [**no**]**exec**
    27  * [**no**]**suid**
    28  * [**r**]**bind**
    29  * [**r**]**shared**|[**r**]**slave**|[**r**]**private**[**r**]**unbindable** <sup>[[1]](#Footnote1)</sup>
    30  * **idmap**[=**options**]
    31  
    32  The `CONTAINER-DIR` must be an absolute path such as `/src/docs`. The volume
    33  is mounted into the container at this directory.
    34  
    35  If a volume source is specified, it must be a path on the host or the name of a
    36  named volume. Host paths are allowed to be absolute or relative; relative paths
    37  are resolved relative to the directory Podman is run in. If the source does not
    38  exist, Podman returns an error. Users must pre-create the source files or
    39  directories.
    40  
    41  Any source that does not begin with a `.` or `/` is treated as the name of
    42  a named volume. If a volume with that name does not exist, it is created.
    43  Volumes created with names are not anonymous, and they are not removed by the `--rm`
    44  option and the `podman rm --volumes` command.
    45  
    46  Specify multiple **-v** options to mount one or more volumes into a
    47  <<container|pod>>.
    48  
    49  `Write Protected Volume Mounts`
    50  
    51  Add **:ro** or **:rw** option to mount a volume in read-only or
    52  read-write mode, respectively. By default, the volumes are mounted read-write.
    53  See examples.
    54  
    55  `Chowning Volume Mounts`
    56  
    57  By default, Podman does not change the owner and group of source volume
    58  directories mounted into containers. If a <<container|pod>> is created in a new
    59  user namespace, the UID and GID in the container may correspond to another UID
    60  and GID on the host.
    61  
    62  The `:U` suffix tells Podman to use the correct host UID and GID based on the
    63  UID and GID within the <<container|pod>>, to change recursively the owner and
    64  group of the source volume. Chowning walks the file system under the volume and
    65  changes the UID/GID on each file. If the volume has thousands of inodes, this
    66  process takes a long time, delaying the start of the <<container|pod>>.
    67  
    68  **Warning** use with caution since this modifies the host filesystem.
    69  
    70  `Labeling Volume Mounts`
    71  
    72  Labeling systems like SELinux require that proper labels are placed on volume
    73  content mounted into a <<container|pod>>. Without a label, the security system
    74  might prevent the processes running inside the <<container|pod>> from using the
    75  content. By default, Podman does not change the labels set by the OS.
    76  
    77  To change a label in the <<container|pod>> context, add either of two suffixes
    78  **:z** or **:Z** to the volume mount. These suffixes tell Podman to relabel file
    79  objects on the shared volumes. The **z** option tells Podman that two or more
    80  <<containers|pods>> share the volume content. As a result, Podman labels the
    81  content with a shared content label. Shared volume labels allow all containers
    82  to read/write content. The **Z** option tells Podman to label the content with
    83  a private unshared label Only the current <<container|pod>> can use a private
    84  volume. Relabeling walks the file system under the volume and changes the label
    85  on each file, if the volume has thousands of inodes, this process takes a
    86  long time, delaying the start of the <<container|pod>>. If the volume
    87  was previously relabeled with the `z` option, Podman is optimized to not relabel
    88  a second time. If files are moved into the volume, then the labels can be
    89  manually change with the `chcon -Rt container_file_t PATH` command.
    90  
    91  Note: Do not relabel system files and directories. Relabeling system content
    92  might cause other confined services on the machine to fail.  For these types
    93  of containers we recommend disabling SELinux separation.  The option
    94  **--security-opt label=disable** disables SELinux separation for the <<container|pod>>.
    95  For example if a user wanted to volume mount their entire home directory into a
    96  <<container|pod>>, they need to disable SELinux separation.
    97  
    98      $ podman <<fullsubcommand>> --security-opt label=disable -v $HOME:/home/user fedora touch /home/user/file
    99  
   100  `Overlay Volume Mounts`
   101  
   102  The `:O` flag tells Podman to mount the directory from the host as a
   103  temporary storage using the `overlay file system`. The <<container|pod>> processes
   104  can modify content within the mountpoint which is stored in the
   105  container storage in a separate directory. In overlay terms, the source
   106  directory is the lower, and the container storage directory is the
   107  upper. Modifications to the mount point are destroyed when the <<container|pod>>
   108  finishes executing, similar to a tmpfs mount point being unmounted.
   109  
   110  For advanced users, the **overlay** option also supports custom non-volatile
   111  **upperdir** and **workdir** for the overlay mount. Custom **upperdir** and
   112  **workdir** can be fully managed by the users themselves, and Podman does not
   113  remove it on lifecycle completion.
   114  Example **:O,upperdir=/some/upper,workdir=/some/work**
   115  
   116  Subsequent executions of the container sees the original source directory
   117  content, any changes from previous <<container|pod>> executions no longer exist.
   118  
   119  One use case of the overlay mount is sharing the package cache from the
   120  host into the container to allow speeding up builds.
   121  
   122  Note: The `O` flag conflicts with other options listed above.
   123  
   124  Content mounted into the container is labeled with the private label.
   125  On SELinux systems, labels in the source directory must be readable
   126  by the <<|pod infra>> container label. Usually containers can read/execute `container_share_t`
   127  and can read/write `container_file_t`. If unable to change the labels on a
   128  source volume, SELinux container separation must be disabled for the <<|pod or infra>> container
   129  to work.
   130  
   131  Do not modify the source directory mounted into the <<container|pod>> with an overlay mount,
   132  it can cause unexpected failures. Only modify the directory after the container finishes running.
   133  
   134  `Mounts propagation`
   135  
   136  By default, bind-mounted volumes are `private`. That means any mounts done
   137  inside the <<container|pod>> are not visible on the host and vice versa.
   138  One can change this behavior by specifying a volume mount propagation property.
   139  When a volume is `shared`, mounts done under that volume inside the <<container|pod>>
   140  are visible on host and vice versa. Making a volume **slave**<sup>[[1]](#Footnote1)</sup>
   141  enables only one-way mount propagation: mounts done on the host under that volume
   142  are visible inside the container but not the other way around.
   143  
   144  To control mount propagation property of a volume one can use the [**r**]**shared**,
   145  [**r**]**slave**, [**r**]**private** or the [**r**]**unbindable** propagation flag.
   146  Propagation property can be specified only for bind mounted volumes and not for
   147  internal volumes or named volumes. For mount propagation to work the source mount
   148  point (the mount point where source dir is mounted on) has to have the right propagation
   149  properties. For shared volumes, the source mount point has to be shared. And for
   150  slave volumes, the source mount point has to be either shared or slave.
   151  <sup>[[1]](#Footnote1)</sup>
   152  
   153  To recursively mount a volume and all of its submounts into a
   154  <<container|pod>>, use the **rbind** option. By default the bind option is
   155  used, and submounts of the source directory is not mounted into the
   156  <<container|pod>>.
   157  
   158  Mounting the volume with a **copy** option tells podman to copy content from
   159  the underlying destination directory onto newly created internal volumes. The
   160  **copy** only happens on the initial creation of the volume. Content is not
   161  copied up when the volume is subsequently used on different containers. The
   162  **copy** option is ignored on bind mounts and has no effect.
   163  
   164  Mounting volumes with the **nosuid** options means that SUID executables on the
   165  volume can not be used by applications to change their privilege. By default
   166  volumes are mounted with **nosuid**.
   167  
   168  Mounting the volume with the **noexec** option means that no executables on the
   169  volume can be executed within the <<container|pod>>.
   170  
   171  Mounting the volume with the **nodev** option means that no devices on the volume
   172  can be used by processes within the <<container|pod>>. By default volumes
   173  are mounted with **nodev**.
   174  
   175  If the _HOST-DIR_ is a mount point, then **dev**, **suid**, and **exec** options are
   176  ignored by the kernel.
   177  
   178  Use **df HOST-DIR** to figure out the source mount, then use
   179  **findmnt -o TARGET,PROPAGATION _source-mount-dir_** to figure out propagation
   180  properties of source mount. If **findmnt**(1) utility is not available, then one
   181  can look at the mount entry for the source mount point in _/proc/self/mountinfo_. Look
   182  at the "optional fields" and see if any propagation properties are specified.
   183  In there, **shared:N** means the mount is shared, **master:N** means mount
   184  is slave, and if nothing is there, the mount is private. <sup>[[1]](#Footnote1)</sup>
   185  
   186  To change propagation properties of a mount point, use **mount**(8) command. For
   187  example, if one wants to bind mount source directory _/foo_, one can do
   188  **mount --bind /foo /foo** and **mount --make-private --make-shared /foo**. This
   189  converts /foo into a shared mount point. Alternatively, one can directly
   190  change propagation properties of source mount. Say _/_ is source mount for
   191  _/foo_, then use **mount --make-shared /** to convert _/_ into a shared mount.
   192  
   193  Note: if the user only has access rights via a group, accessing the volume
   194  from inside a rootless <<container|pod>> fails.
   195  
   196  `Idmapped mount`
   197  
   198  If `idmap` is specified, create an idmapped mount to the target user
   199  namespace in the container. The idmap option supports a custom mapping
   200  that can be different than the user namespace used by the
   201  container. The mapping can be specified after the idmap option like:
   202  `idmap=uids=0-1-10#10-11-10;gids=0-100-10`.
   203  For each triplet, the first value is the start of the backing file
   204  system IDs that are mapped to the second value on the host.  The
   205  length of this mapping is given in the third value.
   206  Multiple ranges are separated with #.