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Diffstat (limited to 'docs/source/markdown/podman-run.1.md')
| -rw-r--r-- | docs/source/markdown/podman-run.1.md | 74 |
1 files changed, 61 insertions, 13 deletions
diff --git a/docs/source/markdown/podman-run.1.md b/docs/source/markdown/podman-run.1.md index f84a5913c..e149c8531 100644 --- a/docs/source/markdown/podman-run.1.md +++ b/docs/source/markdown/podman-run.1.md @@ -1047,23 +1047,71 @@ Remote connections use local containers.conf for defaults Set the umask inside the container. Defaults to `0022`. Remote connections use local containers.conf for defaults -#### **\-\-uidmap**=*container_uid*:*host_uid*:*amount* +#### **\-\-uidmap**=*container_uid*:*from_uid*:*amount* -Run the container in a new user namespace using the supplied mapping. This option conflicts -with the **\-\-userns** and **\-\-subuidname** flags. -This option can be passed several times to map different ranges. If calling **podman run** -as an unprivileged user, the user needs to have the right to use the mapping. See **subuid**(5). +Run the container in a new user namespace using the supplied mapping. This +option conflicts with the **\-\-userns** and **\-\-subuidname** options. This +option provides a way to map host UIDs to container UIDs. It can be passed +several times to map different ranges. -The following example maps uids 0-1999 in the container to the uids 30000-31999 on the host: **\-\-uidmap=0:30000:2000**. +The _from_uid_ value is based upon the user running the command, either rootful or rootless users. +* rootful user: *container_uid*:*host_uid*:*amount* +* rootless user: *container_uid*:*intermediate_uid*:*amount* -**Important note:** The new user namespace mapping based on **\-\-uidmap** is based on the initial mapping made in the _/etc/subuid_ file. -Assuming there is a _/etc/subuid_ mapping **username:100000:65536**, then **username** is initially mapped to a namespace starting with -uid **100000** for **65536** ids. From here the **\-\-uidmap** mapping to the new namespace starts from **0** again, but is based on the initial mapping. -Meaning **username** is initially mapped to uid **100000** which is referenced as **0** in the following **\-\-uidmap** mapping. In terms of the example -above: The user **username** is mapped to user **100000** of the initial namespace then the -**30000**st id of this namespace (which is uid 130000 in this namespace) is mapped to container namespace user id **0**. (username -> 100000 / 30000 -> 0) +When **podman run** is called by a privileged user, the option **\-\-uidmap** +works as a direct mapping between host UIDs and container UIDs. -_Note_: A minimal mapping has to have at least container uid **0** mapped to the parent user namespace. +host UID -> container UID + +The _amount_ specifies the number of consecutive UIDs that will be mapped. +If for example _amount_ is **4** the mapping would look like: + +| host UID | container UID | +| - | - | +| _from_uid_ | _container_uid_ | +| _from_uid_ + 1 | _container_uid_ + 1 | +| _from_uid_ + 2 | _container_uid_ + 2 | +| _from_uid_ + 3 | _container_uid_ + 3 | + +When **podman run** is called by an unprivileged user (i.e. running rootless), +the value _from_uid_ is interpreted as an "intermediate UID". In the rootless +case, host UIDs are not mapped directly to container UIDs. Instead the mapping +happens over two mapping steps: + +host UID -> intermediate UID -> container UID + +The **\-\-uidmap** option only influences the second mapping step. + +The first mapping step is derived by Podman from the contents of the file +_/etc/subuid_ and the UID of the user calling Podman. + +First mapping step: +| host UID | intermediate UID | +| - | - | +| UID for the user starting Podman | 0 | +| 1st subordinate UID for the user starting Podman | 1 | +| 2nd subordinate UID for the user starting Podman | 2 | +| 3rd subordinate UID for the user starting Podman | 3 | +| nth subordinate UID for the user starting Podman | n | + +To be able to use intermediate UIDs greater than zero, the user needs to have +subordinate UIDs configured in _/etc/subuid_. See **subuid**(5). + +The second mapping step is configured with **\-\-uidmap**. + +If for example _amount_ is **5** the second mapping step would look like: + +| intermediate UID | container UID | +| - | - | +| _from_uid_ | _container_uid_ | +| _from_uid_ + 1 | _container_uid_ + 1 | +| _from_uid_ + 2 | _container_uid_ + 2 | +| _from_uid_ + 3 | _container_uid_ + 3 | +| _from_uid_ + 4 | _container_uid_ + 4 | + +Even if a user does not have any subordinate UIDs in _/etc/subuid_, +**\-\-uidmap** could still be used to map the normal UID of the user to a +container UID by running `podman run --uidmap $container_uid:0:1 --user $container_uid ...`. #### **\-\-ulimit**=*option* |