Add daemon documentation on user namespaces feature
Remove the experimental docs for user namespaces and add similar content to the `docker daemon` command documentation. Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
This commit is contained in:
Phil Estes
Tibor Vass
Родитель
b5843f62f8
Коммит
36960be45f
|
|
@ -62,6 +62,7 @@ weight = -1
|
|||
--tlscert="~/.docker/cert.pem" Path to TLS certificate file
|
||||
--tlskey="~/.docker/key.pem" Path to TLS key file
|
||||
--tlsverify Use TLS and verify the remote
|
||||
--userns-remap="default" Enable user namespace remapping
|
||||
--userland-proxy=true Use userland proxy for loopback traffic
|
||||
|
||||
Options with [] may be specified multiple times.
|
||||
|
|
@ -632,6 +633,133 @@ For information about how to create an authorization plugin, see [authorization
|
|||
plugin](../../extend/authorization.md) section in the Docker extend section of this documentation.
|
||||
|
||||
|
||||
## Daemon user namespace options
|
||||
|
||||
The Linux kernel [user namespace support](http://man7.org/linux/man-pages/man7/user_namespaces.7.html) provides additional security by enabling
|
||||
a process, and therefore a container, to have a unique range of user and
|
||||
group IDs which are outside the traditional user and group range utilized by
|
||||
the host system. Potentially the most important security improvement is that,
|
||||
by default, container processes running as the `root` user will have expected
|
||||
administrative privilege (with some restrictions) inside the container but will
|
||||
effectively be mapped to an unprivileged `uid` on the host.
|
||||
|
||||
When user namespace support is enabled, Docker creates a single daemon-wide mapping
|
||||
for all containers running on the same engine instance. The mappings will
|
||||
utilize the existing subordinate user and group ID feature available on all modern
|
||||
Linux distributions.
|
||||
The [`/etc/subuid`](http://man7.org/linux/man-pages/man5/subuid.5.html) and
|
||||
[`/etc/subgid`](http://man7.org/linux/man-pages/man5/subgid.5.html) files will be
|
||||
read for the user, and optional group, specified to the `--userns-remap`
|
||||
parameter. If you do not wish to specify your own user and/or group, you can
|
||||
provide `default` as the value to this flag, and a user will be created on your behalf
|
||||
and provided subordinate uid and gid ranges. This default user will be named
|
||||
`dockremap`, and entries will be created for it in `/etc/passwd` and
|
||||
`/etc/group` using your distro's standard user and group creation tools.
|
||||
|
||||
> **Note**: The single mapping per-daemon restriction is in place for now
|
||||
> because Docker shares image layers from its local cache across all
|
||||
> containers running on the engine instance. Since file ownership must be
|
||||
> the same for all containers sharing the same layer content, the decision
|
||||
> was made to map the file ownership on `docker pull` to the daemon's user and
|
||||
> group mappings so that there is no delay for running containers once the
|
||||
> content is downloaded. This design preserves the same performance for `docker
|
||||
> pull`, `docker push`, and container startup as users expect with
|
||||
> user namespaces disabled.
|
||||
|
||||
### Starting the daemon with user namespaces enabled
|
||||
|
||||
To enable user namespace support, start the daemon with the
|
||||
`--userns-remap` flag, which accepts values in the following formats:
|
||||
|
||||
- uid
|
||||
- uid:gid
|
||||
- username
|
||||
- username:groupname
|
||||
|
||||
If numeric IDs are provided, translation back to valid user or group names
|
||||
will occur so that the subordinate uid and gid information can be read, given
|
||||
these resources are name-based, not id-based. If the numeric ID information
|
||||
provided does not exist as entries in `/etc/passwd` or `/etc/group`, daemon
|
||||
startup will fail with an error message.
|
||||
|
||||
*Example: starting with default Docker user management:*
|
||||
|
||||
```
|
||||
$ docker daemon --userns-remap=default
|
||||
```
|
||||
When `default` is provided, Docker will create - or find the existing - user and group
|
||||
named `dockremap`. If the user is created, and the Linux distribution has
|
||||
appropriate support, the `/etc/subuid` and `/etc/subgid` files will be populated
|
||||
with a contiguous 65536 length range of subordinate user and group IDs, starting
|
||||
at an offset based on prior entries in those files. For example, Ubuntu will
|
||||
create the following range, based on an existing user named `user1` already owning
|
||||
the first 65536 range:
|
||||
|
||||
```
|
||||
$ cat /etc/subuid
|
||||
user1:100000:65536
|
||||
dockremap:165536:65536
|
||||
```
|
||||
|
||||
> **Note:** On a fresh Fedora install, we had to `touch` the
|
||||
> `/etc/subuid` and `/etc/subgid` files to have ranges assigned when users
|
||||
> were created. Once these files existed, range assignment on user creation
|
||||
> worked properly.
|
||||
|
||||
If you have a preferred/self-managed user with subordinate ID mappings already
|
||||
configured, you can provide that username or uid to the `--userns-remap` flag.
|
||||
If you have a group that doesn't match the username, you may provide the `gid`
|
||||
or group name as well; otherwise the username will be used as the group name
|
||||
when querying the system for the subordinate group ID range.
|
||||
|
||||
### Detailed information on `subuid`/`subgid` ranges
|
||||
|
||||
Given potential advanced use of the subordinate ID ranges by power users, the
|
||||
following paragraphs define how the Docker daemon currently uses the range entries
|
||||
found within the subordinate range files.
|
||||
|
||||
The simplest case is that only one contiguous range is defined for the
|
||||
provided user or group. In this case, Docker will use that entire contiguous
|
||||
range for the mapping of host uids and gids to the container process. This
|
||||
means that the first ID in the range will be the remapped root user, and the
|
||||
IDs above that initial ID will map host ID 1 through the end of the range.
|
||||
|
||||
From the example `/etc/subid` content shown above, the remapped root
|
||||
user would be uid 165536.
|
||||
|
||||
If the system administrator has set up multiple ranges for a single user or
|
||||
group, the Docker daemon will read all the available ranges and use the
|
||||
following algorithm to create the mapping ranges:
|
||||
|
||||
1. The range segments found for the particular user will be sorted by *start ID* ascending.
|
||||
2. Map segments will be created from each range in increasing value with a length matching the length of each segment. Therefore the range segment with the lowest numeric starting value will be equal to the remapped root, and continue up through host uid/gid equal to the range segment length. As an example, if the lowest segment starts at ID 1000 and has a length of 100, then a map of 1000 -> 0 (the remapped root) up through 1100 -> 100 will be created from this segment. If the next segment starts at ID 10000, then the next map will start with mapping 10000 -> 101 up to the length of this second segment. This will continue until no more segments are found in the subordinate files for this user.
|
||||
3. If more than five range segments exist for a single user, only the first five will be utilized, matching the kernel's limitation of only five entries in `/proc/self/uid_map` and `proc/self/gid_map`.
|
||||
|
||||
### User namespace known restrictions
|
||||
|
||||
The following standard Docker features are currently incompatible when
|
||||
running a Docker daemon with user namespaces enabled:
|
||||
|
||||
- sharing PID or NET namespaces with the host (`--pid=host` or `--net=host`)
|
||||
- sharing a network namespace with an existing container (`--net=container:*other*`)
|
||||
- sharing an IPC namespace with an existing container (`--ipc=container:*other*`)
|
||||
- A `--readonly` container filesystem (this is a Linux kernel restriction against remounting with modified flags of a currently mounted filesystem when inside a user namespace)
|
||||
- external (volume or graph) drivers which are unaware/incapable of using daemon user mappings
|
||||
- Using `--privileged` mode flag on `docker run`
|
||||
|
||||
In general, user namespaces are an advanced feature and will require
|
||||
coordination with other capabilities. For example, if volumes are mounted from
|
||||
the host, file ownership will have to be pre-arranged if the user or
|
||||
administrator wishes the containers to have expected access to the volume
|
||||
contents.
|
||||
|
||||
Finally, while the `root` user inside a user namespaced container process has
|
||||
many of the expected admin privileges that go along with being the superuser, the
|
||||
Linux kernel has restrictions based on internal knowledge that this is a user namespaced
|
||||
process. The most notable restriction that we are aware of at this time is the
|
||||
inability to use `mknod`. Permission will be denied for device creation even as
|
||||
container `root` inside a user namespace.
|
||||
|
||||
## Miscellaneous options
|
||||
|
||||
IP masquerading uses address translation to allow containers without a public
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@ to build a Docker binary with the experimental features enabled:
|
|||
## Current experimental features
|
||||
|
||||
* [External graphdriver plugins](plugins_graphdriver.md)
|
||||
* [User namespaces](userns.md)
|
||||
* The user namespaces feature has graduated from experimental.
|
||||
|
||||
## How to comment on an experimental feature
|
||||
|
||||
|
|
|
|||
|
|
@ -1,119 +0,0 @@
|
|||
# Experimental: User namespace support
|
||||
|
||||
Linux kernel [user namespace support](http://man7.org/linux/man-pages/man7/user_namespaces.7.html) provides additional security by enabling
|
||||
a process--and therefore a container--to have a unique range of user and
|
||||
group IDs which are outside the traditional user and group range utilized by
|
||||
the host system. Potentially the most important security improvement is that,
|
||||
by default, container processes running as the `root` user will have expected
|
||||
administrative privilege (with some restrictions) inside the container but will
|
||||
effectively be mapped to an unprivileged `uid` on the host.
|
||||
|
||||
In this experimental phase, the Docker daemon creates a single daemon-wide mapping
|
||||
for all containers running on the same engine instance. The mappings will
|
||||
utilize the existing subordinate user and group ID feature available on all modern
|
||||
Linux distributions.
|
||||
The [`/etc/subuid`](http://man7.org/linux/man-pages/man5/subuid.5.html) and
|
||||
[`/etc/subgid`](http://man7.org/linux/man-pages/man5/subgid.5.html) files will be
|
||||
read for the user, and optional group, specified to the `--userns-remap`
|
||||
parameter. If you do not wish to specify your own user and/or group, you can
|
||||
provide `default` as the value to this flag, and a user will be created on your behalf
|
||||
and provided subordinate uid and gid ranges. This default user will be named
|
||||
`dockremap`, and entries will be created for it in `/etc/passwd` and
|
||||
`/etc/group` using your distro's standard user and group creation tools.
|
||||
|
||||
> **Note**: The single mapping per-daemon restriction exists for this experimental
|
||||
> phase because Docker shares image layers from its local cache across all
|
||||
> containers running on the engine instance. Since file ownership must be
|
||||
> the same for all containers sharing the same layer content, the decision
|
||||
> was made to map the file ownership on `docker pull` to the daemon's user and
|
||||
> group mappings so that there is no delay for running containers once the
|
||||
> content is downloaded--exactly the same performance characteristics as with
|
||||
> user namespaces disabled.
|
||||
|
||||
## Starting the daemon with user namespaces enabled
|
||||
To enable this experimental user namespace support for a Docker daemon instance,
|
||||
start the daemon with the aforementioned `--userns-remap` flag, which accepts
|
||||
values in the following formats:
|
||||
|
||||
- uid
|
||||
- uid:gid
|
||||
- username
|
||||
- username:groupname
|
||||
|
||||
If numeric IDs are provided, translation back to valid user or group names
|
||||
will occur so that the subordinate uid and gid information can be read, given
|
||||
these resources are name-based, not id-based. If the numeric ID information
|
||||
provided does not exist as entries in `/etc/passwd` or `/etc/group`, daemon
|
||||
startup will fail with an error message.
|
||||
|
||||
*An example: starting with default Docker user management:*
|
||||
|
||||
```
|
||||
$ docker daemon --userns-remap=default
|
||||
```
|
||||
In this case, Docker will create--or find the existing--user and group
|
||||
named `dockremap`. If the user is created, and the Linux distribution has
|
||||
appropriate support, the `/etc/subuid` and `/etc/subgid` files will be populated
|
||||
with a contiguous 65536 length range of subordinate user and group IDs, starting
|
||||
at an offset based on prior entries in those files. For example, Ubuntu will
|
||||
create the following range, based on an existing user already having the first
|
||||
65536 range:
|
||||
|
||||
```
|
||||
$ cat /etc/subuid
|
||||
user1:100000:65536
|
||||
dockremap:165536:65536
|
||||
```
|
||||
|
||||
> **Note:** On a fresh Fedora install, we found that we had to `touch` the
|
||||
> `/etc/subuid` and `/etc/subgid` files to have ranges assigned when users
|
||||
> were created. Once these files existed, range assignment on user creation
|
||||
> worked properly.
|
||||
|
||||
If you have a preferred/self-managed user with subordinate ID mappings already
|
||||
configured, you can provide that username or uid to the `--userns-remap` flag.
|
||||
If you have a group that doesn't match the username, you may provide the `gid`
|
||||
or group name as well; otherwise the username will be used as the group name
|
||||
when querying the system for the subordinate group ID range.
|
||||
|
||||
## Detailed information on `subuid`/`subgid` ranges
|
||||
|
||||
Given there may be advanced use of the subordinate ID ranges by power users, we will
|
||||
describe how the Docker daemon uses the range entries within these files under the
|
||||
current experimental user namespace support.
|
||||
|
||||
The simplest case exists where only one contiguous range is defined for the
|
||||
provided user or group. In this case, Docker will use that entire contiguous
|
||||
range for the mapping of host uids and gids to the container process. This
|
||||
means that the first ID in the range will be the remapped root user, and the
|
||||
IDs above that initial ID will map host ID 1 through the end of the range.
|
||||
|
||||
From the example `/etc/subid` content shown above, that means the remapped root
|
||||
user would be uid 165536.
|
||||
|
||||
If the system administrator has set up multiple ranges for a single user or
|
||||
group, the Docker daemon will read all the available ranges and use the
|
||||
following algorithm to create the mapping ranges:
|
||||
|
||||
1. The ranges will be sorted by *start ID* ascending
|
||||
2. Maps will be created from each range with where the host ID will increment starting at 0 for the first range, 0+*range1* length for the second, and so on. This means that the lowest range start ID will be the remapped root, and all further ranges will map IDs from 1 through the uid or gid that equals the sum of all range lengths.
|
||||
3. Ranges segments above five will be ignored as the kernel ignores any ID maps after five (in `/proc/self/{u,g}id_map`)
|
||||
|
||||
## User namespace known restrictions
|
||||
|
||||
The following standard Docker features are currently incompatible when
|
||||
running a Docker daemon with experimental user namespaces enabled:
|
||||
|
||||
- sharing namespaces with the host (--pid=host, --net=host, etc.)
|
||||
- sharing namespaces with other containers (--net=container:*other*)
|
||||
- A `--readonly` container filesystem (a Linux kernel restriction on remount with new flags of a currently mounted filesystem when inside a user namespace)
|
||||
- external (volume/graph) drivers which are unaware/incapable of using daemon user mappings
|
||||
- Using `--privileged` mode containers
|
||||
- volume use without pre-arranging proper file ownership in mounted volumes
|
||||
|
||||
Additionally, while the `root` user inside a user namespaced container
|
||||
process has many of the privileges of the administrative root user, the
|
||||
following operations will fail:
|
||||
|
||||
- Use of `mknod` - permission is denied for device creation by the container root
|
||||
- others will be listed here when fully tested
|
||||
|
|
@ -53,6 +53,7 @@ docker-daemon - Enable daemon mode
|
|||
[**--tlskey**[=*~/.docker/key.pem*]]
|
||||
[**--tlsverify**]
|
||||
[**--userland-proxy**[=*true*]]
|
||||
[**--userns-remap**[=*default*]]
|
||||
|
||||
# DESCRIPTION
|
||||
**docker** has two distinct functions. It is used for starting the Docker
|
||||
|
|
@ -223,6 +224,9 @@ unix://[/path/to/socket] to use.
|
|||
**--userland-proxy**=*true*|*false*
|
||||
Rely on a userland proxy implementation for inter-container and outside-to-container loopback communications. Default is true.
|
||||
|
||||
**--userns-remap**=*default*|*uid:gid*|*user:group*|*user*|*uid*
|
||||
Enable user namespaces for containers on the daemon. Specifying "default" will cause a new user and group to be created to handle UID and GID range remapping for the user namespace mappings used for contained processes. Specifying a user (or uid) and optionally a group (or gid) will cause the daemon to lookup the user and group's subordinate ID ranges for use as the user namespace mappings for contained processes.
|
||||
|
||||
# STORAGE DRIVER OPTIONS
|
||||
|
||||
Docker uses storage backends (known as "graphdrivers" in the Docker
|
||||
|
|
|
|||
Загрузка…
Ссылка в новой задаче