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update centos systemd documentation

This commit is contained in:
Jim Perrin 2016-01-04 14:00:30 -06:00
parent b262633e7b
commit 3536c1e8be
2 changed files with 12 additions and 16 deletions
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14
centos/README.md
View File

@ -42,7 +42,7 @@ By default, the CentOS containers are built using yum's `nodocs` option, which h
# Systemd integration
Currently, systemd in CentOS 7 has been removed and replaced with a `fakesystemd` package for dependency resolution. This is due to systemd requiring the `CAP_SYS_ADMIN` capability, as well as being able to read the host's cgroups. If you wish to replace the fakesystemd package and use systemd normally, please follow the steps below.
Systemd is now included in both the centos:7 and centos:latest base containers, but it is not active by default. In order to use systemd, you will need to include text similar to the example Dockerfile below:
## Dockerfile for systemd base image
@ -50,9 +50,7 @@ Currently, systemd in CentOS 7 has been removed and replaced with a `fakesystemd
FROM centos:7
MAINTAINER "you" <your@email.here>
ENV container docker
RUN yum -y swap -- remove fakesystemd -- install systemd systemd-libs
RUN yum -y update; yum clean all; \
(cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i ==
RUN (cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i ==
systemd-tmpfiles-setup.service ] || rm -f $i; done); \
rm -f /lib/systemd/system/multi-user.target.wants/*;\
rm -f /etc/systemd/system/*.wants/*;\
@ -65,7 +63,7 @@ VOLUME [ "/sys/fs/cgroup" ]
CMD ["/usr/sbin/init"]
```
This Dockerfile swaps out fakesystemd for the real package, but deletes a number of unit files which might cause issues. From here, you are ready to build your base image.
This Dockerfile deletes a number of unit files which might cause issues. From here, you are ready to build your base image.
```console
$ docker build --rm -t local/c7-systemd .
@ -90,13 +88,13 @@ $ docker build --rm -t local/c7-systemd-httpd
## Running a systemd enabled app container
In order to run a container with systemd, you will need to use the `--privileged` option mentioned earlier, as well as mounting the cgroups volumes from the host. Below is an example command that will run the systemd enabled httpd container created earlier.
In order to run a container with systemd, you will need to mount the cgroups volumes from the host. Below is an example command that will run the systemd enabled httpd container created earlier.
```console
$ docker run --privileged -ti -v /sys/fs/cgroup:/sys/fs/cgroup:ro -p 80:80 local/c7-systemd-httpd
$ docker run -ti -v /sys/fs/cgroup:/sys/fs/cgroup:ro -p 80:80 local/c7-systemd-httpd
```
This container is running with systemd in a limited context, but it must always be run as a privileged container with the cgroups filesystem mounted.
This container is running with systemd in a limited context, with the cgroups filesystem mounted. There have been reports that if you're using an Ubuntu host, you will need to add `-v /tmp/$(mktemp -d):/run` in addition to the cgroups mount.
# Supported Docker versions

14
centos/content.md
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@ -26,7 +26,7 @@ By default, the CentOS containers are built using yum's `nodocs` option, which h
# Systemd integration
Currently, systemd in CentOS 7 has been removed and replaced with a `fakesystemd` package for dependency resolution. This is due to systemd requiring the `CAP_SYS_ADMIN` capability, as well as being able to read the host's cgroups. If you wish to replace the fakesystemd package and use systemd normally, please follow the steps below.
Systemd is now included in both the centos:7 and centos:latest base containers, but it is not active by default. In order to use systemd, you will need to include text similar to the example Dockerfile below:
## Dockerfile for systemd base image
@ -34,9 +34,7 @@ Currently, systemd in CentOS 7 has been removed and replaced with a `fakesystemd
FROM centos:7
MAINTAINER "you" <your@email.here>
ENV container docker
RUN yum -y swap -- remove fakesystemd -- install systemd systemd-libs
RUN yum -y update; yum clean all; \
(cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i ==
RUN (cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i ==
systemd-tmpfiles-setup.service ] || rm -f $i; done); \
rm -f /lib/systemd/system/multi-user.target.wants/*;\
rm -f /etc/systemd/system/*.wants/*;\
@ -49,7 +47,7 @@ VOLUME [ "/sys/fs/cgroup" ]
CMD ["/usr/sbin/init"]
```
This Dockerfile swaps out fakesystemd for the real package, but deletes a number of unit files which might cause issues. From here, you are ready to build your base image.
This Dockerfile deletes a number of unit files which might cause issues. From here, you are ready to build your base image.
```console
$ docker build --rm -t local/c7-systemd .
@ -74,10 +72,10 @@ $ docker build --rm -t local/c7-systemd-httpd
## Running a systemd enabled app container
In order to run a container with systemd, you will need to use the `--privileged` option mentioned earlier, as well as mounting the cgroups volumes from the host. Below is an example command that will run the systemd enabled httpd container created earlier.
In order to run a container with systemd, you will need to mount the cgroups volumes from the host. Below is an example command that will run the systemd enabled httpd container created earlier.
```console
$ docker run --privileged -ti -v /sys/fs/cgroup:/sys/fs/cgroup:ro -p 80:80 local/c7-systemd-httpd
$ docker run -ti -v /sys/fs/cgroup:/sys/fs/cgroup:ro -p 80:80 local/c7-systemd-httpd
```
This container is running with systemd in a limited context, but it must always be run as a privileged container with the cgroups filesystem mounted.
This container is running with systemd in a limited context, with the cgroups filesystem mounted. There have been reports that if you're using an Ubuntu host, you will need to add `-v /tmp/$(mktemp -d):/run` in addition to the cgroups mount.