40n8.me/baseimage-docker
1
0
Fork 0
mirror of /repos/baseimage-docker.git synced 2025-12-30 08:01:31 +01:00
Code Issues Releases Wiki Activity

Revert "Document another reason why SSH access is important"

Browse Source 
This reverts commit c51ba582e9c499ed5fc82ff0aabc20c79caece60.
This commit is contained in:
Hongli Lai (Phusion) 2013-11-13 12:13:06 +01:00
parent c51ba582e9
commit c7eb6e98e2
1 changed files with 1 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
README.md
View File

@ -13,8 +13,6 @@ Baseimage-docker is available for pulling from on [the Docker registry](https://
Ubuntu is not designed to be run inside docker. Its init system, Upstart, assumes that it's running on either real hardware or virtualized hardware, but not inside a Docker container. But inside a container you don't want a full system anyway, you want a minimal system. But configuring that minimal system for use within a container has many strange corner cases that are hard to get right if you are not intimately familiar with the Unix system model. This can cause a lot of strange problems. Ubuntu is not designed to be run inside docker. Its init system, Upstart, assumes that it's running on either real hardware or virtualized hardware, but not inside a Docker container. But inside a container you don't want a full system anyway, you want a minimal system. But configuring that minimal system for use within a container has many strange corner cases that are hard to get right if you are not intimately familiar with the Unix system model. This can cause a lot of strange problems.
There are also other problems, like `apt-get install` failing when Upstart is not running (which is the case when running `docker build`), or the fact that not having SSH access into your container makes it impossible to safely store persistent data in the container.
Baseimage-docker gets everything right. The "Contents" section describes all the things that it modifies. Baseimage-docker gets everything right. The "Contents" section describes all the things that it modifies.
### Why use baseimage-docker? ### Why use baseimage-docker?
@ -36,7 +34,7 @@ You can configure the stock `ubuntu` image yourself from your Dockerfile, so why
| A **correct** init process | According to the Unix process model, [the init process](https://en.wikipedia.org/wiki/Init) -- PID 1 -- inherits all [orphaned child processes](https://en.wikipedia.org/wiki/Orphan_process) and must [reap them](https://en.wikipedia.org/wiki/Wait_(system_call). Most Docker containers do not have an init process that does this correctly, and as a result their containers become filled with [zombie processes](https://en.wikipedia.org/wiki/Zombie_process) over time. <br><br>Furthermore, `docker stop` sends SIGTERM to the init process, which is then supposed to stop all services. Unfortunately most init systems don't do this correctly within Docker since they're built for hardware shutdowns instead. This causes processes to be hard killed with SIGKILL, which doesn't give them a chance to correctly deinitialize things. This can cause file corruption. <br><br>Baseimage-docker comes with an init process `/sbin/my_init` that performs both of these tasks correctly. | | A **correct** init process | According to the Unix process model, [the init process](https://en.wikipedia.org/wiki/Init) -- PID 1 -- inherits all [orphaned child processes](https://en.wikipedia.org/wiki/Orphan_process) and must [reap them](https://en.wikipedia.org/wiki/Wait_(system_call). Most Docker containers do not have an init process that does this correctly, and as a result their containers become filled with [zombie processes](https://en.wikipedia.org/wiki/Zombie_process) over time. <br><br>Furthermore, `docker stop` sends SIGTERM to the init process, which is then supposed to stop all services. Unfortunately most init systems don't do this correctly within Docker since they're built for hardware shutdowns instead. This causes processes to be hard killed with SIGKILL, which doesn't give them a chance to correctly deinitialize things. This can cause file corruption. <br><br>Baseimage-docker comes with an init process `/sbin/my_init` that performs both of these tasks correctly. |
| Fixes APT incompatibilities with Docker | See https://github.com/dotcloud/docker/issues/1024. | | Fixes APT incompatibilities with Docker | See https://github.com/dotcloud/docker/issues/1024. |
| syslog-ng | A syslog daemon is necessary so that many services - including the kernel itself - can correctly log to /var/log/syslog. If no syslog daemon is running, a lot of important messages are silently swallowed. <br><br>Only listens locally. | | syslog-ng | A syslog daemon is necessary so that many services - including the kernel itself - can correctly log to /var/log/syslog. If no syslog daemon is running, a lot of important messages are silently swallowed. <br><br>Only listens locally. |
| ssh server | Allows you to easily login to your container to inspect or administer things. If your container has persistent data (e.g. runs a database) then you **must** have SSH access, otherwise there is no way to dump or backup your data! This is because bind mounts in Docker cannot be changed after a container is launched. <br><br>Password and challenge-response authentication are disabled by default. Only key authentication is allowed.<br>It allows an predefined key by default to make debugging easy. You should replace this ASAP. See instructions. | | ssh server | Allows you to easily login to your container to inspect or administer things. <br><br>Password and challenge-response authentication are disabled by default. Only key authentication is allowed.<br>It allows an predefined key by default to make debugging easy. You should replace this ASAP. See instructions. |
| cron | The cron daemon must be running for cron jobs to work. | | cron | The cron daemon must be running for cron jobs to work. |
| [runit](http://smarden.org/runit/) | Replaces Ubuntu's Upstart. Used for service supervision and management. Much easier to use than SysV init and supports restarting daemons when they crash. Much easier to use and more lightweight than Upstart. | | [runit](http://smarden.org/runit/) | Replaces Ubuntu's Upstart. Used for service supervision and management. Much easier to use than SysV init and supports restarting daemons when they crash. Much easier to use and more lightweight than Upstart. |
| `setuser` | A tool for running a command as another user. Easier to use than `su`, has a smaller attack vector than `sudo`, and unlike `chpst` this tool sets `$HOME` correctly. Available as `/sbin/setuser`. | | `setuser` | A tool for running a command as another user. Easier to use than `su`, has a smaller attack vector than `sudo`, and unlike `chpst` this tool sets `$HOME` correctly. Available as `/sbin/setuser`. |