Jess Frazelle 736052e309 remove need for any caps

Signed-off-by: Jess Frazelle <jess@mesosphere.com>

2016-04-17 21:37:13 -07:00

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binctr

Create fully static, including rootfs embedded, binaries that pop you directly into a container. Can be run by an unprivileged user.

This is based off a crazy idea from @crosbymichael who first embedded an image in a binary :D

NOTE

You may have noticed you can't file an issue. That's because this is using a crazy person's (aka my) fork of libcontainer and until I get the patches into upstream there's no way in hell I'm fielding issues from whoever is crazy enough to try this.

If you are interested, I have started a thread on the mailing list with my proposed steps to make this a reality. Note, adding a +1 is not of any value to anyone though.

Nginx running with my user "jessie".

Building

This uses the new Golang vendoring so you need go 1.6 or GO15VENDOREXPERIMENT=1 in your env.

You will also need libapparmor-dev and libseccomp-dev.

Most importantly you need userns in your kernel (CONFIG_USER_NS=y) or else this won't even work.

$ make static
Static container created at: ./bin/alpine
Run with ./bin/alpine

# building a different base image
$ make static IMAGE=busybox
Static container created at: ./bin/busybox
Run with ./bin/busybox

Running

$ ./alpine
$ ./busybox --read-only

Running with custom commands & args

# let's make an nginx binary
$ make static IMAGE=nginx
Static container created at: ./bin/nginx
Run with ./bin/nginx

$ ./bin/nginx nginx -g "daemon off;"

# But we have no networking! Don't worry we can fix this
# Let's install my super cool binary for setting up networking in a container
$ go get github.com/jfrazelle/netns

# now we can add this as a prestart hook
$ ./bin/nginx --hook prestart:netns nginx -g "daemon off;"

# let's get the ip file
$ cat .ip
172.19.0.10

Success!

Usage

$ ./bin/alpine -h
 _     _            _
| |__ (_)_ __   ___| |_ _ __
| '_ \| | '_ \ / __| __| '__|
| |_) | | | | | (__| |_| |
|_.__/|_|_| |_|\___|\__|_|

 Fully static, self-contained container including the rootfs
 that can be run by an unprivileged user.

 Embedded Image: alpine - sha256:70c557e50ed630deed07cbb0dc4d28aa0f2a485cf7af124cc48f06bce83f784b
 Version: 0.1.0
 GitCommit: 13fcd27-dirty

  -D	run in debug mode
  -console string
    	the pty slave path for use with the container
  -d	detach from the container's process
  -hook value
    	Hooks to prefill into spec file. (ex. --hook prestart:netns) (default [])
  -id string
    	container ID (default "nginx")
  -pid-file string
    	specify the file to write the process id to
  -read-only
    	make container filesystem readonly
  -root string
    	root directory of container state, should be tmpfs (default "/run/binctr")
  -t	allocate a tty for the container (default true)
  -v	print version and exit (shorthand)
  -version
    	print version and exit

Cool things

The binary spawned does NOT need to oversee the container process if you run in detached mode with a PID file. You can have it watched by the user mode systemd so that this binary is really just the launcher :)

Caveats

cgroups: coming soon

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