rkt: add --hostname option #2251

iaguis · 2016-03-04T15:06:10Z

It allows the user to specify a host name for the pod. If not specified, it will be "rkt-$PODUUID".

This approach might not be OK if we want to use systemd-resolved, apparently it expects container's machine name to match the hostname.

cc @steveej @yifan-gu @sjpotter

Fixes #2245

sjpotter · 2016-03-04T17:07:18Z

@iaguis so would resolved break if a user changed the hostname within the container themselves? and is that a bad thing?

iaguis · 2016-03-04T17:13:31Z

I don't think I have enough context to answer that. Maybe @steveej can shed some light on it.

yifan-gu · 2016-03-04T20:26:45Z

stage1/init/init.go

+	// According to systemd manual (https://www.freedesktop.org/software/systemd/man/hostname.html) :
+	// "The /etc/hostname file configures the name of the local system that is set
+	// during boot using the sethostname system call"
+	if hostname == "" {


This is not the common place. As the case "kvm" returns directly above.

Updated, I don't know why this comment is still showing up on github...

Code was not changed, only moved, maybe this is a reason?

steveej · 2016-03-08T12:11:12Z

@sjpotter

@iaguis so would resolved break if a user changed the hostname within the container themselves? and is that a bad thing?

This is not something we can easily answer in general, and therefore nothing we have to worry about immediately. You can read https://www.freedesktop.org/software/systemd/man/nss-mymachines.html# to get an idea what can influence the configuration. I just checked the /etc/nsswitch.conf inside CoreOS, which is also used within the default stage1, and neither mymachine nor myhostname is configured.

iaguis · 2016-03-08T12:35:01Z

FWIW with mymachines in /etc/nsswitch.conf, resolution works fine with rkt and a different --hostname.

jellonek · 2016-03-08T13:17:01Z

g2k
LGTM

iaguis · 2016-03-08T14:19:37Z

If the resolved thing is not something we should worry about for now, I'm OK with merging this.

What do you think, @steveej?

jellonek · 2016-03-08T14:24:45Z

Is it possible that someone will add additional functional test for this before merge? It's not something what i need there strongly, but... (i know that i should ask about this @mstachowski when this was added to kvm flavor, but still...)

iaguis · 2016-03-08T14:26:47Z

I can add one if we decide it's ok to merge :)

iaguis · 2016-03-08T15:11:07Z

Added a functional test

steveej · 2016-03-08T16:13:38Z

It will break fly :-(

steveej · 2016-03-08T16:16:19Z

How about we introduce annotations for stage1 ACIs where supported commands (run, exec, gc) and their supported flags (--hostname, --dns, --port, ...) can be declared? stage0 could then check if it can pass all requested flags to the stage1 and either skip them or error out cleanly. Behavior on incompatibility should default to error but also be settable via a stage0 flag.

jellonek · 2016-03-10T14:41:59Z

Seems to me a bit too complicated, but reasonable. I have no strong feelings about this...

But... This will open a door for new features (and so incompatibility between flavors) supported by one flavor or group of them - this seems more scary and exciting ;)

iaguis · 2016-03-14T12:07:36Z

How about we introduce annotations for stage1 ACIs where supported commands (run, exec, gc) and their supported flags (--hostname, --dns, --port, ...) can be declared? stage0 could then check if it can pass all requested flags to the stage1 and either skip them or error out cleanly. Behavior on incompatibility should default to error but also be settable via a stage0 flag.

This is a pretty big change, can we just ignore the flag in fly for now (like we do with the rest) so we can get this and discuss that in a new issue?

alban · 2016-03-14T14:45:30Z

Documentation/subcommands/run-prepared.md

 | `--dns` |  `` | IP Address | Name server to write in `/etc/resolv.conf`. It can be specified several times |
 | `--dns-opt` |  `` | Option as described in the options section in resolv.conf(5) | DNS option to write in `/etc/resolv.conf`. It can be specified several times |
 | `--dns-search` |  `` | Domain name | DNS search domain to write in `/etc/resolv.conf`. It can be specified several times |
+| `--hostname` |  `` | A host name | Pod's hostname. If empty, it will be the "rkt-$PODUUID" |


iaguis · 2016-03-14T14:58:39Z

This is a pretty big change, can we just ignore the flag in fly for now (like we do with the rest) so we can get this and discuss that in a new issue?

I added a commit doing that, addressed the review and added --hostname to the stage1 implementors guide.

alban · 2016-03-14T15:01:23Z

The --hostname is not in the documentation:
https://github.com/coreos/rkt/blob/master/Documentation/devel/stage1-implementors-guide.md#arguments

I am not sure about adding a new parameter without introducing versioning in annotations as explained here:
#2173 (comment)

steveej · 2016-03-15T17:36:44Z

How about we introduce annotations for stage1 ACIs where supported commands (run, exec, gc) and their supported flags (--hostname, --dns, --port, ...) can be declared? stage0 could then check if it can pass all requested flags to the stage1 and either skip them or error out cleanly. Behavior on incompatibility should default to error but also be settable via a stage0 flag.

This is a pretty big change, can we just ignore the flag in fly for now (like we do with the rest) so we can get this and discuss that in a new issue?

Could you break it apart to identify the most difficult/time-consuming steps that may be postponed?

jonboulle · 2016-03-16T11:25:37Z

This is a pretty big change, can we just ignore the flag in fly for now (like we do with the rest) so we can get this and discuss that in a new issue?

Let's do this. There are many outstanding issues with the fly/stage1 thing that need to be addressed, but adding another ignored flag is only making the situation marginally worse.

yifan-gu · 2016-03-16T20:17:59Z

I think this also affects how we get logs from journactl. journalctl -m _HOSTNAME=rkt-uuid doesn't seem to work now in this example: https://github.com/coreos/rkt/blob/master/Documentation/using-rkt-with-systemd.md#systemd-run

iaguis · 2016-03-17T16:01:36Z

You can do journalctl -m _MACHINE_ID=${UUID_WITHOUT_DASHES}.

krnowak · 2016-03-17T16:11:21Z

Documentation/devel/stage1-implementors-guide.md

 * `--net[=$NET1,$NET2,...]` to configure the creation of a contained network.
  See the [rkt networking documentation](../networking.md) for details.
 * `--mds-token=$TOKEN` passes the auth token to the apps via `AC_METADATA_URL` env var
+* `--hostname=$HOSTNAME` configures the host name of the pod. If empty, it will be "rkt-$PODUUID". Only available from ABI version 2.


Probably would be easier to read if there was a separate section like "flags added in interface version 2".

sjpotter · 2016-03-17T16:17:13Z

yea, we figured that out, but strangely, it doesn't work on my ubuntu box.
( _HOSTNAME or _MACHINE_ID)

iaguis · 2016-03-17T16:37:04Z

Updated.

alban · 2016-03-17T16:39:30Z

stage0/run.go

+	}
+
+	if cfg.Hostname != "" {
+		if s1v > 1 {


I wonder about defining a constant in interface.go, and then:

if s1v > interfaceVersionHostname {

Dunno, it might be troublesome later. interfaceVersionThisThatAndOneMoreThingIfIRemeberedEverything.

That's how German works, right?

actually, instead of a constant, define a function in interface.go:

if interfaceVersionSupportsHostname(s1v) { }

Or maybe make s1v an object instead of an integer, so you could add functions to it like func (s1v Stage1InterfaceVersion) SupportsHostname() bool {}

That would be an idea for a separate PR. ;P

I'll think about it... :P

krnowak · 2016-03-17T16:51:52Z

LFAD, but maybe you'll want another stamp.

It allows the user to specify a host name for the pod. If not specified, it will be "rkt-$PODUUID".

alban · 2016-03-17T17:04:53Z

LGTM if green

rkt: add --hostname option

iaguis added kind/enhancement component/stage1 component/stage0 priority/P1 do not merge labels Mar 4, 2016

iaguis force-pushed the iaguis/hostname branch from ef933fb to 5a6cd63 Compare March 4, 2016 15:35

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iaguis force-pushed the iaguis/hostname branch from 5a6cd63 to 13c1560 Compare March 7, 2016 14:46

iaguis removed the do not merge label Mar 8, 2016

iaguis changed the title ~~(WIP) rkt: add --hostname option~~ rkt: add --hostname option Mar 8, 2016

borqosky mentioned this pull request Mar 9, 2016

/etc/hosts is not needed during run-prepared command through kubelet with rkt kubernetes/kubernetes#22739

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iaguis added this to the v1.2.0 milestone Mar 14, 2016

alban reviewed Mar 14, 2016
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iaguis force-pushed the iaguis/hostname branch from 8af7405 to f81321a Compare March 14, 2016 14:51

jonboulle mentioned this pull request Mar 16, 2016

stage1/gc: remove journal link #2289

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iaguis force-pushed the iaguis/hostname branch from b8639b0 to 592124d Compare March 17, 2016 15:58

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alban reviewed Mar 17, 2016
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iaguis added 4 commits March 17, 2016 18:00

rkt: add --hostname option

5687d8c

It allows the user to specify a host name for the pod. If not specified, it will be "rkt-$PODUUID".

Documentation: document --hostname

0b27d04

functional tests: add a --hostname test

1d68792

Documentation: add --hostname to the stage1 implementors guide

c2300ea

iaguis force-pushed the iaguis/hostname branch from 544e009 to c2300ea Compare March 17, 2016 17:01

iaguis added a commit that referenced this pull request Mar 17, 2016

Merge pull request #2251 from kinvolk/iaguis/hostname

ff0813b

rkt: add --hostname option

iaguis merged commit ff0813b into rkt:master Mar 17, 2016

achanda mentioned this pull request Mar 23, 2016

Allow setting hostname for rkt driver hashicorp/nomad#967

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jonboulle mentioned this pull request Jul 1, 2016

stage1/fly: respect runtimeApp App's MountPoints #2852

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rkt: add --hostname option #2251

rkt: add --hostname option #2251

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