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Old 07-17-2011, 01:52 PM
Juliusz Chroboczek
 
Default A few observations about systemd

> (I'm the systemd maintainer in Debian)

(Shakes hands.)

> | Another case that I've actually been bitten by is that systemd
> | hard-wires runlevel 5 in its SV init compatibility code;

> It does?

I stand corrected, it's actually part of the configuration (symlink from
runlevel5.target to multi-user.target). Tollef, should the Debian
package change that?

> | Systemd is specific to Linux. This is strange, since the only feature
> | of Linux used by systemd that doesn't have an exact equivalent on other
> | systems, cgroups, is optional in systemd.

> TTBOMK, cgroups are not optional.

From cgroup.c, line 270:

if (path_is_mount_point("/sys/fs/cgroup/systemd") <= 0) {
log_warning("No control group support available, not creating root group.");
return 0;
}

Note that this returns 0, which stands for success.

-- Juliusz
 
Old 07-17-2011, 03:53 PM
Tollef Fog Heen
 
Default A few observations about systemd

]] Juliusz Chroboczek

Hi,

| I stand corrected, it's actually part of the configuration (symlink from
| runlevel5.target to multi-user.target). Tollef, should the Debian
| package change that?

: tfheen@qurzaw /lib/systemd/system > ls -l runlevel?.target
lrwxrwxrwx 1 root root 15 2011-07-07 13:37 runlevel0.target -> poweroff.target
lrwxrwxrwx 1 root root 13 2011-07-07 13:37 runlevel1.target -> rescue.target
lrwxrwxrwx 1 root root 17 2011-07-07 13:37 runlevel2.target -> multi-user.target
lrwxrwxrwx 1 root root 17 2011-07-07 13:37 runlevel3.target -> multi-user.target
lrwxrwxrwx 1 root root 17 2011-07-07 13:37 runlevel4.target -> multi-user.target
lrwxrwxrwx 1 root root 17 2011-07-07 13:37 runlevel5.target -> multi-user.target
lrwxrwxrwx 1 root root 13 2011-07-07 13:37 runlevel6.target -> reboot.target
: tfheen@qurzaw /lib/systemd/system >

This looks quite correct to me? (It's also what's shipped in the package.)

| > TTBOMK, cgroups are not optional.
|
| From cgroup.c, line 270:
|
| if (path_is_mount_point("/sys/fs/cgroup/systemd") <= 0) {
| log_warning("No control group support available, not creating root group.");
| return 0;
| }

hmm, ok. I suspect it will work much less well without cgroup support
even so, and in general upstream's not interested in supporting
non-linux even if you could make it limp along.

Cheers,
--
Tollef Fog Heen
UNIX is user friendly, it's just picky about who its friends are


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Old 07-17-2011, 04:02 PM
Juliusz Chroboczek
 
Default A few observations about systemd

> This looks quite correct to me? (It's also what's shipped in the package.)

I'm confused, then. After installing systemd the first time, systemd
happily ran the init.d scripts that I had disabled in rc2.d but left
enabled in rc{3,4,5}.d. We can probably agree that this is not the
expected behaviour on a Debian system.

Could you point me at where exactly systemd decides which of the rc?.d
services to start?

-- Juliusz
 
Old 07-17-2011, 04:07 PM
Matt Brown
 
Default A few observations about systemd

On Sun, Jul 17, 2011 at 4:53 PM, Tollef Fog Heen <tfheen@err.no> wrote:
>> | > TTBOMK, cgroups are not optional.
> |
> | From cgroup.c, line 270:
> |
> | * * if (path_is_mount_point("/sys/fs/cgroup/systemd") <= 0) {
> | * * * * * * log_warning("No control group support available, not creating root group.");
> | * * * * * * return 0;
> | * * }
>
> hmm, ok. *I suspect it will work much less well without cgroup support
> even so, and in general upstream's not interested in supporting
> non-linux even if you could make it limp along.

Indeed, more context is given in the bug mentioned just above that
stanza: https://bugzilla.redhat.com/show_bug.cgi?id=628004, in
particular Lennart's comment:
https://bugzilla.redhat.com/show_bug.cgi?id=628004#c27

"However, it will print a big big warning if you do this, and
will sleep for 5s so that people see it. And I will ignore all bugs reported
when things don't work properly if this is used"

The README also doesn't list cgroups as optional:

REQUIREMENTS:
Linux kernel >= 2.6.30 (with devtmpfs, cgroups; optional but
strongly recommended: autofs4, ipv6)

So cgroups is "optional", but not really if you want a supported
systemd installation

--
Matt Brown
matt@mattb.net.nz
Mob +353 86 608 7117 www.mattb.net.nz


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Old 07-17-2011, 04:26 PM
Juliusz Chroboczek
 
Default A few observations about systemd

> So cgroups is "optional", but not really if you want a supported
> systemd installation

Yes, and that's exactly what I find worrying about Lennart's attitude:
he presumes to impose his policy on you -- you must use Linux, you must
use a recent kernel with cgroups enabled, you're not supposed to use
shell scripts, etc.

I really like systemd, but not to the extent of giving up the ability to
pick my own policy.

-- Juliusz


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Old 07-17-2011, 04:51 PM
Juliusz Chroboczek
 
Default A few observations about systemd

Forwarded by permission from the author.

-- Juliusz
 
Old 07-17-2011, 07:31 PM
Tollef Fog Heen
 
Default A few observations about systemd

]] Juliusz Chroboczek

| > This looks quite correct to me? (It's also what's shipped in the package.)
|
| I'm confused, then. After installing systemd the first time, systemd
| happily ran the init.d scripts that I had disabled in rc2.d but left
| enabled in rc{3,4,5}.d. We can probably agree that this is not the
| expected behaviour on a Debian system.

This does sound somewhat surprising if nothing else pulled them in
through dependencies, yes.

What does systemctl show $service tell you? Particularly the
SysVRunLevels line is interesting to see that it picked up the lines
where it should be run properly.

| Could you point me at where exactly systemd decides which of the rc?.d
| services to start?

default.target
The default unit systemd starts at bootup. Usually this should be aliased (symlinked) to
multi-user.target or graphical.target.

The default unit systemd starts at bootup can be overridden with the systemd.unit= kernel command
line option.

Regards,
--
Tollef Fog Heen
UNIX is user friendly, it's just picky about who its friends are


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Old 07-17-2011, 07:37 PM
Adam Borowski
 
Default A few observations about systemd

On Sun, Jul 17, 2011 at 03:25:23PM +0200, Tollef Fog Heen wrote:
> | Systemd is bloated
> | ------------------
> |
> | Systemd is bloated. It apparently attempts to take over the roles of
> | init, cron, at, inet, ConsoleKit, sethostname, modprobe, mount -a, and
> | probably others. The result is that you end up running 50000 lines of
> | C code as PID 1, as compared to the 8000 lines of SV init or the 6000
> | lines of runit.
>
> as for trying to take over inetd's role: yes, it can replace inetd. You
> don't have to do that, though.

It does remove the important option to not have an inetd at all. And this
millenium, you'd have to look hard to find any use for inetd.

I guess a number of other parts of systemd share this problem.

--
1KB // Yo momma uses IPv4!


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Old 07-18-2011, 06:12 AM
Josselin Mouette
 
Default A few observations about systemd

Le dimanche 17 juillet 2011 * 13:54 +0200, Juliusz Chroboczek a écrit :
> Systemd is bloated
> Systemd is layered strangely
> Systemd hard-wires special cases
> Systemd deprecates shell scripts

I disagree these are real, practical issues - some of these aren’t even
problems but features.

> Systemd is Linux-specific
> Systemd's author is annoying

Developing for Linux-only is fine, but Lennart has explicitly said that
he wouldn’t remotely consider accepting portability patches, which goes
further than any other piece of free software I had to deal with.

We need one and only one init system in Debian. (Those considering
maintaining several init systems in parallel do not see how stupid,
bloated and error-prone it would be to require all daemon maintainers to
maintain more init scripts than they do now.) I’d like to see systemd as
that one init system, but this challenges the future of kfreebsd.

If kfreebsd is really more than a toy operating system and we want users
to do something with it, the porters need to maintain a kfreebsd branch
of a modern init system (be it upstart or systemd).

--
.'`. Josselin Mouette
: :' :
`. `'
`-
 
Old 07-18-2011, 09:30 AM
Jon Dowland
 
Default A few observations about systemd

On Sun, Jul 17, 2011 at 06:26:34PM +0200, Juliusz Chroboczek wrote:
> Yes, and that's exactly what I find worrying about Lennart's attitude:
> he presumes to impose his policy on you -- you must use Linux, you must
> use a recent kernel with cgroups enabled, you're not supposed to use
> shell scripts, etc.

Whilst I share your concerns about Poettering's attitude (and my heart sank
only three lines into his reply that you forwarded to -devel), I think only
supporting Linux is entirely his perogative: It's his project, his time and he
can support what he wants. (Or it's Red Hat's time, and they can support
whatever they want). Likewise, a recent kernel does not seem like a problem,
and cgroups seems like a fairly core part of what systemd does.

The shell script thing I have more of a problem with, although I take his point
about the quality of init scripts at present[1].

I don't suppose it would be worth maintaining a patch-set in Debian to support
other OSs: In a hypothetical future where systemd was the default init system
for Debian, it's probably less work to support multiple init systems and let
K*BSD/Hurd/*[2] pick another.


[1] whilst implementing puppet, I filed #629654 and #629910, and I was just
getting started ☹
[2] has anyone started a Debian/Plan 9 yet?


--
Jon Dowland


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