On Mon, 2013-11-25 at 21:43 -0500, Stéphane Graber wrote:
> Haha,
>
> I was wondering how long it'd take before we got the first comment about
> systemd's own cgroup manager :)
>
> To try and keep this short, there are a lot of cases where systemd's
> plan of having an in-pid1 manager, as practical as it's for them, just
> isn't going to work for us.
>
> I believe our design makes things a bit cleaner by not having it tied to
> any specific init system or feature and have a relatively low level,
> very simple API that people can use as a building block for anything
> that wants to manage cgroups.
>
> At this point in time, there's no hard limitation for having one or more
> processes writing to the cgroup hierarchy, as much as some people may
> want this to change. I very much doubt it'll happen any time soon and
> until then, even if not perfectly adequate, there won't be any problem
> running both systemd's manager and our own.
>
> There's also the possibility if someone felt sufficiently strongly about
> this to contribute patches, to have our manager talk to systemd's if
> present and go through their manager instead of accessing cgroupfs
> itself. That's assuming systemd offers a sufficiently low level API that
> could be used for that without bringing an unreasonable amount of
> dependencies to our code.
>
>
> I don't want this thread to turn into some kind of flamewar or similarly
> overheated discussion about systemd vs everyone else, so I'll just state
> that from my point of view (and I suspect that of the group who worked
> on this early draft), systemd's manager while perfect for grouping and
> resource allocation for systemd units and user sessions doesn't quite
> fit our bill with regard to supporting multiple level of full
> distro-agnostic containers using nesting and mixing user namespaces.
> It also has what as a non-systemd person I consider a big drawback of
> being built into an init system which quite a few major distributions
> don't use (specifically those distros that account for the majority of
> LXC's users).
>
> I think there's room for two implementations and competition (even if we
> have slightly different goals) is a good thing and will undoubtedly help
> both project consider use cases they didn't think of leading to a better
> solution for everyone. And if some day one of the two wins or we can
> somehow converge into a solution that works for everyone, that'd be
> great. But our discussions at Linux Plumbers and other conferences have
> shown that this isn't going to happen now, so it's best to stop arguing
> and instead get some stuff done.
Concur. And, as you know, I'm not a fan or supporter of that camp. I
just want to make sure everyone is aware of all the gorillas in the room
before the fecal flakes hit the rapidly whirling blades.
That being said, I think this is a laudable goal. If we do it right, it
well can become the standard they have to adhere to.
Regards,
Mike
> On Mon, Nov 25, 2013 at 09:18:04PM -0500, Michael H. Warfield wrote:
> > Serge...
> >
> > You have no idea how much I dread mentioning this (well, after
> > LinuxPlumbers, maybe you can) but... You do realize that some of this
> > is EXACTLY what the systemd crowd was talking about there in NOLA back
> > then. I sat in those session grinding my teeth and listening to
> > comments from some others around me about when systemd might subsume
> > bash or even vi or quake.
> >
> > Somehow, you and others have tagged me as a "systemd expert" but I am
> > far from it and even you noted that Lennart and I were on the edge of a
> > physical discussion when I made some "off the cuff" remarks there about
> > systemd design during my talk. I personally rank systemd in the same
> > category as NetworkMangler (err, NetworkManager) in its propensity for
> > committing inexplicable random acts of terrorism and changing its
> > behavior from release to release to release. I'm not a fan and I'm not
> > an expert, but I have to be involved with it and watch the damned thing
> > like a trapped rat, like it or not.
> >
> > Like it or not, we can not go off on divergent designs. As much as they
> > have delusions of taking over the Linux world, they are still going to
> > be a major factor and this sort of thing needs to be coordinated. We
> > are going to need exactly what you are proposing whether we have systemd
> > in play or not. IF we CAN kick it to the curb, when we need to, we
> > still need to know how to without tearing shit up and breaking shit that
> > thinks it's there. Ideally, it shouldn't matter if systemd where in
> > play or not.
> >
> > All I ask is that we not get too far off track that we have a major
> > architectural divergence here. The risk is there.
> >
> > Mike
> >
> >
> > On Mon, 2013-11-25 at 22:43 +0000, Serge E. Hallyn wrote:
> > > Hi,
> > >
> > > as i've mentioned several times, I want to write a standalone cgroup
> > > management daemon. Basic requirements are that it be a standalone
> > > program; that a single instance running on the host be usable from
> > > containers nested at any depth; that it not allow escaping ones
> > > assigned limits; that it not allow subjegating tasks which do not
> > > belong to you; and that, within your limits, you be able to parcel
> > > those limits to your tasks as you like.
> > >
> > > Additionally, Tejun has specified that we do not want users to be
> > > too closely tied to the cgroupfs implementation. Therefore
> > > commands will be just a hair more general than specifying cgroupfs
> > > filenames and values. I may go so far as to avoid specifying
> > > specific controllers, as AFAIK there should be no redundancy in
> > > features. On the other hand, I don't want to get too general.
> > > So I'm basing the API loosely on the lmctfy command line API.
> > >
> > > One of the driving goals is to enable nested lxc as simply and safely as
> > > possible. If this project is a success, then a large chunk of code can
> > > be removed from lxc. I'm considering this project a part of the larger
> > > lxc project, but given how central it is to systems management that
> > > doesn't mean that I'll consider anyone else's needs as less important
> > > than our own.
> > >
> > > This document consists of two parts. The first describes how I
> > > intend the daemon (cgmanager) to be structured and how it will
> > > enforce the safety requirements. The second describes the commands
> > > which clients will be able to send to the manager. The list of
> > > controller keys which can be set is very incomplete at this point,
> > > serving mainly to show the approach I was thinking of taking.
> > >
> > > Summary
> > >
> > > Each 'host' (identified by a separate instance of the linux kernel) will
> > > have exactly one running daemon to manage control groups. This daemon
> > > will answer cgroup management requests over a dbus socket, located at
> > > /sys/fs/cgroup/manager. This socket can be bind-mounted into various
> > > containers, so that one daemon can support the whole system.
> > >
> > > Programs will be able to make cgroup requests using dbus calls, or
> > > indirectly by linking against lmctfy which will be modified to use the
> > > dbus calls if available.
> > >
> > > Outline:
> > > . A single manager, cgmanager, is started on the host, very early
> > > during boot. It has very few dependencies, and requires only
> > > /proc, /run, and /sys to be mounted, with /etc ro. It will mount
> > > the cgroup hierarchies in a private namespace and set defaults
> > > (clone_children, use_hierarchy, sane_behavior, release_agent?) It
> > > will open a socket at /sys/fs/cgroup/cgmanager (in a small tmpfs).
> > > . A client (requestor 'r') can make cgroup requests over
> > > /sys/fs/cgroup/manager using dbus calls. Detailed privilege
> > > requirements for r are listed below.
> > > . The client request will pertain an existing or new cgroup A. r's
> > > privilege over the cgroup must be checked. r is said to have
> > > privilege over A if A is owned by r's uid, or if A's owner is mapped
> > > into r's user namespace, and r is root in that user namespace.
> > > . The client request may pertain a victim task v, which may be moved
> > > to a new cgroup. In that case r's privilege over both the cgroup
> > > and v must be checked. r is said to have privilege over v if v
> > > is mapped in r's pid namespace, v's uid is mapped into r's user ns,
> > > and r is root in its userns. Or if r and v have the same uid
> > > and v is mapped in r's pid namespace.
> > > . r's credentials will be taken from socket's peercred, ensuring that
> > > pid and uid are translated.
> > > . r passes PID(v) as a SCM_CREDENTIAL, so that cgmanager receives the
> > > translated global pid. It will then read UID(v) from /proc/PID(v)/status,
> > > which is the global uid, and check /proc/PID(r)/uid_map to see whether
> > > UID is mapped there.
> > > . dbus-send can be enhanced to send a pid as SCM_CREDENTIAL to have
> > > the kernel translate it for the reader. Only 'move task v to cgroup
> > > A' will require a SCM_CREDENTIAL to be sent.
> > >
> > > Privilege requirements by action:
> > > * Requestor of an action (r) over a socket may only make
> > > changes to cgroups over which it has privilege.
> > > * Requestors may be limited to a certain #/depth of cgroups
> > > (to limit memory usage) - DEFER?
> > > * Cgroup hierarchy is responsible for resource limits
> > > * A requestor must either be uid 0 in its userns with victim mapped
> > > ito its userns, or the same uid and in same/ancestor pidns as the
> > > victim
> > > * If r requests creation of cgroup '/x', /x will be interpreted
> > > as relative to r's cgroup. r cannot make changes to cgroups not
> > > under its own current cgroup.
> > > * If r is not in the initial user_ns, then it may not change settings
> > > in its own cgroup, only descendants. (Not strictly necessary -
> > > we could require the use of extra cgroups when wanted, as lxc does
> > > currently)
> > > * If r requests creation of cgroup '/x', it must have write access
> > > to its own cgroup (not strictly necessary)
> > > * If r requests chown of cgroup /x to uid Y, Y is passed in a
> > > ucred over the unix socket, and therefore translated to init
> > > userns.
> > > * if r requests setting a limit under /x, then
> > > . either r must be root in its own userns, and UID(/x) be mapped
> > > into its userns, or else UID(r) == UID(/x)
> > > . /x must not be / (not strictly necessary, all users know to
> > > ensure an extra cgroup layer above '/')
> > > . setns(UIDNS(r)) would not work, due to in-kernel capable() checks
> > > which won't be satisfied. Therefore we'll need to do privilege
> > > checks ourselves, then perform the write as the host root user.
> > > (see devices.allow/deny). Further we need to support older kernels
> > > which don't support setns for pid.
> > > * If r requests action on victim V, it passes V's pid in a ucred,
> > > so that gets translated.
> > > Daemon will verify that V's uid is mapped into r's userns. Since
> > > r is either root or the same uid as V, it is allowed to classify.
> > >
> > > The above addresses
> > > * creating cgroups
> > > * chowning cgroups
> > > * setting cgroup limits
> > > * moving tasks into cgroups
> > > . but does not address a 'cgexec <group> -- command' type of behavior.
> > > * To handle that (specifically for upstart), recommend that r do:
> > > if (!pid) {
> > > request_reclassify(cgroup, getpid());
> > > do_execve();
> > > }
> > > . alternatively, the daemon could, if kernel is new enough, setns to
> > > the requestor's namespaces to execute a command in a new cgroup.
> > > The new command would be daemonized to that pid namespaces' pid 1.
> > >
> > > Types of requests:
> > > * r requests creating cgroup A'/A
> > > . lmctfy/cli/commands/create.cc
> > > . Verify that UID(r) mapped to 0 in r's userns
> > > . R=cgroup_of(r)
> > > . Verify that UID(R) is mapped into r's userns
> > > . Create R/A'/A
> > > . chown R/A'/A to UID(r)
> > > * r requests to move task x to cgroup A.
> > > . lmctfy/cli/commands/enter.cc
> > > . r must send PID(x) as ancillary message
> > > . Verify that UID(r) mapped to 0 in r's userns, and UID(x) is mapped into
> > > that userns
> > > (is it safe to allow if UID(x) == UID(r))?
> > > . R=cgroup_of(r)
> > > . Verify that R/A is owned by UID(r) or UID(x)? (not sure that's needed)
> > > . echo PID(x) >> /R/A/tasks
> > > * r requests chown of cgroup A to uid X
> > > . X is passed in ancillary message
> > > * ensures it is valid in r's userns
> > > * maps the userid to host for us
> > > . Verify that UID(r) mapped to 0 in r's userns
> > > . R=cgroup_of(r)
> > > . Chown R/A to X
> > > * r requests cgroup A's 'property=value'
> > > . Verify that either
> > > * A != ''
> > > * UID(r) == 0 on host
> > > In other words, r in a userns may not set root cgroup settings.
> > > . Verify that UID(r) mapped to 0 in r's userns
> > > . R=cgroup_of(r)
> > > . Set property=value for R/A
> > > * Expect kernel to guarantee hierarchical constraints
> > > * r requests deletion of cgroup A
> > > . lmctfy/cli/commands/destroy.cc (without -f)
> > > . same requirements as setting 'property=value'
> > > * r requests purge of cgroup A
> > > . lmctfy/cli/commands/destroy.cc (with -f)
> > > . same requirements as setting 'property=value'
> > >
> > > Long-term we will want the cgroup manager to become more intelligent -
> > > to place its own limits on clients, to address cpu and device hotplug,
> > > etc. Since we will not be doing that in the first prototype, the daemon
> > > will not keep any state about the clients.
> > >
> > > Client DBus Message API
> > >
> > > <name>: a-zA-Z0-9
> > > <name>: "a-zA-Z0-9 "
> > > <controllerlist>: <controller1>[:controllerlist]
> > > <valueentry>: key:value
> > > <valueentry>: frozen
> > > <valueentry>: thawed
> > > <values>: valueentry[:values]
> > > keys:
> > > {memory,swap}.{limit,soft_limit}
> > > cpus_allowed # set of allowed cpus
> > > cpus_fraction # % of allowed cpus
> > > cpus_number # number of allowed cpus
> > > cpu_share_percent # percent of cpushare
> > > devices_whitelist
> > > devices_blacklist
> > > net_prio_index
> > > net_prio_interface_map
> > > net_classid
> > > hugetlb_limit
> > > blkio_weight
> > > blkio_weight_device
> > > blkio_throttle_{read,write}
> > > readkeys:
> > > devices_list
> > > {memory,swap}.{failcnt,max_use,limitnuma_stat}
> > > hugetlb_max_usage
> > > hugetlb_usage
> > > hugetlb_failcnt
> > > cpuacct_stat
> > > <etc>
> > > Commands:
> > > ListControllers
> > > Create <name> <controllerlist> <values>
> > > Setvalue <name> <values>
> > > Getvalue <name> <readkeys>
> > > ListChildren <name>
> > > ListTasks <name>
> > > ListControllers <name>
> > > Chown <name> <uid>
> > > Chown <name> <uid>:<gid>
> > > Move <pid> <name> [[ pid is sent as a SCM_CREDENTIAL ]]
> > > Delete <name>
> > > Delete-force <name>
> > > Kill <name>
> > >
> > > ------------------------------------------------------------------------------
> > > Shape the Mobile Experience: Free Subscription
> > > Software experts and developers: Be at the forefront of tech innovation.
> > > Intel(R) Software Adrenaline delivers strategic insight and game-changing
> > > conversations that shape the rapidly evolving mobile landscape. Sign up now.
> > > http://pubads.g.doubleclick.net/gampad/clk?id=63431311&iu=/4140/ostg.clktrk
> > > _______________________________________________
> > > Lxc-devel mailing list
> > > Lxc-devel@xxxxxxxxxxxxxxxxxxxxx
> > > https://lists.sourceforge.net/lists/listinfo/lxc-devel
> > >
> >
> > --
> > Michael H. Warfield (AI4NB) | (770) 978-7061 | mhw@xxxxxxxxxxxx
> > /\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/
> > NIC whois: MHW9 | An optimist believes we live in the best of all
> > PGP Key: 0x674627FF | possible worlds. A pessimist is sure of it!
> >
>
>
>
> > ------------------------------------------------------------------------------
> > Shape the Mobile Experience: Free Subscription
> > Software experts and developers: Be at the forefront of tech innovation.
> > Intel(R) Software Adrenaline delivers strategic insight and game-changing
> > conversations that shape the rapidly evolving mobile landscape. Sign up now.
> > http://pubads.g.doubleclick.net/gampad/clk?id=63431311&iu=/4140/ostg.clktrk
>
> > _______________________________________________
> > Lxc-devel mailing list
> > Lxc-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.sourceforge.net/lists/listinfo/lxc-devel
>
>
> ------------------------------------------------------------------------------
> Shape the Mobile Experience: Free Subscription
> Software experts and developers: Be at the forefront of tech innovation.
> Intel(R) Software Adrenaline delivers strategic insight and game-changing
> conversations that shape the rapidly evolving mobile landscape. Sign up now.
> http://pubads.g.doubleclick.net/gampad/clk?id=63431311&iu=/4140/ostg.clktrk
> _______________________________________________
> Lxc-devel mailing list
> Lxc-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.sourceforge.net/lists/listinfo/lxc-devel
--
Michael H. Warfield (AI4NB) | (770) 978-7061 | mhw@xxxxxxxxxxxx
/\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/
NIC whois: MHW9 | An optimist believes we live in the best of all
PGP Key: 0x674627FF | possible worlds. A pessimist is sure of it!
Attachment:
signature.asc
Description: This is a digitally signed message part
