[ClusterLabs] fence agent and using it with pacemaker

[Dejan Muhamedagic]

Hi,

On Thu, Feb 11, 2016 at 03:56:15PM +0100, Stanislav Kopp wrote:
> HI again,
> 
> I think I've sorted it out, correct me if I'm wrong.
> 
> - "fence-agents" are RHCS compatible fence agents (for using with
> RGmanager originally?) located in /usr/sbin/fence_*,

Yes.

> - "cluster-glue" provides agents compatible with pacemaker, they re
> located in "/usr/lib/stonith/plugins/"

Right. But today pacemaker supports both. I don't recall anymore
with which release support for fencing agents was introduced. The
support is compile-time and RHEL includes support for only
fencing agents, whereas most other distributions include support
for both.

> "fence_pve" [1] agent looks like RHCS agent, so it doesn't work
> out-of-box with pacemaker, but like Dejan hints, it's possible to use
> rhcs "adapter" to use RH fencing agent in pacemaker. Unfortunally I
> don't have
> 
> /usr/lib{,64}/stonith/plugins/rhcs directory in Debian (only rhcs.so
> lib), can't find it via "yum provides" in Centos 7 either.

You won't find it in Centos or RHEL.

> Is there some documentation how to use RHCS fence agent with pacemaker
> esp. with crmsh examples?

Well, no, but it should be easy. You just create that directory
and then create a link to your fencing agent:

# mkdir /usr/lib{,64}/stonith/plugins/rhcs
# cd /usr/lib{,64}/stonith/plugins/rhcs
# ln -s /usr/sbin/fence_pve

Thanks,

Dejan

> 
> Best,
> Stan
> 
> [1] https://github.com/ClusterLabs/fence-agents/blob/master/fence/agents/pve/fence_pve.py
> 
> 2016-02-11 12:07 GMT+01:00 Stanislav Kopp <staskopp at gmail.com>:
> > HI Dejan,
> >
> > 2016-02-10 20:28 GMT+01:00 Dejan Muhamedagic <dejanmm at fastmail.fm>:
> >> Hi,
> >>
> >> On Wed, Feb 10, 2016 at 03:20:49PM +0100, Stanislav Kopp wrote:
> >>> Hi all,
> >>>
> >>> I have general, clarification question about how fence agents work
> >>> with pacemaker (crmsh in particular). As far I understood STDIN
> >>
> >> Not sure what crmsh has to do with fencing agents. The
> >> interaction happens between other pacemaker components (normally
> >> stonithd) and the agent.
> >
> > I've mentioned crm, to make sure it's not some stupid syntax error by
> > me with stonith definition.
> >
> >>> arguments can be used within pacemaker resources and command line
> >>> arguments in terminal (for testing and scripting?).
> >>
> >> As for testing, crmsh has support for resource testing with
> >> 'configure rsctest', but apparently only Linux HA stonith agents
> >> (legacy*) are currently supported.
> >>
> >> Otherwise, there's stonith_admin(8) and stonith(8) for stonith
> >> agents. The former uses stonith-ng (stonithd) which makes it
> >> closer to the real cluster operation.
> >>
> >> There is also a (not so well known) stonith interface to fencing
> >> agents, which predates RH fencing agents support in pacemaker.
> >> One just needs to create a link in /usr/lib64/stonith/plugins/rhcs:
> >
> > That sounds interesting, because the agent (fence_pve) comes with
> > "fence-agents" package, and not with "cluster-glue" (in Debian), Do
> > you know, what is difference between agents in /usr/sbin/ (like
> > "/usr/sbin/fence_ilo") and in "/usr/lib/stonith/plugins/external/"?
> >
> > Thanks,
> > Stan
> >
> >> lrwxrwxrwx 1 root root 32 Nov 18 07:56 fence_cisco_ucs -> ../../../../sbin/fence_cisco_ucs
> >>
> >> For instance, this agent is referenced as stonith:rhcs/cisco_ucs.
> >>
> >> Finally, it would be great to somehow put together the two
> >> fencing/stonith agents sets.
> >>
> >> Thanks,
> >>
> >> Dejan
> >>
> >> *) Why the Linux HA stonith agents got the attribute/name
> >> "legacy" in Pacemaker at some point is beyond me.
> >>
> >>> I have "fence_pve" [1] agent which works fine with command line
> >>> arguments, but not with pacemaker, it says some parameters like
> >>> "passwd" or "login" does not exist, although STDIN parameters are
> >>> supported [2]
> >>>
> >>> I'm using  stock 1.1.7-1 on Debian Wheezy
> >>>
> >>> Best,
> >>> Stan
> >>>
> >>>
> >>> [1] https://github.com/ClusterLabs/fence-agents/blob/master/fence/agents/pve/fence_pve.py
> >>> [2] https://www.mankier.com/8/fence_pve#Stdin_Parameters
> >>>
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