[ale] ssh question [solved]
Michael H. Warfield
mhw at WittsEnd.com
Thu May 10 11:47:25 EDT 2012
On Thu, 2012-05-10 at 11:22 -0400, Richard Bronosky wrote:
> Does this mean that another solution could have been this?
> ssh hostname "etc/init.d/service restart; echo;"
> Good to know. I didn't know of that behavior.
Just simply doing an echo might well have worked, but I would have to
try it to tell. I know for sure, it can be avoided using "nohup" but
then you don't get your regular output, so that's not an ideal situation
either. If you were to use pipes (|) vs semi (;) it could also affect
the behavior. Every time I run into it, I play around with different
solutions until I find the one I like the best.
I originally learned about this because I was the maintainer for smbfs /
smbmount / smbmnt from the Samba team. That was tripping over the same
problem because smbmnt would go daemon and leave open file descriptors
and cause this hang. I think it was even Marcus that explained the
reasoning for the problem to me and what some of the solutions were.
But smbfs has been deprecated for years (replaced by cifs and cifsmount)
so I can tell you this has been around for a lllooonnnggg time.
Regards,
Mike
> On Thu, May 10, 2012 at 9:40 AM, Michael H. Warfield <mhw at wittsend.com> wrote:
> > On Thu, 2012-05-10 at 08:27 -0400, Edward Holcroft wrote:
> >> This is what worked:
> >
> >> $ sshpass -p '1qazxsw2' ssh -o StrictHostKeyChecking=no -t
> >> root at 192.168.50.87 "/etc/init.d/asterisk restart; sleep 5; exit"
> >
> > The problem you've run into is an old one that been known and discussed
> > for a long time. What happens is that sshd will not exit until all the
> > fds are closed, not just that the child has exited. This is intended to
> > insure that any buffered IO has been passed back to the client before
> > terminating the server end. What has happened is that your "asterisk
> > restart" process has forked off a daemon (asterisk service) that has not
> > closed stdout and stderr so sshd hangs around even though the script is
> > done. By running the commands the way you did in your "solution", you
> > run an extra shell to handle the chain of commands with an explicit
> > exit. There are several different ways of handling it, all with their
> > pluses and minuses.
> >
> > The behavior was discussed over on the OpenSSH forums quite some time
> > ago and debate invariable boils down to the conclusion - "works by
> > design - not a bug - will not fix". They blame it on the daemon
> > processes which did not close out their stdout and stderr fds when they
> > forked off the daemon process.
> >
> > Regards,
> > Mike
> >
> >> On Thu, May 10, 2012 at 7:59 AM, Edward Holcroft <eholcroft at mkainc.com>wrote:
> >>
> >> > Morning all
> >> >
> >> > I need to run a command on an internal server that will restart a given
> >> > service, in this case asterisk, without user intervention. I using this:
> >> >
> >> > sshpass -p '1qazxsw2' ssh -o StrictHostKeyChecking=no root at 192.168.50.87/etc/init.d/asterisk restart
> >> >
> >> > The problem is this command never logs out:
> >> >
> >> > Stopping safe_asterisk: [ OK ]
> >> > Shutting down asterisk: [ OK ]
> >> > Starting asterisk: [ OK ]
> >> >
> >> > .... and there it sits, until I manually close it
> >> >
> >> > I also tried using -t with the ssh command, which closes the session, but
> >> > without restarting the service, even though it says it did:
> >> >
> >> > $ sshpass -p '1qazxsw2' ssh -o StrictHostKeyChecking=no -t
> >> > root at 192.168.50.87 "/etc/init.d/asterisk restart"
> >> > Stopping safe_asterisk: [FAILED]
> >> > Shutting down asterisk: [FAILED]
> >> > Starting asterisk: [ OK ]
> >> > Connection to 192.168.50.87 closed.
> >> >
> >> > I found this article:
> >> >
> >> > http://www.snailbook.com/faq/background-jobs.auto.html
> >> >
> >> > And tried:
> >> >
> >> > $ sshpass -p '1qazxsw2' ssh -o StrictHostKeyChecking=no root at 192.168.50.87/etc/init.d/asterisk restart < /dev/null
> >> >
> >> > which also does not close.
> >> >
> >> > Any ideas on how I can get this to run the way I want it to?
> >> >
> >> > ed
> >> > --
> >> > Edward Holcroft
> >> > Madsen Kneppers & Associates Inc.
> >> > 3020 Holcomb Bridge Rd. NW
> >> > Norcross, GA
> >> > 30071
> >> > Tel (770) 446-9606
> >> > GoogleVoice (678) 587-8649
> >> >
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> >> >
> >>
> >>
> >>
> >> --
> >> Edward Holcroft
> >> Madsen Kneppers & Associates Inc.
> >> 3020 Holcomb Bridge Rd. NW
> >> Norcross, GA
> >> 30071
> >> Tel (770) 446-9606
> >> GoogleVoice (678) 587-8649
> >>
> >> WARNING/CONFIDENTIALITY NOTICE:This message may be confidential and/or
> >> privileged. If you are not the intended recipient, please notify the sender
> >> immediately then delete it - you should not copy or use it for any purpose
> >> or disclose its content to any other person. Internet communications are
> >> not secure. You should scan this message and any attachments for viruses.
> >> Any unauthorized use or interception of this e-mail is illegal.
> >>
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> > --
> > Michael H. Warfield (AI4NB) | (770) 985-6132 | mhw at WittsEnd.com
> > /\/\|=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!
> >
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>
>
> --
> .!# RichardBronosky #!.
>
--
Michael H. Warfield (AI4NB) | (770) 985-6132 | mhw at WittsEnd.com
/\/\|=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!
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