[petsc-users] osx error

Mark Adams mfadams at lbl.gov
Fri Sep 18 10:04:24 CDT 2020 

On Fri, Sep 18, 2020 at 10:23 AM Barry Smith <bsmith at petsc.dev> wrote:

>
>   This email thread doesn't seem to have clear communication. Can we start
> at the beginning again please? Please answer my questions directly in the
> appropriate lines below in your email response so we know what answer goes
> with what question. I know you have done some of these things but it is
> unclear what order you did them and the order is important.
>
>   Background: In order to decide if the test in MPI.py works, or needs to
> be modified or removed we need clear information about your system BEFORE
> you made changes to get things to work.
>
>    1) Did you add the
>
>    127.0.0.1    MarksMac-5.local
>
>     to the /etc/hosts yesterday because Satish suggested it, or have you
> had it there for a long time? (You should not need it)
>

Satish suggested MarksMac-302.local.

As I said earlier I have seen messages that say something like a network
problem, renaming hostname to MarksMac-X.local, where X is +1 the current
X. Initially it was MarksMac.local and it made MarksMac-1.local


>    2) Please run
>
>         ping -c 2 `hostname`
>

09:08 master *= ~/Codes/petsc$ ping -c 2 `hostname`
PING marksmac-302.local (127.0.0.1): 56 data bytes
Request timeout for icmp_seq 0

--- marksmac-302.local ping statistics ---
2 packets transmitted, 0 packets received, 100.0% packet loss
10:55 2 master *= ~/Codes/petsc$


>
>    3) Please remove the line 127.0.0.1    MarksMac-5.local in /etc/hosts
> and follow the directions in
>
>
> https://stackoverflow.com/questions/37951379/etc-hosts-ignored-in-mac-el-capitan-10-11-5
>
>       to flush the DNS cache (note for different versions of MacOS the
> command is different).
>

My takeway here was you need one space between the IP and name. I had a tab
here:

127.0.0.1 localhost

fixed, but did not help. Its not clear to me what you want me to do. He did
two scary (sudo goop) things. One was:

sudo launchctl unload -w
/System/Library/LaunchDaemons/com.apple.mDNSResponder.plist

Do you want me to do that?


>
>   4) Please run
>
>       ping -c 2 `hostname`
>
>    5) Please run a MPI program (doesn't matter which and I don't care how
> you installed MPICH or OpenMPI) with
>
>      mpiexec -n 2 ./programname
>
>      does it run, hang or ?
>
>
>   Based on this information we can decide what needs to be done next.
>
>   Thanks
>
>     Barry
>
> As a side note on my Mac
>
> $ hostname
> Barrys-MacBook-Pro-3.local
> ~/Src/petsc* (barry/2020-07-07/docs-no-makefiles *>)*
> arch-docs-no-makefiles
> $ /sbin/ping -c 2 `hostname`
> PING barrys-macbook-pro-3.local (127.0.0.1): 56 data bytes
> 64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=0.077 ms
> 64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.112 ms
>
> --- barrys-macbook-pro-3.local ping statistics ---
> 2 packets transmitted, 2 packets received, 0.0% packet loss
> round-trip min/avg/max/stddev = 0.077/0.095/0.112/0.018 ms
> ~/Src/petsc* (barry/2020-07-07/docs-no-makefiles *>)*
> arch-docs-no-makefiles
> $
>
> We are trying to understand if/why your machine is behaving differently.
>
> My theory is that if ping -c 2 `hostname` fails then MPICH and OpenMP
> mpiexec -n 2 will fail. We need to determine if this theory is correct or
> if you have a counter-example.
>
>
> On Sep 18, 2020, at 8:09 AM, Mark Adams <mfadams at lbl.gov> wrote:
>
>
>
> On Fri, Sep 18, 2020 at 7:51 AM Matthew Knepley <knepley at gmail.com> wrote:
>
>> On Fri, Sep 18, 2020 at 7:46 AM Mark Adams <mfadams at lbl.gov> wrote:
>>
>>> Oh you did not change my hostname:
>>>
>>> 07:37 master *= ~/Codes/petsc$ hostname
>>> MarksMac-302.local
>>> 07:41 master *= ~/Codes/petsc$ ping -c 2 MarksMac-302.local
>>> PING marksmac-302.local (127.0.0.1): 56 data bytes
>>> Request timeout for icmp_seq 0
>>>
>>> --- marksmac-302.local ping statistics ---
>>> 2 packets transmitted, 0 packets received, 100.0% packet loss
>>> 07:42 2 master *= ~/Codes/petsc$
>>>
>>
>> This does not make sense to me. You have
>>
>>   127.0.0.1 MarksMac-302.local
>>
>> in /etc/hosts,
>>
>
> 09:07  ~/.ssh$ cat /etc/hosts
> ##
> # Host Database
> #
> # localhost is used to configure the loopback interface
> # when the system is booting.  Do not change this entry.
> ##
> 127.0.0.1 localhost
> 255.255.255.255 broadcasthost
> 127.0.0.1    MarksMac-5.local
> 127.0.0.1 243.124.240.10.in-addr.arpa.private.cam.ac.uk
> 127.0.0.1 MarksMac-302.local
> 09:07  ~/.ssh$
>
>
>
>
>
>> but you cannot resolve that name?
>>
>>   Matt
>>
>>
>>> BTW, I used to get messages about some network issue and 'changing host
>>> name to MarksMac-[x+1].local'. That is, the original hostname
>>> was MarksMac.local, then I got a message about changing
>>> to MarksMac-1.local, etc. I have not seen these messages for months but
>>> apparently this process has continued unabated.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Thu, Sep 17, 2020 at 11:10 PM Satish Balay via petsc-users <
>>> petsc-users at mcs.anl.gov> wrote:
>>>
>>>> On Thu, 17 Sep 2020, Matthew Knepley wrote:
>>>>
>>>> > On Thu, Sep 17, 2020 at 8:33 PM Barry Smith <bsmith at petsc.dev> wrote:
>>>> >
>>>> > > > On Sep 17, 2020, at 4:59 PM, Satish Balay via petsc-users <
>>>> > > petsc-users at mcs.anl.gov> wrote:
>>>> > > >
>>>> > > > Here is a fix:
>>>> > > >
>>>> > > > echo 127.0.0.1 `hostname` | sudo tee -a /etc/hosts
>>>> > >
>>>> > >  Satish,
>>>> > >
>>>> > >    I don't think you want to be doing this on a Mac (on anything?)
>>>> On a
>>>> > > Mac based on the network configuration etc as it boots up and as
>>>> networks
>>>> > > are accessible or not (wi-fi) it determines what hostname should
>>>> be, one
>>>> > > should never being hardwiring it to some value.
>>>> > >
>>>> >
>>>> > Satish is just naming the loopback interface. I did this on all my
>>>> former
>>>> > Macs.
>>>>
>>>>
>>>> Yes - this doesn't change the hostname. Its just adding an entry for
>>>> gethostbyname - for current hostname.
>>>>
>>>> >>>
>>>> 127.0.0.1 MarksMac-302.local
>>>> <<<
>>>>
>>>> Sure - its best to not do this when one has a proper IP name [like
>>>> foo.mcs.anl.gov] - but its useful when one has a hostname like
>>>> "MarksMac-302.local" -that is not DNS resolvable
>>>>
>>>> Even if the machine is moved to a different network with a different
>>>> name - the current entry won't cause problems [but will need another entry
>>>> for the new host name - if this new name is also not DNS resolvable]
>>>>
>>>> Its likely this file is a generated file on  macos  - so might get
>>>> reset on reboot - or some network change? [if this is the case - the change
>>>> won't be permanent]
>>>>
>>>>
>>>> Satish
>>>>
>>>
>>
>> --
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which their
>> experiments lead.
>> -- Norbert Wiener
>>
>> https://www.cse.buffalo.edu/~knepley/
>> <http://www.cse.buffalo.edu/~knepley/>
>>
>
>
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