Dear all, why port 23? Was that a typo and you mean port 22 (ssh)?
All the best Jörg Am Donnerstag, 13. Juni 2019, 11:09:21 BST schrieb Robert G. Brown: > On Thu, 13 Jun 2019, Jonathan Engwall wrote: > > It was an actual machine I could ping but I could not connect. It was > > there > > at start up. > > If it is an actual machine, hang a console on it and see what is > happening. If you can ping it, its network is up. But to be able to > connect to it, you have to have a bunch of stuff configured to allow > connection. These problems all live at a higher level than the physical > transport levels. > > Personally, I'd start by killing selinux, as it is notorious for > nearly randomly deciding that this or that connection is not secure and > blocking it with no (EXTERNAL) warning -- it would show up in logs. If > you prefer, master selinux and figure out how to configure it for the > specific ports you are trying to connect to. Then I'd check the > firewall. Are you trying to ssh in? Make sure that port 23 is open and > not firewalled off in the default installation image. Then check > services. Are you trying to ssh in? Well, is sshd installed and > running? If it isn't, you have to install it, configure it, make sure > the firewall passes it, and make sure selinux isn't going to come in and > override the firewall and refuse to pass it after all. And so on, for > any port(s) you wish to access. Most linuxes these days install in a > default "secure" mode with no open ports and firewalled up pretty tight, > assuming that the installer is a normal human who has no idea how to > offer services or secure them, but if you run a cluster you really need > to be at least on the road to being an abnormal person who does. > > If you're trying to build a cluster that automagically installs with all > of this stuff up, well, then you'll need to read the manual(s) or > whatever documentation they provide to see what you didn't preconfigure > on the install host. > > Hopefully you're getting the idea that debugging networking problems > requires a) a pretty good knowledge of networking from the wire on up to > the network application; b) a pretty good knowledge of systems > administration and how to set up, start, manage, debug applications, > read logs (know where the logs are to read, for starters) etc; c) a very > patient and systematic approach. As Chris says, start at the wire up, > if it is wired, look at the wireless router tables of connected hosts if > it is wireless, etc. See if it pings. If it pings, see what's > wrong with the ports/services you're trying to connect to. Read logs. > Try experiments. Compare a working host to the one that isn't working. > Read the logs some more. > > It's all in there, if you know how to get it out. > > And again, if you really want our help, repost a DETAILED DESCRIPTION OF > WHAT IS WRONG. I'd wager 90% or more of the people on this list could > debug your problem from a sufficiently detailed description alone, but > so far we know next to nothing about what you are trying to do, what > your network looks like, what version of Linux (or other operating > system!) you are using, what tools you're talking about. I don't even > know if you are really trying to build or work with a cluster or are > just trying to figure out why ssh doesn't work out of the box on hosts > in an office. > > Details, please! > > rgb > > > On Tue, Jun 11, 2019, 9:49 PM Chris Samuel <ch...@csamuel.org> wrote: > > On 11/6/19 8:18 pm, Robert G. Brown wrote: > > > * Are these real hosts, each with their own network interface > > > > (wired or > > > > > wireless), or are these virtual hosts? > > > > In addendum to RGB's excellent advice and questions I would add > > to this > > question the network engineers maxim of "start at layer 1 and > > work up". > > > > In other words, first check your physical connectivity and then > > head up > > the layers. > > > > Best of luck! > > Chris > > -- > > ? Chris Samuel? :?http://www.csamuel.org/? :?Berkeley, CA, USA > > _______________________________________________ > > Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin > > Computing > > To change your subscription (digest mode or unsubscribe) visit > > https://beowulf.org/cgi-bin/mailman/listinfo/beowulf > > Robert G. Brown http://www.phy.duke.edu/~rgb/ > Duke University Dept. of Physics, Box 90305 > Durham, N.C. 27708-0305 > Phone: 1-919-660-2567 Fax: 919-660-2525 email:r...@phy.duke.edu > > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > https://beowulf.org/cgi-bin/mailman/listinfo/beowulf _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit https://beowulf.org/cgi-bin/mailman/listinfo/beowulf
