From: Gordon R. <drg...@gm...> - 2008-08-20 08:56:23
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I am wondering if anyone could offer me some advice on telnet access to the UML console. I run linuxzoo.net, which has very poor console access for users right now (it relies on network logins direct to the guests). Im trying to fix that... I am using something like "con1=port:5800". I have in.telnetd from a fedora install. I have port-helper. My problem is that the console connection seems unreliable in two ways. Firstly: If I connect and login, then press CTRL-D before terminating telnet, it works fine when I telnet in again. If I connect and login, but terminate telnet before CTRL-D, then when I telnet in again I get the login prompt but the keymapping seems broken. Key codes are either corrupt or the characters invisible. I cannot find any way to recover from this except a reboot of the guest. It is almost like the guest OS fails to reset the console line, or it is stuck in raw mode, or there is a process left from the last session messing the connection up... Secondly: I have an intermittent rare problem where sometimes I cannot connect after disconnecting. I get console messages "no one waiting for port". I may also be left with one in.telnetd zombie. The result is that sometimes I can never get in again. It is like the port helper thread has became 1 connection out of sync. I am using a guest based on 2.6.18. I was using 2.6.8 previously, and this has the same problem. I dont see anything in the uml changelog which would suggest a more modern kernel is a solution to this, but I could be wrong. All advice appreciated. Happy to try anything. I have been investigating this for a few months and I cannot come up with a good solution. I could drop back to fd consoles and writing my own telnetd server to access the file descriptors, but I would prefer not to reinvent the wheel. I know I could use "screen" but for security reasons I would prefer not to allow users to log into the host machines. Perhaps a different in.telnetd source would help? (any pointers to a good version)? Anyone tried in.telnetd using screen rather than login? Would more consoles associated with port:5800 help? Thanks Gordon. |
From: David F. R. P. <dav...@gm...> - 2008-08-20 20:40:25
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We have netkit-telnet-0.17 and it works fine but we use it, through a tuntap interface. The package comes from ftp://ftp.uk.linux.org/pub/linux/Networking/netkit David On Wed, Aug 20, 2008 at 1:56 AM, Gordon Russell <drg...@gm...>wrote: > I am wondering if anyone could offer me some advice on telnet access > to the UML console. > I run linuxzoo.net, which has very poor console access for users right > now (it relies on network logins direct to the guests). > Im trying to fix that... > > I am using something like "con1=port:5800". I have in.telnetd from a > fedora install. I have port-helper. > > My problem is that the console connection seems unreliable in two ways. > > Firstly: > If I connect and login, then press CTRL-D before terminating telnet, > it works fine when I telnet in again. > If I connect and login, but terminate telnet before CTRL-D, then when > I telnet in again I get the login prompt but the keymapping seems > broken. Key codes are either corrupt or the characters invisible. I > cannot find any way to recover from this except a reboot of the guest. > It is almost like the guest OS fails to reset the console line, or it > is stuck in raw mode, or there is a process left from the last session > messing the connection up... > > Secondly: > I have an intermittent rare problem where sometimes I cannot connect > after disconnecting. I get console messages "no one waiting for port". > I may also be left with one in.telnetd zombie. The result is that > sometimes I can never get in again. It is like the port helper thread > has became 1 connection out of sync. > > I am using a guest based on 2.6.18. I was using 2.6.8 previously, and > this has the same problem. I dont see anything in the uml changelog > which would suggest a more modern kernel is a solution to this, but I > could be wrong. > > All advice appreciated. Happy to try anything. I have been > investigating this for a few months and I cannot come up with a good > solution. I could drop back to fd consoles and writing my own telnetd > server to access the file descriptors, but I would prefer not to > reinvent the wheel. I know I could use "screen" but for security > reasons I would prefer not to allow users to log into the host > machines. > Perhaps a different in.telnetd source would help? (any pointers to a > good version)? > > Anyone tried in.telnetd using screen rather than login? > Would more consoles associated with port:5800 help? > > Thanks > Gordon. > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's > challenge > Build the coolest Linux based applications with Moblin SDK & win great > prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > User-mode-linux-user mailing list > Use...@li... > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user > |
From: Gordon R. <drg...@gm...> - 2008-08-21 10:41:17
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Thanks for the link. I will give that telnet server a go and see if it is any different. Just to let you know, I do currently allow users to access their guests via a tap device, and in general it works really well. However, some of my practical exercises get the users to configure their own firewalls, and since they are just learning it turns out to be easy for them to deny their own connection. Thus a console interface would be most useful. Thanks for the suggestion. Gordon. 2008/8/20 David Francisco Rodriguez Perez <dav...@gm...>: > We have netkit-telnet-0.17 and it works fine but we use it, through a tuntap > interface. > The package comes from > ftp://ftp.uk.linux.org/pub/linux/Networking/netkit |
From: Jeff D. <jd...@ad...> - 2008-08-27 16:36:22
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On Wed, Aug 20, 2008 at 09:56:20AM +0100, Gordon Russell wrote: > Firstly: > If I connect and login, then press CTRL-D before terminating telnet, > it works fine when I telnet in again. > If I connect and login, but terminate telnet before CTRL-D, then when > I telnet in again I get the login prompt but the keymapping seems > broken. Key codes are either corrupt or the characters invisible. I > cannot find any way to recover from this except a reboot of the guest. > It is almost like the guest OS fails to reset the console line, or it > is stuck in raw mode, or there is a process left from the last session > messing the connection up... > Secondly: > I have an intermittent rare problem where sometimes I cannot connect > after disconnecting. I get console messages "no one waiting for port". > I may also be left with one in.telnetd zombie. The result is that > sometimes I can never get in again. It is like the port helper thread > has became 1 connection out of sync. > > I am using a guest based on 2.6.18. I was using 2.6.8 previously, and > this has the same problem. I dont see anything in the uml changelog > which would suggest a more modern kernel is a solution to this, but I > could be wrong. I check this on a fairly regular basis, and haven't seen this happen in a long time. Can you check something recent? 2.6.18 is fairly old, and there has been work in that area since then. > All advice appreciated. Happy to try anything. I have been > investigating this for a few months and I cannot come up with a good > solution. I could drop back to fd consoles and writing my own telnetd > server to access the file descriptors, but I would prefer not to > reinvent the wheel. I know I could use "screen" but for security > reasons I would prefer not to allow users to log into the host > machines. > Perhaps a different in.telnetd source would help? (any pointers to a > good version)? The other thing you could try, which I think is somewhat preferable, is to set up another UML which is used as a console server: your users get normal user accounts in this UML to which they log in over the net there is a virtual serial line between a device in this new UML and each of the others users can run screen /dev/pts/whatever to get access to the console on their UMLs If you have the UML book, it describes in detail how to set this up. Jeff -- Work email - jdike at linux dot intel dot com |
From: Gordon R. <drg...@gm...> - 2008-09-23 19:05:51
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>> I have an intermittent rare problem where sometimes I cannot connect >> after disconnecting. I get console messages "no one waiting for port". >> I am using a guest based on 2.6.18. > > I check this on a fairly regular basis, and haven't seen this happen > in a long time. Can you check something recent? I upgraded to 2.6.26 (I thought I would stick with the even numbered kernels). I have not been able to reproduce the problem. I also started updating my servers to 64 bits. Only difference I notice is that there are many more processes than I am used to in SKAS3 (I am using SKAS0 for 64 bit without /proc/mm). It is early days but everything it seems to be working great! Keep up the good work. Gordon. |