Ah this is a unix command. yeah it exists in slackware too. Didn't think of this. Still is there a way (that you know of) to prioritize ipv4 over ipv6 ? for example I read that /etc/hosts file can lead to ipv6 resolution with priority if the ::1 entry is above the 127.0.0.1 one. But this is not the case in my case.
Alternatively, is it possible to tell the X server to prefer ipv4 over ipv6 ? On Tue, Jan 20, 2026 at 10:43 AM Ulrich Sibiller <[email protected]> wrote: > Hi, > > well, of course IPv4 should suffice. Maybe you should check if your > name resolution yields IPv6 addresses. No idea how slackware handles > this but there should be a straightforward way to disable IPv6. Using > firewall rules seems wrong to me. > > In RedHat you can do this using sysctl and set > "net.ipv6.conf.all.disable_ipv6 = 1". > > Uli > > On Mon, Jan 19, 2026 at 11:23 PM Athanasios Silis > <[email protected]> wrote: > > > > Ok I have figured it out, but I don't think it should be like that. > > > > So I have completely disabled ipv6 on that laptop (policy is DROP for > all chains INPUT, OUTPUT and FORWARD). No it did not even accept localhost > connections in ipv6. > > Once I changed the firewall to accept local ipv6 connections (accept > from localhost only and accept OUTgoing packets in output chain) things > started working again. > > > > The question is. Shouldn't ipv4 suffice for all this to work ? > > > > This question has no practical value but I would very much like to > understand why does ipv6 must be allowed internally. > > > > Thank you for your help Ulrich! > > > > > > On Mon, Jan 19, 2026 at 11:03 PM Athanasios Silis < > [email protected]> wrote: > >> > >> hi Ulrich, > >> thank you for the quick response. > >> Definitely X11 systems across all the systems I admin - no wayland. > >> > >> The quick test does indeed create an nxagent window . It does delay > unreasonably though for about 10seconds at some point. > >> Eventually it does continue and I do see the black/empty window > eventually. You'll notice that the nxagent on the server side is > (thankfully) Version 3.5.99.26. > >> Please note: the x2goserver resides on a slackware64-current system. > But I have another reference system (slackware64-15.0) with the exact same > x2goserver version. > >> The reference version works fine and running the same test there works > fine too, but it does not "halt" at the moment when the problematic halts > for about 10 seconds. > >> > >> OK so the log in the problematic system is as follows: > >> > >> nass@whitestar$ ssh blackstar -X > >> Last login: Mon Jan 19 22:37:27 2026 from 192.168.112.145 > >> Linux 6.12.63. > >> > >> nass@blackstar:~$ nxagent :55 > >> > >> NXAGENT - Version 3.5.99.26 > >> > >> Copyright (c) 2001, 2011 NoMachine (http://www.nomachine.com) > >> Copyright (c) 2008-2014 Oleksandr Shneyder <[email protected]> > >> Copyright (c) 2011-2016 Mike Gabriel <[email protected]> > >> Copyright (c) 2014-2016 Ulrich Sibiller <[email protected]> > >> Copyright (c) 2014-2016 Mihai Moldovan <[email protected]> > >> Copyright (c) 2015-2016 Qindel Group (http://www.qindel.com) > >> See https://github.com/ArcticaProject/nx-libs for more information. > >> > >> Info: Agent running with pid '17964'. > >> Session: Starting session at 'Mon Jan 19 22:49:53 2026'. > >> > >> [It seemingly blocks for about 10seconds here. Then it continues...] > >> > >> Info: Using alpha channel in render extension. > >> Info: Not using local device configuration changes. > >> Warning: Cannot read keystroke file > '/home/nass/.nx/config/keystrokes.cfg'. > >> Info: using keystrokes file '/etc/nxagent/keystrokes.cfg' > >> Currently known keystrokes: > >> close_session : Ctrl+Alt+t > >> switch_all_screens : Ctrl+Alt+f > >> fullscreen : Ctrl+Shift+Alt+f > >> minimize : Ctrl+Alt+m > >> defer : Ctrl+Alt+e > >> force_synchronization : Ctrl+Alt+j > >> resize : Ctrl+Alt+r > >> viewport_move_left : Ctrl+Shift+Alt+Left > >> viewport_move_left : Ctrl+Shift+Alt+KP_Left > >> viewport_move_up : Ctrl+Shift+Alt+Up > >> viewport_move_up : Ctrl+Shift+Alt+KP_Up > >> viewport_move_right : Ctrl+Shift+Alt+Right > >> viewport_move_right : Ctrl+Shift+Alt+KP_Right > >> viewport_move_down : Ctrl+Shift+Alt+Down > >> viewport_move_down : Ctrl+Shift+Alt+KP_Down > >> viewport_scroll_left : Ctrl+Alt+Left > >> viewport_scroll_left : Ctrl+Alt+KP_Left > >> viewport_scroll_up : Ctrl+Alt+Up > >> viewport_scroll_up : Ctrl+Alt+KP_Up > >> viewport_scroll_right : Ctrl+Alt+Right > >> viewport_scroll_right : Ctrl+Alt+KP_Right > >> viewport_scroll_down : Ctrl+Alt+Down > >> viewport_scroll_down : Ctrl+Alt+KP_Down > >> reread_keystrokes : Ctrl+Alt+k > >> autograb : Ctrl+Alt+g > >> dump_clipboard : Ctrl+Shift+Alt+c > >> error opening security policy file /usr/local/share/nx/SecurityPolicy > >> Info: Keycode conversion auto-determined as on > >> Session: Session started at 'Mon Jan 19 22:50:04 2026'. > >> Info: Screen [0] resized to geometry [1280x965] fullscreen [0]. > >> > >> At this stage the nxagent window fired up in the server side, has been > drawn in the client desktop environment as a separate window. > >> > >> > >> > >> > >> On Mon, Jan 19, 2026 at 9:42 PM Ulrich Sibiller < > [email protected]> wrote: > >>> > >>> Hi, > >>> > >>> You are using nxproxy 3 > >>> 5.99.23 which should not be a problem, despite being very old. But > maybe you are also using this ancient version on the server. Which IS a > problem. Please ensure you use 3.5.99.26 or 27. > >>> > >>> A quick test to rule out some things: ssh -X ro the server, then run > nxagent :55. Do you see an nxagent window? > >>> > >>> Also, are you sure you have an X desktop running on the server and not > wayland? And on the client? > >>> > >>> Uli > >>> > >>> > >>> > >>> Athanasios Silis <[email protected]> schrieb am Mo., 19. > Jan. 2026, 19:34: > >>>> > >>>> Hi all, > >>>> I recently installed x2goserver (and x2goclient but this is probably > not relevant in this case) on a fresh slackware-current system. > >>>> > >>>> Then, using x2goclients from other computers (other slackware64-15.0, > ubuntu20.04 and 24.04 and debian systems) I want to "fetch" a desktop from > this fresh system to one of the other client systems. > >>>> > >>>> The connection seems to go through normally but I never see a desktop > window poping up. I have tried "xfce" and "fluxbox" (as a custom command) > both of which have been faithfully working in the past and in other > installations. > >>>> > >>>> I used `x2goclient --debug` to invoke the session and see if there > are any meaningful messages error messages from the client side, but I have > not been able to figure out if there is anything relevant: > >>>> > >>>> $ x2goclient --debug > >>>> qt5ct: using qt5ct plugin > >>>> x2go-INFO-1> "Starting X2Go Client 4.1.2.2..." > >>>> [...] > >>>> x2go-INFO-3> "Started X2Go Client." > >>>> [...] > >>>> x2go-INFO-8> "Starting connection to server: x.x.x.x:22" > >>>> [...] > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:687> User > authentication OK. > >>>> [...] > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:702> Login Check - OK > >>>> x2go-DEBUG-../src/onmainwindow.cpp:2947> SSH connection > established. > >>>> x2go-DEBUG-../src/onmainwindow.cpp:3374> Continue normal X2Go > session > >>>> [...] > >>>> x2go-DEBUG-../src/sshprocess.cpp:387> Starting tunnel via > SshProcess object 2: "localhost":57842 -> "localhost":58842 > >>>> [...] > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2065> Executing remote: > "bash -l -c 'echo \"X2GODATABEGIN:1790db9f-7b15-48ca-9eec-7596bdb1cccf\"; > export PATH=\"/usr/local/bin:/usr/bin:/bin\";export TERM=\"dumb\"; > X2GODPI=141 X2GO_XINERAMA=no x2gostartagent 800x600 adsl 16m-jpeg-9 > unix-kde-depth_24 us auto 1 D startfluxbox both; echo > \"X2GODATAEND:1790db9f-7b15-48ca-9eec-7596bdb1cccf\";'" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:6142> "Starting NX proxy, > command: nxproxy -S > nx/nx,options=/home/user/.x2go/S-poker-50-1768844727_stDstartfluxbox_dp24/options:50" > >>>> [...] > >>>> x2go-DEBUG-../src/onmainwindow.cpp:6618> Proxy wrote on stderr: > "\nNXPROXY - Version 3.5.99.23\n\nCopyright (c) 2001, 2011 NoMachine[...] > >>>> Info: Connecting to remote host 'localhost:58842'.\n > >>>> Info: Connected to remote proxy on FD#5.\n" > >>>> > >>>> > >>>> So it seems ssh connection gets established, login is OK, > `nxstartagent` is executed fine, and `nxproxy` also starts without errors. > but then > >>>> > >>>> > >>>> > >>>> 2go-DEBUG-../src/sshprocess.cpp:109> New TCP connection. > >>>> x2go-DEBUG-../src/sshprocess.cpp:114> New socket: 21 > >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy > window: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with > title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1977> Creating new > channel. > >>>> > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1990> New > channel:0x7f5b580102e0 > >>>> > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1994> Forwarding > parameters: from remote ("localhost":57842) to local ("localhost":35710) > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2028> Temporary session > port after config file parse: 57842 > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2032> Temporary session > host after config file parse: localhost > >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy > window: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with > title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy > window: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with > title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy > window: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with > title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> [...] > >>>> x2go-DEBUG-../src/onmainwindow.cpp:6618> Proxy wrote on stderr: > "Info: Aborting the procedure due to signal '15'.\nSession: Session > terminated at 'Mon Jan 19 19:46:53 2026'.\n" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:6475> Deleting Proxy. > >>>> x2go-DEBUG-../src/onmainwindow.cpp:6520> Waiting for proxy to > exit. > >>>> x2go-DEBUG-../src/onmainwindow.cpp:6544> Checking exit status. > >>>> x2go-DEBUG-../src/sshprocess.cpp:199> Executing remote command > via SshProcess object 3: "x2gocmdexitmessage > nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/sshprocess.cpp:213> > this=SshProcess(0x55f9bbed6c50) Running > masterCon->addChannelConnection(this, > '"475b1d25-5fe0-4e44-abcc-dea30df785f1"', '"bash -l -c 'echo > \"X2GODATABEGIN:475b1d25-5fe0-4e44-abcc-dea30df785f1\"; export > PATH=\"/usr/local/bin:/usr/bin:/bin\";export TERM=\"dumb\"; > x2gocmdexitmessage nass-50-1768844727_stDstartfluxbox_dp24; echo \""'); > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:1810> Locking SSH > channel connection MUTEX. > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2055> > "ssh_channel_open_forward failed": "No channel request of this type from > server" > >>>> > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2187> > "ssh_channel_write failed": "Remote channel is closed" > >>>> > >>>> then it tries to resume > >>>> > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2065> Executing remote: > "bash -l -c 'echo \"X2GODATABEGIN:a6aca35a-a72c-4453-96b1-0a2e1b49dfcb\"; > export PATH=\"/usr/local/bin:/usr/bin:/bin\";export TERM=\"dumb\"; > x2goresume-session nass-50-1768844727_stDstartfluxbox_dp24 800x600 adsl > 16m-jpeg-9 us auto 1 both no; echo > \"X2GODATAEND:a6aca35a-a72c-4453-96b1-0a2e1b49dfcb\";'" > >>>> > >>>> x2go-DEBUG-../src/sshmasterconnection.cpp:2071> > "ssh_channel_open_session failed": "Socket error: Success" > >>>> > >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy > window: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with > title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: > "ssh_channel_open_forward failed."" - No channel request of this type from > server" (2). > >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: > "ssh_channel_write failed."" - Remote channel is closed" (2). > >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: > "ssh_channel_open_session failed."" - Received SSH_MSG_DISCONNECT: 2:oclose > packet referred to nonexistent channel 0" (3). > >>>> x2go-DEBUG-../src/sshprocess.cpp:478> I/O error: > "ssh_channel_open_session failed."" - Socket error: Success" (4). > >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy > window: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with > title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:11659> "Searching proxy > window: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> x2go-DEBUG-../src/onmainwindow.cpp:13278> "Searching window with > title: X2GO-nass-50-1768844727_stDstartfluxbox_dp24" > >>>> > >>>> and afterwards I get the last 2 messages in an endless loop. No > desktop window pops up. > >>>> > >>>> > >>>> I am also very confused about the > >>>> > >>>> "ssh_channel_open_session failed": "Socket error: Success" > >>>> > >>>> > >>>> I have not found any information about how to enable debug output in > the server side (only on the client side) and the current messages do not > give me a clear view as to what is wrong. > >>>> > >>>> Do you have any idea which way I should look next? > >>>> > >>>> Thank you in advance for your help. > >>>> > >>>> > >>>> _______________________________________________ > >>>> x2go-user mailing list -- [email protected] > >>>> To unsubscribe send an email to [email protected] > >>>> ${mailinglist_url} (substitution broken, will need mailman upgrade) > >>>> https://lists.x2go.org/postorius/lists/x2go-user.lists.x2go.org >
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