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I have a simple openssh server running in a Alpine Linux 3.15 Docker container, and a client, also running on another Docker container (same version of Alpine of the server) that runs a X server with dwm

The client is able to open a graphical application (st) through X11 forwarding from the server to the client display, the problem is that i can only open a single instance of st before receiving the following error:

ssh: connect to host 172.17.0.2 port 22: Connection refused

server-side log:

Starting session: command on pts/1 for client from 172.17.0.3 port 34060 id 0
debug1: Setting controlling tty using TIOCSCTTY.
debug1: X11 connection requested.
debug1: channel 3: new [X11 connection from 172.17.0.2 port 35028]
debug1: Received SIGCHLD.
debug1: session_by_pid: pid 9
debug1: session_exit_message: session 0 channel 0 pid 9
debug1: session_exit_message: release channel 0
debug1: session_by_tty: session 0 tty /dev/pts/1
debug1: session_pty_cleanup2: session 0 release /dev/pts/1
debug1: channel 3: free: X11 connection from 172.17.0.2 port 35028, nchannels 4
debug1: session_by_channel: session 0 channel 0
debug1: session_close_by_channel: channel 0 child 0
debug1: session_close_x11: detach x11 channel 1
debug1: session_close_x11: detach x11 channel 2
Close session: user client from 172.17.0.3 port 34060 id 0
debug1: channel 0: free: server-session, nchannels 3
debug1: channel 1: free: X11 inet listener, nchannels 2
debug1: channel 2: free: X11 inet listener, nchannels 1
Received disconnect from 172.17.0.3 port 34060:11: disconnected by user
Disconnected from user client 172.17.0.3 port 34060
debug1: do_cleanup
debug1: do_cleanup

client-side log:

Running /usr/bin/xauth remove ssh:10.0
/usr/bin/xauth add ssh:10.0 MIT-MAGIC-COOKIE-1 49907415ff518044198f6f0075f270fe
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 172.17.0.2 35028
debug1: channel 1: new [x11]
debug1: confirm x11
OpenSSH_8.8p1, OpenSSL 1.1.1l  24 Aug 2021
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
debug1: Connecting to 172.17.0.2 [172.17.0.2] port 22.
debug1: connect to address 172.17.0.2 port 22: Connection refused
ssh: connect to host 172.17.0.2 port 22: Connection refused
xinit: connection to X server lost

waiting for X server to shut down debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype eow@openssh.com reply 0
debug1: channel 1: free: x11, nchannels 2
X connection to ssh:10.0 broken (explicit kill or server shutdown).
debug1: channel 0: free: client-session, nchannels 1
Connection to 172.17.0.2 closed.
Transferred: sent 91292, received 92728 bytes, in 3.1 seconds
Bytes per second: sent 29350.8, received 29812.5
debug1: Exit status 1
(II) Server terminated successfully (0). Closing log file.

deallocvt: can't open console
henriquehbr
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1 Answers1

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The "-d" option of thesshd command is used for debugging. It has this effect:

Debug mode. The server sends verbose debug output to standard error, and does not put itself in the background. The server also will not fork(2) and will only process one connection. This option is only intended for debugging for the server. Multiple -d options increase the debugging level. Maximum is 3.

Thanks to Kenster for his answer on Unix & Linux StackExchange

henriquehbr
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