I've run in to this problem as well, with these x2go versions:

Client (Mac)

• x2goclient 4.0.5.0 (OS X 10.9+ build) or 4.0.5.1 preview (December 2015 build)
• OS X 10.11.3
• XQuartz 2.7.8

Server (Linux)

• x2goagent: 3.5.0.32
• x2goserver: 4.0.1.19
• x2goserver-extensions: 4.0.1.19
• Fedora 23 (with updates as of 2016-02-17)

Steps to reproduce:

1. Run 'x2goclient --debug' and open a session
2. Observe frequent xmodmap commands while session is active
3. Quit session to see a large number of SshProcess objects freed

This came to my attention because the default SELinux/audit settings on Fedora 23 log five events for each xmodmap ssh command executed on the server by the client. That's 1800 events per hour when an x2go session is active.

Judging from ONMainWindow::slotSetModMap() in onmainwindow.cpp, it looks like the intent is to only run the xmodmap command if kbMap is empty (maybe there's an expected way for kbMap to get cleared so it has to be periodically checked?). However, slotSetModMap() runs every 10 seconds and executes a command every time. It's not clear to me how kbMap becomes empty.

Furthermore, the SshProcess objects are not cleaned up until the session is exited. The 'processes' QList in SshMasterConnection grows without bound.

Logs from x2goclient --debug:

""" x2go-DEBUG-../src/sshprocess.cpp:199> Executing remote command via SshProcess object 6: "export DISPLAY=":50"; echo "keycode 8 = a A aring Aring <snip>" x2go-DEBUG-../src/sshprocess.cpp:204> Running masterCon->addChannelConnection(this, '"d93c9f1a-2d4d-42fb-92a9-5373621768f6"', '"bash -c 'echo "X2GODATABEGIN:d93c9f1a-2d4d-42fb-92a9-5373621768f6"; export PATH="/usr/local/bin:/usr/bin:/bin"; export DISPLAY=":50"; echo "keycode 8 = a A aring Aring keycode 9 = s S ssharp Iacut"'); x2go-DEBUG-../src/sshmasterconnection.cpp:1284> Locking SSH channel connection MUTEX. x2go-DEBUG-../src/sshmasterconnection.cpp:1286> Passing new channel conenction object to channelConnections. x2go-DEBUG-../src/sshmasterconnection.cpp:1288> Unlocking SSH channel connection MUTEX. x2go-DEBUG-../src/sshmasterconnection.cpp:1476> Creating new channel.

x2go-DEBUG-../src/sshmasterconnection.cpp:1480> New channel:0x7fcb9a7af450

x2go-DEBUG-../src/sshmasterconnection.cpp:1511> Executing remote: "bash -c 'echo "X2GODATABEGIN:d93c9f1a-2d4d-42fb-92a9-5373621768f6"; export PATH="/usr/local/bin:/usr/bin:/bin"; export DISPLAY=":50"; echo "keycode 8 = a A aring Aring <snip>" x2go-DEBUG-../src/sshmasterconnection.cpp:1534> New exec channel created.

x2go-DEBUG-../src/sshmasterconnection.cpp:1638> EOF on channel 0x7fcb9a7af450; SshProcess object: 6 x2go-DEBUG-../src/sshmasterconnection.cpp:1706> EOF sent. x2go-DEBUG-../src/sshmasterconnection.cpp:1710> Channel closed. x2go-DEBUG-../src/sshprocess.cpp:517> SSH finished: raw output (stdout): "X2GODATABEGIN:d93c9f1a-2d4d-42fb-92a9-5373621768f6 X2GODATAEND:d93c9f1a-2d4d-42fb-92a9-5373621768f6 " x2go-DEBUG-../src/sshprocess.cpp:528> SSH finished: true - "" (6). <repeat every 10 seconds> """

And the log of SshProcess cleanup when the session is disconnected after a little over one minute:

""" x2go-DEBUG-../src/sshmasterconnection.cpp:715> SshMasterConnection, instance SshMasterConnection(0x7fcb9cc51a90) thread finished. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshprocess.cpp:52> SshProcess destructor called. x2go-DEBUG-../src/sshmasterconnection.cpp:722> SshMasterConnection, instance SshMasterConnection(0x7fcb9cc51a90) finished destructor. """

-- Mat Martineau Intel OTC