X2Go Bug report logs - #1382
X2Go Agent terminates unexpectedly only for LDAP users

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Message #5 received at submit@bugs.x2go.org (full text, mbox, reply):

From: Fred Chen <fred@lionsemi.com>

To: submit@bugs.x2go.org

Subject: X2Go Agent terminates unexpectedly only for LDAP users

Date: Tue, 9 Apr 2019 23:55:50 -0700

[Message part 1 (text/plain, inline)]

Package: x2goagent
Version: 4.1.0.3-1

=====================

It's not clear if this is an issue with x2goagent, x2goserver or perhaps
some server configuration problem.

* We ran into this problem on CentOS 7.6 (kernel 3.10.0-957.10.1) where we
could not remotely connect to the server using X2GO and the only error
message of note was: "Failed to start X2Go Agent session with ID
fred-<Session #>_stDMATE_dp32. X2Go Agent terminated unexpectedly. Aborting
session startup." (Longer output of /var/log/messages below)

* This problem only seems to be present for users authenticated via LDAP
(via sssd/pam). When I created a dummy local user (with identical login
shell setup), I was able to launch an X2GO session as that user with no
problem (using the same client).

* The LDAP user can SSH into the server and can also launch a remote
desktop session with xrdp using a Royal TS client. That remote desktop
session exercises most of the same services required by X2GO such as
systemd-logind, which helps rule out those services.

* It also appears that when starting the X2GO session that the LDAP user
authenticates successfully to initiate the creation of a session so I don't
believe it is an authentication issue.  It almost seems as if some user
credentials (uid or uidNumber) get lost or dropped when passed to
nx-libs/x2goagent that prevent creation of the display port and ultimately
terminates the session.

Apr  9 23:39:47 lioncub7 systemd-logind: Removed session 2.
Apr  9 23:39:47 lioncub7 systemd: Removed slice User Slice of fred.
Apr  9 23:39:48 lioncub7 systemd: Created slice User Slice of fred.
Apr  9 23:39:48 lioncub7 systemd-logind: New session 10 of user fred.
Apr  9 23:39:48 lioncub7 systemd: Started Session 10 of user fred.
Apr  9 23:39:50 lioncub7 /usr/bin/x2gostartagent: x2gostartagent called
with options: 1920x1170 wan 16m-jpeg-9 unix-kde-depth_32 us auto 1 D MATE
both
Apr  9 23:39:50 lioncub7 /usr/bin/x2gosessionlimit[16405]: x2gosessionlimit
has been called
Apr  9 23:39:51 lioncub7 x2golistsessions: x2golistsessions has been called
with options: --all-servers
Apr  9 23:39:51 lioncub7 x2gocleansessions:
fred-50-1554878391_stDMATE_dp32: state file for this session does not
exist: /tmp/.x2go-fred/C-fred-50-1554878391_stDMATE_dp32/state (this can be
ignored during session startups)
Apr  9 23:39:52 lioncub7 /usr/bin/x2gofeature: x2gofeature called with
options: X2GO_RUN_EXTENSIONS
Apr  9 23:39:52 lioncub7
/usr/share/x2go/x2gofeature.d/x2goserver-extensions.features:
x2goserver-extensions.features called with options: X2GO_RUN_EXTENSIONS
Apr  9 23:39:52 lioncub7 /usr/bin/x2goserver-run-extensions:
x2goserver-run-extensions called with options:
fred-50-1554878391_stDMATE_dp32 pre-start
Apr  9 23:39:52 lioncub7 /usr/bin/x2gostartagent: creating new session:
fred-50-1554878391_stDMATE_dp32 3bb04b5de35c14108c76e0b7bd59214f 16535
*<Internal
IP>* 39539 39540 39541 -1 -1
Apr  9 23:39:52 lioncub7 /usr/bin/x2gostartagent: Failed to start X2Go
Agent session with ID fred-50-1554878391_stDMATE_dp32. X2Go Agent
terminated unexpectedly. Aborting session startup.
Apr  9 23:39:52 lioncub7 /usr/bin/x2gofeature: x2gofeature called with
options: X2GO_RUN_EXTENSIONS
Apr  9 23:39:52 lioncub7
/usr/share/x2go/x2gofeature.d/x2goserver-extensions.features:
x2goserver-extensions.features called with options: X2GO_RUN_EXTENSIONS
Apr  9 23:39:52 lioncub7 /usr/bin/x2goserver-run-extensions:
x2goserver-run-extensions called with options:
fred-50-1554878391_stDMATE_dp32 fail-start
Apr  9 23:40:01 lioncub7 systemd: Started Session 11 of user root.
Apr  9 23:40:23 lioncub7 su: (to fred) root on none
Apr  9 23:40:23 lioncub7 systemd: Started Session c6 of user fred.
Apr  9 23:40:23 lioncub7 su: (to fred) root on none
Apr  9 23:40:23 lioncub7 systemd: Started Session c7 of user fred.
Apr  9 23:40:23 lioncub7 x2goumount-session: x2goumount-session has been
called with options: fred-50-1554878391_stDMATE_dp32

[Message part 2 (text/html, inline)]

Message #10 received at 1382@bugs.x2go.org (full text, mbox, reply):

From: Fred Chen <fred@lionsemi.com>

To: 1382@bugs.x2go.org

Subject: Issue resolved

Date: Wed, 17 Apr 2019 01:44:29 -0700

It turns out the source of the problem was a single line in the LDAP user’s .bashrc that was not in the local user’s config.

I originally did not even look at this because both the local user and the LDAP user were configured with /bin/csh as their login shell but it seems that the .bashrc is still read by the desktop manager or some other service as part of the Xsession.

We were using environment modules and the offending line was calling “module load” on a module that then loaded other modules.

When a new bash shell is started from the user’s session, there doesn’t seem to be a problem so I’m not sure why this terminates the session but it’s mostly a non-issue now for us.

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