x11vnc server on ubuntu 18.04 hangs after ~ 24 hours

Question

I have 3 Dell Latitude computers on which I have installed Ubuntu. The installation was done from the same source stick, was done several days apart and I have followed home developed protocol ( a list of things to install and commands to run int he terminal).

Even though, I have followed the same protocol I have gotten different behaviour from these machines. One of the problems that bother me the most is that the X11VNC server I have installed following a recipe from main source or also repeated here, fails after ~ 24 hours. When this happens, one of the core is completely consumed by the x11vnc server.

I could access the computer via ssh and here is some information.

I don't know what is the difference between installations and configurations of these computers and why x11vnc server fails after some time. I would appreciate any followup question you might have. I will be updating the question with all new information I will find.

OS:

username:~$  lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04 LTS
Release:    18.04
Codename:   bionic

X11vnc version

29/07/2018 17:15:54 x11vnc version: 0.9.13 lastmod: 2011-08-10  pid: 3283
29/07/2018 17:15:54 XOpenDisplay("") failed.
29/07/2018 17:15:54 Trying again with XAUTHLOCALHOSTNAME=localhost ...
29/07/2018 17:15:54 
29/07/2018 17:15:54 *** XOpenDisplay failed. No -display or DISPLAY.
29/07/2018 17:15:54 *** Trying ":0" in 4 seconds.  Press Ctrl-C to abort.
29/07/2018 17:15:54 *** 1 2 3 4 
29/07/2018 17:15:58 *** XOpenDisplay of ":0" successful.
29/07/2018 17:15:58 
29/07/2018 17:15:58 Using X display :0
29/07/2018 17:15:58 rootwin: 0x191 reswin: 0x3400001 dpy: 0xc6189f90

before: sudo systemctl restart x11vnc

x11vnc.service - Start x11vnc at startup.
   Loaded: loaded (/lib/systemd/system/x11vnc.service; enabled; vendor preset: e
   Active: active (running) since Fri 2018-07-27 17:52:36 EDT; 1 day 22h ago
 Main PID: 1604 (x11vnc)
    Tasks: 2 (limit: 4915)
   CGroup: /system.slice/x11vnc.service
           ├─1604 /usr/bin/x11vnc -loop -forever -bg -rfbport 5900 -xkb -noxreco
           └─1606 /usr/bin/x11vnc -loop -forever -bg -rfbport 5900 -xkb -noxreco

Jul 28 10:10:46 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:10:46 client_count: 1
Jul 28 10:10:46 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:10:46 Client 137.187.82
Jul 28 10:10:46 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:10:46 Statistics       
Jul 28 10:10:46 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:10:46  TOTALS          
Jul 28 10:10:46 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:10:46 Statistics       
Jul 28 10:10:46 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:10:46  TOTALS          
Jul 28 10:15:47 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:15:47 idle keyboard:   
Jul 28 10:37:22 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:37:22 Got connection fr
Jul 28 10:37:22 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:37:22   other clients:
Jul 28 10:37:22 icarus-ii-50 x11vnc[1604]: 28/07/2018 10:37:22      128.231.4.12
~
~

After: sudo systemctl restart x11vnc

    x11vnc.service - Start x11vnc at startup.
   Loaded: loaded (/lib/systemd/system/x11vnc.service; enabled; vendor preset: enabled)
   Active: active (running) since Sun 2018-07-29 16:37:40 EDT; 28min ago
 Main PID: 30404 (x11vnc)
    Tasks: 2 (limit: 4915)
   CGroup: /system.slice/x11vnc.service
           ├─30404 /usr/bin/x11vnc -loop -forever -bg -rfbport 5900 -xkb -noxrecord -noxfixe
           └─30405 /usr/bin/x11vnc -loop -forever -bg -rfbport 5900 -xkb -noxrecord -noxfixe

Jul 29 17:03:35 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:35 Enabling full-color cursor u
Jul 29 17:03:35 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:35 Enabling NewFBSize protocol 
Jul 29 17:03:35 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:35 Switching from ZRLE to hexti
Jul 29 17:03:36 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:36 rfbProcessClientNormalMessag
Jul 29 17:03:36 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:36 rfbProcessClientNormalMessag
Jul 29 17:03:36 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:36 rfbProcessClientNormalMessag
Jul 29 17:03:36 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:36 rfbProcessClientNormalMessag
Jul 29 17:03:36 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:36 Enabling full-color cursor u
Jul 29 17:03:36 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:36 Enabling NewFBSize protocol 
Jul 29 17:03:36 icarus-ii-50 x11vnc[30404]: 29/07/2018 17:03:36 Switching from hextile to ZR
lines 1-19/19 (END)

here is the record of 100% CPU consumption by VNC server

top - 18:53:15 up 2 days,  1:01,  2 users,  load average: 1.39, 1.45, 1.41
Tasks: 261 total,   2 running, 192 sleeping,   0 stopped,   1 zombie
%Cpu(s):  3.0 us, 10.3 sy,  0.0 ni, 86.7 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  8031704 total,  2470912 free,  4375192 used,  1185600 buff/cache
KiB Swap:  2097148 total,  2097148 free,        0 used.  3068456 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                                                 
30405 root      20   0  154924  34324  22212 R 100.0  0.4  48:41.74 x11vnc    

Answer 1

I believe I have solved this problem by installing the newest version of x11vnc which is 0.9.15.

The new version has some bugs fixed and memory leaks. It is conceivable that memory leak is the problem with the older version and that is why it would hang after a few hours.

Please see the protocol here as an answer to another question