***Please visit the new simplified installation of the Raspberry Pi VNC Mirror***
This is an extension from this post: Raspberry Pi – VNC Mirror (Repeater) – Make any computer public anywhere
Having a RPi as VNC Mirror in production is a nice idea. But from time to time energy shortages make the Raspberry Pi shutdown unexpectedly where it may come to SD card corruption while a read or write process was in progress.
Another thing I experienced is that sometimes the computer you want to mirror loses the network connection or is by itself down for any reason. After this the VNCViewer will hang in a state where it wants the user to click-OK the a message and does not do anything, also if the computer which is to be mirrored comes up again in the meanwhile.
I have found out if the process is running correctly and mirroring the other computer, its Signal Ignore state is 0000000000000004.
First I get the process ID of my ssvncviewer
pidof ssvncviewer
knowing the process ID (in my case 2134), the status of the process can now be viewed
pi@rpi1 ~ $ cat /proc/2134/status Name: ssvncviewer State: S (sleeping) Tgid: 2134 Pid: 2134 PPid: 1944 TracerPid: 0 Uid: 1000 1000 1000 1000 Gid: 1000 1000 1000 1000 FDSize: 256 Groups: 4 20 24 27 29 44 46 60 100 106 999 1000 VmPeak: 16044 kB VmSize: 16044 kB VmLck: 0 kB VmPin: 0 kB VmHWM: 8904 kB VmRSS: 8904 kB VmData: 10792 kB VmStk: 136 kB VmExe: 276 kB VmLib: 3972 kB VmPTE: 18 kB VmSwap: 0 kB Threads: 1 SigQ: 0/3506 SigPnd: 0000000000000000 ShdPnd: 0000000000000000 SigBlk: 0000000000000000 SigIgn: 0000000000000004 SigCgt: 0000000000004003 CapInh: 0000000000000000 CapPrm: 0000000000000000 CapEff: 0000000000000000 CapBnd: ffffffffffffffff Cpus_allowed: 1 Cpus_allowed_list: 0 voluntary_ctxt_switches: 2071 nonvoluntary_ctxt_switches: 17019
I also tested it while the message “could not connect to …” was present.
In this case the SigIgn had the status 0000000000000006. So all we need to do is to check if SigIgn has the State of 0000000000000004. Otherwise we will simply kill the process. The scripts starts the VNCViewer again in some seconds.
This is the updated script, which is found in /home/pi/.config/autostart/vncview.sh
# Process check script: The script simply checks if a process is running and if it is not found to be running it will execute it.
# The script loops in preset intervals, hence it is possible to monitor a process continuously.
# Variables
Running=1
SleepInterval=20
ProcessInstances=`sudo ps aux | grep [s]svncviewer | wc -l`
#VNC Variables
vnc=ssvncviewer
host=vm1.sysstem.at
display=0
resolution=1920x1080
passfile=/home/pi/.vnc/passwd2
para="-display :$display -viewonly -fullscreen -shared -passwd $passfile -scale $resolution -encoding zrle"
function checkstatus() {
vncpid=$(pidof ssvncviewer)
sigign=$(sudo cat /proc/${vncpid}/status | grep SigIgn | awk '{print $2}')
}
# Logic
while [ $Running -gt 0 ]
do
if [ `sudo ps aux | grep [s]svncviewer | wc -l` -gt 0 ]; then
echo Process already running! Checking the Status.
checkstatus
if [ $sigign != "0000000000000004" ]; then
echo SSVNCViewer has not status 4
echo Killing SSVNCViewer
kill ${vncpid}
else
echo SSVNCViewer status seems to be ok
fi
else
echo Process not running! Starting process
# This is the command that should start the process in question
$vnc $host $para &
fi
# How often shall we repeat the check?
echo Sleeping for $SleepInterval seconds
sleep $SleepInterval
done
exit 0
To avoid SD card corruptions just follow the article by micerinos in the Raspberry Pi forum.
I created a script which does all the stuff (except for the apache thing) mentioned in the article, because I am lazy.
sudo bash
echo "RAMTMP=yes">>/etc/default/rcS
echo "proc /proc proc defaults 0 0">/etc/fstab
echo "tmpfs /var/log tmpfs nodev,nosuid,size=30M,mode=1777 0 0">>/etc/fstab
echo "tmpfs /tmp tmpfs nodev,nosuid,size=30M,mode=1777 0 0">>/etc/fstab
echo "/dev/mmcblk0p1 /boot vfat defaults,ro,noatime,errors=remount-ro 0 1">>/etc/fstab
echo "/dev/mmcblk0p2 / ext4 defaults,noatime 0 1">>/etc/fstab
sed -i 's/[ ! -f /etc/adjtime ]/[ ! -L /etc/adjtime ]/;' /etc/init.d/hwclock.sh
echo "BLKID_FILE="/var/local/blkid.tab"">>/etc/environment
rm /etc/mtab
ln -s /proc/self/mounts /etc/mtab
echo "DPkg {">>/etc/apt/apt.conf
echo " // Auto re-mounting of a readonly /">>/etc/apt/apt.conf
echo " Pre-Invoke { "mount -o remount,rw /"; };">>/etc/apt/apt.conf
echo " Post-Invoke { "test ${NO_APT_REMOUNT:-no} = yes || mount -o remount,ro / || true"; };">>/etc/apt/apt.conf
echo "};">>/etc/apt/apt.conf
Hope you’re lazy too! 😉
