Use the below procedure to make CloudView NMS server work on DigitalOcean "droplet"
with 512MB RAM ($5.00 a month Ubuntu VPS). Ideally CloudView NMS requires at least 2GB
of RAM; however it will still work OK if you configure Linux swap file per below 
instructions. Use "linuxquckstartnogui.txt" instructions (found on our download web 
page) to install CloudView NMS Server on the "droplet". Now, if you run 
"sudo ./startservice.sh" WITHOUT the below procedure, you may experience the following:

     a. startservice.sh  script fails because of "not enough memory".
     b. The CloudView NMS server "java" process reports to be "killed" when you start
        adding devices to the maps.

So let us configure the swap file.

1. Turn any swap file off.

     sudo swapoff -a

2. Check that no swap file is used:

     sudo swapon -s

   The above must return nothing (or empty list) meaning that no swap file is used.

3. Check the file system:

     df

   The output is:
Filesystem     1K-blocks    Used Available Use% Mounted on
udev              242164       0    242164   0% /dev
tmpfs              50020    2860     47160   6% /run
/dev/vda1       20510568 2656208  16798488  14% /
tmpfs             250100       0    250100   0% /dev/shm
tmpfs               5120       0      5120   0% /run/lock
tmpfs             250100       0    250100   0% /sys/fs/cgroup
tmpfs              50020       0     50020   0% /run/user/0

4. So per above "df" output we are using just 14% of /dev/vda1. Let us create 4GB 
   swap file with the full path "/swapfile".

  sudo dd if=/dev/zero of=/swapfile bs=1024 count=4096k

The output is:
4194304+0 records in
4194304+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 17.6636 s, 243 MB/s

  Let us check the file:

   ls -l /swapfile

-rw------- 1 root root 4294967296 Dec 21 22:44 /swapfile

4. Subsequently we are going to prepare the swap file by creating a linux swap area:

   sudo mkswap /swapfile

  The output is:
Setting up swapspace version 1, size = 4 GiB (4294963200 bytes)
no label, UUID=9b8753ce-a535-429f-af5a-9515b05964f6

5. Finish up by activating the swap file:

  sudo swapon /swapfile

6. Now let us just to check that everything is OK:

  swapon -s

 The output is:
Filename                                Type            Size    Used    Priority
/swapfile                               file            4194300 0       -1

7. After all the above you are ready to run ./startservice.sh  again. It should be OK now.