fix "shmget: No space left on device"

[andrew-ld]

Types of changes

Put an x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Purpose of changes

fix #423

[budtmo]

Hi @andrew-ld ,

thank you for the PR. if I understand correctly, using shm will accelerates the screen reading. I never have issue with the shm on. have you found the root cause on your host machine why it need to be off? because I am not sure if it is a good idea to make it off by default and it might have side affects (mess up with colour etc). instead of making it off by default, I think we can pass additional flag for that through environment variable. what do you think?

[andrew-ld]

@budtmo hi, i found the root cause but being on a kubernetes cluster with hundreds of other programs and to solve this problem i would have to change a sysctl that would apply to the whole machine/cluster i decided to find an alternative solution.

Reading the documentation of x11vnc, it seems that the side effects with the use of noshm do not apply to this program/use case.

anyway in any case to resolve any doubts I added an environment variable.