Increase inotify watchers in Docker images during build

docker-increase-inotify-max-user-watches.md

Increasing fs.inotify.max_user_watches for Docker images

TL;DR You can't set those for an image during build time becasue Docker takes the sysctl configuration from the Host. So, set the config on your host machine.

As in this link, to increase the maximum watchers, we need set fs.inotify.max_user_watches to a higher number in /etc/sysctl.conf.

$ echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf
$ sudo sysctl -p

So, I immediately tried to add it to Dockerfile and build the image only to see the following error:

sysctl: setting key "fs.inotify.max_user_watches": Read-only file system

After some research, I realised that Docker doesn't let the sysctl to be modified during build for images because it takes it from the host.

So, I had to set the sysctl on the host, not in the `Dockerfile.

Thanks. It worked