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Embedded Elixir (without Nerves)

Lasse Skindstad Ebert on October 20, 2019

This story was originally posted by me on Medium on 2018-08-29, but moved here since I'm closing my Medium account. I love Nerves. Unfortunately I...
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Paulo Renato • • Edited

This is because most of the file system is read-only, because the gateway should not be able to get to a state where it can’t just reboot and everything is fine again.

Sounds like that the use of an almost read-only file system will also improve its security.

So only the /data dir is writable?

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Lasse Skindstad Ebert • • Edited

IMHO the greatest advantage of the write-only read-only filesystem on an embedded device is that a restart of the device is more likely to fix a bad state and make the device boot successfully.

Yes, on my specific device, the /data dir was already mounted as read-write.

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Paulo Renato •

I think you meant read-only instead write-only in your reply?

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Lasse Skindstad Ebert •

I did 👍

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Paulo Renato •

HOME: Again, not specific to Erlang, but Erlang tries to save a cookie file in the home dir for some reason.

The reason for this cookie existence is to allow to run distributed Erlang/Elixir. So the cookie will be used to allow nodes to talk with each other.

You can read more here, where at some point you will read:

First of all, you need to ensure all machines have a ~/.erlang.cookie file with exactly the same value.

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Lasse Skindstad Ebert •

Correct :)

You can also set the cookie on startup of the application with some command line argument or env var, which might prevent erlang from saving a generated cookie. I haven't tried this though.