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Comment by pjf | Hacker News Reader

See summary at https://kernelnewbies.org/Linux_4.19

From the page:

> Add EROFS (Enhanced Read-Only File System), a lightweight read-only file system with modern designs for scenarios which need high-performance read-only requirements, eg. firmwares in mobile phone or LIVECDs

and

> It is a experimental project, under the staging directory, and still expects to make changes to the on-disk layout.

I see it's included in the 4.19 branch of the Raspberry Pi fork of the kernel as well.

https://github.com/raspberrypi/linux/tree/rpi-4.19.y/drivers...

There is no public, open source mkfs utility/integration for it yet far as I can tell, but it seems from the original public announcement of EROFS on LKML that it will be released eventually.

> the open source of erofs-mkfs is _still_ in progress, it will be released as soon as the internal process ends.

https://lkml.org/lkml/2018/5/31/306

That's really nice. I remember having to use Read-Only on a few Raspberry Pi projects because they have a tendency to corrupt SD cards. Getting a free storage performance boost would really improve usability for my past use cases.

I recommend only writing when it is necessary, so e.g. you might want to log to /dev/null or tmpfs (I chose the latter but it adds up in RAM). Also, disable swap if at all feasible.

On top of that I recommend industrial grade SD cards using (a)MLC. They might be a bit more expensive but it is worth the stability.

I learned this from these posts (among others in the same thread 'Raspberry Pi microSD card performance comparison') [1] [2]

[1] https://news.ycombinator.com/item?id=16776344

[2] https://news.ycombinator.com/item?id=16777238

Thanks for the links, they were good reads.

Coincidentally, for those projects I did end up mounting to a tmpfs, syncing configs from a server, and writing them to a SPI flash chip with FEC. Fun to know that others suggest the same!

I was just thinking along the lines of performance improvement for the absolute garbage SD card speeds. I just remember how flipping long it would take to load a program off those things.

Linux Kernel Newbies is certainly a great resource.

The more interesting component this cycle is the fact that the release notes were written by Greg KH--worth the read in my opinion.

> The more interesting component this cycle is the fact that the release notes were written by Greg KH

That is because Greg handled this release cycle to let Linus take time off. Linus will be back for 4.20.

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