Running the filesystem readonly

[WSchweizer]

I’m working on a solution to run the whole filesystem in readonly mode with overlay to tmpfs.
The intention is to use this on embeded systems to make them robust against power loss and to reduce the wear out of micro ssd cards.

On my development desktop system I do this by mounting the root directory / with overlay-fs
with lower on readonly mounted root partition and upper and work on a tmpfs.

All this is implemented by a script as dracut-pre-pivot hook and seems to work correctly.

But I recognised two things:

1. after booting Tumbleweed in my readonly-fs-mode the command “zypper ps -s” shows many processes using deleted files
   with Leap 15.0 no processes with deleted files are reported.

2. After recent updates of Tumbleweed (since two or three weeks) I get lots of messages on the console:
   systemd-journald[556]: Failed to open system journal: Operation not supported

Can you help me locate and eliminate this issues?
Thank you.

[nrickert]

@WSchweizer

I’m working on a solution to run the whole filesystem in readonly mode with overlay to tmpfs.

That’s pretty much how the live DVD systems work, except that they use “squashfs” (compressed file system) for the underlying readonly part. I suggest you look into how those are setup.

[knurpht]

@nrickert

That’s pretty much how the live DVD systems work, except that they use “squashfs” (compressed file system) for the underlying readonly part. I suggest you look into how those are setup.

The ‘Live’ images do use overlayfs. I use, instead of taking my laptop everywhere, a USB3 external SSD with an openSUSE Leap ( works for TW as well ) image. After dd’ing the live image and booting from it it extends the fs to an overlayfs allowing me to update and extend it. Maybe that is what you’re looking for.

[tsu2]

If you install the “Transactional Server” role,
You’ll be installing your system with a root read only.

See the release notes about running on a read only root,
Instead of normal commands to install, update and otherwise modify your root file system, you use special “transactional” commands to queue your desired changes, which are applied on reboot.

In this configuration, the system itself should know how to do things like maintain its journal.

TSU

[WSchweizer]

@tsu2

If you install the “Transactional Server” role,
You’ll be installing your system with a root read only.

See the release notes about running on a read only root,
Instead of normal commands to install, update and otherwise modify your root file system, you use special “transactional” commands to queue your desired changes, which are applied on reboot.

In this configuration, the system itself should know how to do things like maintain its journal.

TSU

Yes I know that and I am using it on server systems.
But on embeded systems the whole external storage has to be readonly, not only root.
I like to have all writing to the tmpfs in ram.