Hi,
I wanted to ask about the new vfs_block and how a block file can be made persistent between Goa runs. My vfs_block configuration is as follows:
<content> <rom label="vfs"/> <rom label="vfs_block"/> <rom label="vfs.lib.so"/> <rom label="vfs_import.lib.so"/> <rom label="vfs_lwext4.lib.so" /> <rom label="snapper_block.raw"/> </content>
<start name="vfs_block" ram="1G"> <provides><service name="Block"/></provides> <config> <vfs> <ram/> <import> <rom name="snapper_block.raw"/> </import> </vfs> <policy label_prefix="vfs" file="/snapper_block.raw" block_size="512" writeable="yes"/>
</config> </start>
My program runs successfully, however changes made to the block file (snapper_block.raw) do not persist. This is because I use <ram/>. But without <ram/> I get an error that the block file is inaccessible.
How can I make the block changes persist between runs? In previous versions of Genode I could achieve this with lx_block, but I am unsure how to do this with vfs_block.
Best, Rumen
Hello Rumen
On 7/10/25 17:41, Rumen Mitov wrote:
My program runs successfully, however changes made to the block file (snapper_block.raw) do not persist. This is because I use <ram/>. But without <ram/> I get an error that the block file is inaccessible.
The way you configured `vfs_block`, it imports the content of the ROM in to the RAM and allows to modify it, but the changes can't be written back.
How can I make the block changes persist between runs? In previous versions of Genode I could achieve this with lx_block, but I am unsure how to do this with vfs_block.
I would try something as follows:
```xml <requires> <file_system label="lx_block"/> </requires>
....
<start name="vfs_block" ram="1G"> <provides><service name="Block"/></provides> <config> <vfs> <fs label="lx_block"/> </vfs> <policy label_prefix="vfs" file="/snapper_block.raw" block_size="512" writeable="yes"/>
</config> </start> ```
then remove the `<rom label="snapper_block.raw"/>` from `<content>`.
This should start an `lx_fs` component in the runtime. Which if I remember correctly will serve the content of the sub directory `lx_block`. Your needs to be in that sub-directory.
I write this from the top of my head without actually trying it out, so there might be some steps I missed.
Regards, Pirmin
Hi,
Thanks for the tip! I had some trouble with routing the components, but I managed to get it to work by explicitly adding the lx_fs component. I am attaching my runtime here for future reference.
Best, Rumen ________________________________ From: Pirmin Duss via users users@lists.genode.org Sent: Friday, July 11, 2025 7:28 AM To: users@lists.genode.org users@lists.genode.org Cc: Pirmin Duss pirmin.duss@gapfruit.com Subject: Re: vfs_block Persistence
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Hello Rumen
On 7/10/25 17:41, Rumen Mitov wrote:
My program runs successfully, however changes made to the block file (snapper_block.raw) do not persist. This is because I use <ram/>. But without <ram/> I get an error that the block file is inaccessible.
The way you configured `vfs_block`, it imports the content of the ROM in to the RAM and allows to modify it, but the changes can't be written back.
How can I make the block changes persist between runs? In previous versions of Genode I could achieve this with lx_block, but I am unsure how to do this with vfs_block.
I would try something as follows:
```xml <requires> <file_system label="lx_block"/> </requires>
....
<start name="vfs_block" ram="1G"> <provides><service name="Block"/></provides> <config> <vfs> <fs label="lx_block"/> </vfs> <policy label_prefix="vfs" file="/snapper_block.raw" block_size="512" writeable="yes"/>
</config> </start> ```
then remove the `<rom label="snapper_block.raw"/>` from `<content>`.
This should start an `lx_fs` component in the runtime. Which if I remember correctly will serve the content of the sub directory `lx_block`. Your needs to be in that sub-directory.
I write this from the top of my head without actually trying it out, so there might be some steps I missed.
Regards, Pirmin
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Pirmin Duss -
Rumen Mitov