qemu: mount rootfs as read-only #60
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The contract is that the rootfs is mounted read-only.
This was not happening.
When running the tool as an unprivileged user, this essentially was a no-op,
but when running it using a rootfs owned by the user, it was then possible
to write to those directories:
```
ls /tmp/main-s390x-chantra/home; \
> vmtest -k s390x/kbuild-output/arch/s390/boot/bzImage -a s390x -r /tmp/main-s390x-chantra "touch /home/a"; \
> cargo run -- -k s390x/kbuild-output/arch/s390/boot/bzImage -a s390x -r /tmp/main-s390x-chantra "touch /home/b"; \
> ls /tmp/main-s390x-chantra/home
=> bzImage
===> Booting
===> Setting up VM
===> Running command
Finished dev [unoptimized + debuginfo] target(s) in 0.04s
Running `target/debug/vmtest -k s390x/kbuild-output/arch/s390/boot/bzImage -a s390x -r /tmp/main-s390x-chantra 'touch /home/b'`
=> bzImage
===> Booting
===> Setting up VM
===> Running command
touch: cannot touch '/home/b': Read-only file system
Command failed with exit code: 1
a
```
Signed-off-by: Manu Bretelle <[email protected]>
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In c1620eb I changed rootfs to rw cuz I think a lot of tools were breaking. Is there an inconsistency in the doc I missed somewhere? |
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On Fri, Jan 26, 2024 at 8:32 AM Daniel Xu ***@***.***> wrote:
In c1620eb
<c1620eb>
I changed rootfs to rw cuz I think a lot of tools were breaking. Is there
an inconsistency in the doc I missed somewhere?
Oh, the architecture.md doc may need update then
“””
The second big idea is that we use 9p filesystems to share host filesystem
inside the guest. This is useful so that vmtest targets can import/export
data in bulk without having to specify what to copy. In a kernel target,
vmtest exports two volumes: `/mnt/vmtest` and the root filesystem. The
latter export effectively gives the guest VM the same userspace environment
as the host, except we mount it read-only so the guest cannot do too much
damage to the host.
“””
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Ah ok. If you are ok with current behavior I will put it on my todo list to update the diagram then. And probably upload source for diagram |
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On Fri, Jan 26, 2024 at 8:48 AM Daniel Xu ***@***.***> wrote:
Ah ok. If you are ok with current behavior I will put it on my todo list
to update the diagram then. And probably upload source for diagram
yeah. I am fine with the current behaviour as it is non destructive by
default for the rootfs when ran unprivileged.
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ok, closing this then as it is just a matter of updating the doc |
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The contract is that the rootfs is mounted read-only. This was not happening.
When running the tool as an unprivileged user, this essentially was a no-op, but when running it using a rootfs owned by the user, it was then possible to write to those directories: