Extending read-only state to /sysroot and /boot #1265

cgwalters · 2017-10-12T13:37:48Z

Today ostree has a ro bind mount over /usr, but one can just do e.g. rm -rf /sysroot/* and the whole system is destroyed.

Similarly, we tried to have support for /boot as a ro mount but it needs work.

What we should do is have these be ro by default, and then have apps using libostree create a new mount namespace, and make manipulations there. That way the system stays read-only to everything else. Alternatively, we could teach libostree how to do that internally, but it'd get ugly fast...we'd need to fork off a subprocess basically.

For example rpm-ostreed and eos-updater could change their systemd unit files to create a new mount namespace, and tell libostree that one is set up.

(Conceptually this overlaps a ton with systemd's ProtectSystem=strict...we're basically imposing that on the whole system by default)

The text was updated successfully, but these errors were encountered:

cgwalters · 2017-12-23T09:26:05Z

See also for /tmp:
https://pagure.io/fedora-atomic/pull-request/62
coreos/rpm-ostree#820

giuseppe · 2017-12-23T10:29:44Z

would this be an issue for system containers that use /ostree/deploy/$OS_NAME/$DEST_FILE for creating hard links?

cgwalters · 2017-12-27T14:04:14Z

@giuseppe an important bit from the above is:

...and then have apps using libostree create a new mount namespace, and make manipulations there.

The goal here isn't to make things truly immutable, it's to prevent things like restorecon -R / from destroying the system. And similar non-ostree-aware tools.

See also on-list discussion:

https://mail.gnome.org/archives/ostree-list/2017-December/msg00009.html

giuseppe · 2017-12-27T20:25:51Z

I see, thanks. Could the new API allow also the current mount namespace to be used? It will be the user responsibility to ensure a new mount namespace is created and /sysroot can be remounted as writeable (and back to ro if needed).

cgwalters · 2018-10-29T19:01:20Z

PR in #1767

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`, which we can't mount readonly as we want `/etc` to be writable (and `/var` if it's there too). So we actually make it into a bind mount. Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

Part of the implementation of ostreedev/ostree#1265 Convert to systemd mount units so we can easily specify the `ro` flag, and also to use the `LABEL={root,var}` rather than UUIDs. Enable the sysroot/readonly flag.

Prep for ostreedev/ostree#1265

cgwalters · 2018-12-26T18:47:04Z

Requirements to implement this for Fedora CoreOS:

coreos/fedora-coreos-config#39
coreos/ignition-dracut#36

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`, which we can't mount readonly as we want `/etc` to be writable (and `/var` if it's there too). So we actually make it into a bind mount. Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

Prep for ostreedev/ostree#1265

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`, which we can't mount readonly as we want `/etc` to be writable (and `/var` if it's there too). So we actually make it into a bind mount. Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

jlebon · 2019-04-18T15:17:19Z

Yeah, we really should fix this. Right now, restorecon -R / and autorelabel=1 are super dangerous (see e.g. user report at https://twitter.com/goozbach/status/1118697493657681920?s=19).

To anyone in that situation, you can recover from this by booting with enforcing=0, then:

# rpm-ostree status -v # copy "BaseCommit" or if missing, "Commit"
# ostree checkout -H $checksum /ostree/repo/tmp/selinux-fix
# ostree fsck --delete
# ostree commit --consume --link-checkout-speedup --orphan --selinux-policy=/ /ostree/repo/tmp/selinux-fix
# restorecon -Rv /var
# restorecon -Rv /etc
# ostree admin deploy fedora-atomic:fedora/29/x86_64/atomic-host # or whatever refspec you're on
# reboot

At this point, you should be able to boot in enforcing mode again. Final cleanup:

# rpm-ostree cleanup --rollback

Note this will blow away all your layered packages; you'll have to relayer those again.

goozbach · 2019-04-18T18:27:27Z

should that be BaseCommit or Commit instead of checksum?

jlebon · 2019-04-18T18:33:50Z

Thanks! I edited the original comment.

goozbach · 2019-04-19T04:31:22Z

For future reference I had to do an rpm-ostree upgrade prior to the above steps for them to work.

Other than that, this workaround is good!

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`, which we can't mount readonly as we want `/etc` to be writable (and `/var` if it's there too). So we actually make it into a bind mount. Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`; so we make `/etc` a writable bind mount in this case. We also need to handle `/var` in the "OSTree default" case of a bind mount; the systemd generator now looks at the writability state of `/sysroot` and uses that to determine whether it should have the `var.mount` unit happen before or after `ostree-remount.service.` Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

Prep for using the default mount namespace handling there that will land as part of the read-only `/sysroot` and `/boot` work. See ostreedev#1265

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`; so we make `/etc` a writable bind mount in this case. We also need to handle `/var` in the "OSTree default" case of a bind mount; the systemd generator now looks at the writability state of `/sysroot` and uses that to determine whether it should have the `var.mount` unit happen before or after `ostree-remount.service.` Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

Prep for using the default mount namespace handling there that will land as part of the read-only `/sysroot` and `/boot` work. See ostreedev#1265

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`; so we make `/etc` a writable bind mount in this case. We also need to handle `/var` in the "OSTree default" case of a bind mount; the systemd generator now looks at the writability state of `/sysroot` and uses that to determine whether it should have the `var.mount` unit happen before or after `ostree-remount.service.` Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

Let's opt-in to this by default. See ostreedev/ostree#1265 This currently is a no-op if the required ostree support hasn't landed yet, so I think we can safely merge this PR first.

We want to support extending the read-only state to cover `/sysroot` and `/boot`, since conceptually all of the data there should only be written via libostree. Or at least for `/boot` should *mostly* just be written by ostree. This change needs to be opt-in though to avoid breaking anyone. Add a `sysroot/readonly` key to the repository config which instructs `ostree-remount.service` to ensure `/sysroot` is read-only. This requires a bit of a dance because `/sysroot` is actually the same filesystem as `/`; so we make `/etc` a writable bind mount in this case. We also need to handle `/var` in the "OSTree default" case of a bind mount; the systemd generator now looks at the writability state of `/sysroot` and uses that to determine whether it should have the `var.mount` unit happen before or after `ostree-remount.service.` Also add an API to instruct the libostree shared library that the caller has created a new mount namespace. This way we can freely remount read-write. This approach extends upon in a much better way previous work we did to support remounting `/boot` read-write. Closes: ostreedev#1265

Prep for using the default mount namespace handling there that will land as part of the read-only `/sysroot` and `/boot` work. See ostreedev#1265

Let's opt-in to this by default. See ostreedev/ostree#1265 This currently is a no-op if the required ostree support hasn't landed yet, so I think we can safely merge this PR first.

This is all we need to tell libostree that we support a read-only `/sysroot` and `/boot`. See ostreedev/ostree#1265 PR in ostreedev/ostree#1767

Let's opt-in to this by default. See ostreedev/ostree#1265 This currently is a no-op if the required ostree support hasn't landed yet, so I think we can safely merge this PR first.

This is all we need to tell libostree that we support a read-only `/sysroot` and `/boot`. See ostreedev/ostree#1265 PR in ostreedev/ostree#1767

We want to use the new read-only `/sysroot` feature of libostree. Opt-in to that to tell cosa we support it and want it. For more details, see: ostreedev/ostree#1265 coreos/coreos-assembler#1235

bam80 · 2020-04-21T10:24:33Z

Yeah, we really should fix this. Right now, restorecon -R / and autorelabel=1 are super dangerous

I still broke my Fedora Silverblue 31 system with restorecon -R / command. Isn't it fixed yet?

jlebon · 2020-04-21T13:35:32Z

I still broke my Fedora Silverblue 31 system with restorecon -R / command. Isn't it fixed yet?

OSTree knows how to handle read-only /sysroot, but it doesn't automatically apply to existing nodes, because it requires modifying files not maintained by updates. We'll probably need a systemd service in fedora-release-silverblue or something to transition over existing systems.

bam80 · 2020-04-21T14:38:18Z

Thanks @jlebon. Could we dedicate a separate issue for that part of the task then?

We want to use the new read-only `/sysroot` feature of libostree. Opt-in to that to tell cosa we support it and want it. For more details, see: ostreedev/ostree#1265 coreos/coreos-assembler#1235

cgwalters mentioned this issue Oct 12, 2017

syscontainers: Fall back to destination projectatomic/atomic#1114

Closed

cgwalters added the enhancement label Oct 12, 2017

This was referenced Jan 4, 2018

Admin command somtimes becomes useless when more than two deployments exist #1394

Open

sysroot: Support /boot on / for syslinux and uboot #1404

Closed

cgwalters mentioned this issue Jan 16, 2018

ostree admin deploy: Add --no-prune option #1418

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1 task

cgwalters mentioned this issue Oct 29, 2018

Support mounting /sysroot (and /boot) read-only #1767

Merged

cgwalters mentioned this issue Dec 26, 2018

WIP: image: Enable read-only /boot and /sysroot coreos/fedora-coreos-config#39

Closed

cgwalters added a commit to cgwalters/ignition-dracut that referenced this issue Dec 26, 2018

ignition-firstboot-complete.service: Remount /boot rw

a3922f9

Prep for ostreedev/ostree#1265

cgwalters mentioned this issue Dec 26, 2018

ignition-firstboot-complete.service: Remount /boot rw coreos/ignition-dracut#36

Merged

cgwalters added a commit to cgwalters/ignition-dracut that referenced this issue Jan 3, 2019

ignition-firstboot-complete.service: Remount /boot rw

650d58c

Prep for ostreedev/ostree#1265

cgwalters mentioned this issue Sep 5, 2019

create_disk: Enable read-only /sysroot coreos/coreos-assembler#736

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openshift-merge-robot closed this as completed in 5af403b Dec 11, 2019

jlebon mentioned this issue Mar 16, 2020

image.yaml: enable sysroot-ro coreos/fedora-coreos-config#304

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bam80 mentioned this issue Apr 20, 2020

Add initial troubleshooting guide fedora-silverblue/silverblue-docs#30

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travier mentioned this issue Jan 21, 2022

Make Silverblue more robust against SELinux labels change breakage fedora-silverblue/issue-tracker#232

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Extending read-only state to /sysroot and /boot #1265

Extending read-only state to /sysroot and /boot #1265

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Extending read-only state to /sysroot and /boot #1265

Extending read-only state to /sysroot and /boot #1265

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