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Virtualization: How do I share a cloud drive mounted inside the guest with the host? (lemmy.ml)

submitted 3 weeks ago* (last edited 3 weeks ago) by [email protected] to c/[email protected]

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Hi everyone! I want to be able to access a folder inside the guest that corresponds to a cloud drive that is mounted inside the guest for security purposes. I have tried setting up a shared filesystem inside Virt-Manager (KVM) with virtiofs (following this tutorial: https://absprog.com/post/qemu-kvm-shared-folder) but as soon as I mount the folder in order for it to be accessible on the ~~guest~~ host the cloud drive gets unmounted. I guess a folder cannot have two mounts at the same time. Aliasing the folder using bind and then sharing the aliased folder with the host doesn't work either. The aliased folder is simply empty on the host.

Does anyone have an idea regarding how I might accomplish this? Is KVM the right choice or would something like docker or podman better suited for this job? Thank you.

Edit: To clarify: The cloud drive is mounted inside a virtual machine for security purposes as the binary is proprietary and I do not want to mount it on the host (bwrap and the like introduce a whole lot of problems, the drive doesn't sync anymore and I have to relogin each time). I do not use the virtual machine per se, I just start it and leave it be.

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[–] [email protected] 4 points 3 weeks ago (1 children)

fwiw: if you go w the container strategy with docker or podman, you should be able to use the storage overlay based on how i'm reading your question.

it's hard to ascertain any path forward w/o knowing more details on the cloud drive and how's it's currently mounted on the guest instance.

[–] [email protected] 1 points 3 weeks ago (1 children)

I have no idea how it is mounted (how can I find out?) because the binary is proprietary. This is why it is contained inside a virtual machine.

[–] [email protected] 3 points 3 weeks ago (1 children)

run the command mount with sudo access and if you can see it enumerated in the printout then you should be able to proceed with either a container overlay or separate mount point.

if not, then it'll get very advanced very quickly; do you know how to use strace?

[–] [email protected] 2 points 3 weeks ago (1 children)

I just checked and it is mounted as a fuse drive.

do you know how to use strace?

A very confident NO :)

[–] [email protected] 4 points 3 weeks ago* (last edited 3 weeks ago) (1 children)

fortunately we won't have to bother w strace; but i think i can see where you'll be blocked.

do you have to provide a username/password or token when you try to access the drive now?

if yes, then you should be able to mount it like you're trying to do using instructions like these and you can use the information from the last printout to fill in the blanks.

if no, then its access is controlled outside of your guest instance and you'll need to ask your admins to enable access.

[–] [email protected] 1 points 3 weeks ago (1 children)

do you have to provide a username/password or token when you try to access the drive now?

I do but it's through the proprietary GUI of the binary which has no CLI or API I can use.

[–] [email protected] 1 points 3 weeks ago (1 children)

then strace might help if we're lucky enough to get something like memory addresses.

strace can be very verbose and requires a lot of knowledge that i doubt i can share through comments back and forth.

is creating an intermediary like others have commented on in this post an option? they're automatically easier and faster than strace and there's no gaurantee that strace will show us the information we need.

[–] [email protected] 1 points 3 weeks ago (1 children)

strace can be very verbose and requires a lot of knowledge that i doubt i can share through comments back and forth.

No worries. Thank a lot nonetheless.

is creating an intermediary like others have commented on in this post an option?

What do you mean by intermediary? Do you mean syncing the files with the VM and then sharing the synced copy with the host?That wouldn't work since my drive is smaller than the cloud drive and I need all the files on-demand.

[–] [email protected] 2 points 3 weeks ago (1 children)

What do you mean by intermediary? Do you mean syncing the files with the VM and then sharing the synced copy with the host?That wouldn’t work since my drive is smaller than the cloud drive and I need all the files on-demand.

that's one way. do you need them all at the same time? are they mostly the same size and type?

[–] [email protected] 1 points 3 weeks ago (1 children)

do you need them all at the same time?

I need to access all files conveniently and transparently depending on what I need at work in that particular moment.

are they mostly the same size and type?

Hard no.

[–] [email protected] 1 points 3 weeks ago (1 children)

sshfs might work if your fuse drive is mounted with options that will let it be shared and you have sudo access to enable sshfs. also ssh access is a requirement.

how is it mounted now? it should also be in that same mount printout and usually at the end of the line inside parenthesis.

[–] [email protected] 1 points 3 weeks ago (1 children)

rw,nosuid,nodev,relatime,user_id=0,group_id=0

[–] [email protected] 1 points 3 weeks ago (1 children)

user_id=0,group_id=0

do you have sudo access and are there any rules in /etc/sudo* that match your username or any of your groups? which distribution?

[–] [email protected] 1 points 3 weeks ago (1 children)

Since originally writing the post I have switched to a rootless podman container. Running it how I did before (inside a VM) would simply yield user_id=1000,group_id=1000 I think.

[–] [email protected] 1 points 3 weeks ago (1 children)

that implies that you're not using the binary anymore since you're in a container; is it using an overlay fs?

[–] [email protected] 1 points 3 weeks ago (1 children)

I am using the binary. Just running it inside a container instead of a VM.

overlay fs?

Yes.

[–] [email protected] 1 points 3 weeks ago (1 children)

so the drive isn't mounted when the container starts; but you execute it after it started and then the drive is mounted?

[–] [email protected] 1 points 3 weeks ago (1 children)

Yes.

[–] [email protected] 1 points 3 weeks ago

i've never seen a workflow like that so i don't think i can help you with the container.

if getting it from the host os an option, then it makes sense to see if it's possible and something like a sudoer rule or selinux could prevent that; my last question was my attempt to ascertain this.