automatic shared folder mounting in VMs

[phabricator-migrator]

Information

ID: 144
PHID: PHID-TASK-l4bigtpt4634scsvdow6
Author: Patrick
Status at Migration Time: resolved
Priority at Migration Time: Normal

Description

Migrated from:
https://github.com/Whonix/Whonix/issues/223

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Where we are:

The /mnt/shared folder gets already created by the shared-folder-help package.

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Non-solutions:

• There is no /etc/fstab.d.
• Patching /etc/fstab by a script seems too fragile.

TODO:

Implement this using systemd.

For VirtualBox, use Requires=vboxguest [or so, just do nothing if vboxguest or just output an info if not installed], then run.

mount -t vboxsf -o uid=1000,gid=1000 shared /mnt/shared

For kvm/qemu/libvirt, check necessary conditions(?), then run.

mount -t 9p -o trans=virtio shared /mnt/shared -oversion=9p2000.L

Comments

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HulaHoop

2015-05-03 00:42:40 UTC

With the migration to systemd, is it now easier to add this?

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Patrick

2015-05-03 04:04:59 UTC

Neither easier nor harder.

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HulaHoop

2015-06-12 23:43:03 UTC

fstab.d should be available in the libmount version in Jessie:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=666163

A bug in the kernel causes the regular expression for mounting 9p shares to fail. A tested workaround works in /etc/fstab :

shared /mnt/shared 9p x-systemd.automount,x-systemd.device-timeout=10,trans=virtio,version=9p2000.L,rw 0 0

https://bugzilla.redhat.com/show_bug.cgi?id=1184122

Tests with fstab.d giving me problems. It could be a matter of not knowing how it works. I first didn’t know that there should be a directory called fstab.d and not a file. Apparently configuration files in there should be named a special way:

/etc/fstab.d/00_header.fstab, /etc/fstab.d/50_middle.fstab, /etc/fstab.d/99_end.fstab

A different option for share mounting is /sbin/mount.filetype for example /sbin/mount.nfs. Needs more research doesn’t seem as easy as dropping a text file in sbin

Can I include another file in fstab - Unix & Linux Stack Exchange

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Patrick

2015-06-13 02:48:20 UTC

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=666163 says fstab.d support has been removed. Not a great long term solution.

#systemd could help. It supports ConditionVirtualization=kvm. Has tmpfiles.d. + Running the mount command. Should be doable.

Anyone feel free to submit a tested patch.

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HulaHoop

2015-06-13 14:48:06 UTC

systemd can understand mount entries but they still have to be specified in /etc/fstab which won’t solve anything.

More information on fstab.d:

Turns out fstab.d is not supported by default in libmount however the mount option can take an alternate mount table file/directory as specified in a command. Please read the linked answer that I’m trying to paraphrase here:

Why can't mount read files in "/etc/fstab.d/"? - Ask Ubuntu

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Alternatives to system-wide fstab is to tell udsisks to mount a directory for a user account upon login:

Do "personal fstab" files exist for user accounts? - Ask Ubuntu

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Patrick

2015-06-13 14:58:06 UTC

If the manual mount command that does not involve /etc/fstab, i.e. mount -t 9p -o trans=virtio shared /mnt/shared -oversion=9p2000.L work for you in terminal, then a systemd unit file could do the same. Also without requiring /etc/fstab.

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HulaHoop

2015-06-13 19:39:16 UTC

Excellent example of shared folder mounting with systemd files in Arch documentation. It will take changing them from vmware to suit KVM and drop them in the same paths for testing:

VMware/Install Arch Linux as a guest - ArchWiki

Notes:

filetype=9p

These units must be “enabled” to make them automatically start with subsequent system startups

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Command cheat sheet:

systemd - ArchWiki

Show the status of a unit, including whether it is running or not:

$ systemctl status unit

Check whether a unit is already enabled or not:

$ systemctl is-enabled unit

Enable a unit to be started on bootup:

systemctl enable unit

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Patrick

2015-06-13 19:29:45 UTC

Nice. Much better than manually running mount from systemd.

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HulaHoop

2015-06-13 21:21:44 UTC

How far I’ve gone:
I managed to debug errors until I corrected the parameters in the unit files so they should be correct. The remaining error has something to do with the 9p kernel module and I’m not sure where to go from here.

host mount[8341]: mount: mount(2) failed: No such file or directory
host kernel: 9pnet_virtio: no channels available
host systemd[1]: mnt-shared.mount mount process exited, code=exited status=32
host systemd[1]: Failed to mount Load KVM shared folders.

/etc/systemd/system/mnt-shared.mount

[Unit]
Description=Load KVM shared folders
ConditionPathExists=/mnt/shared
ConditionVirtualization=kvm

[Mount]
What=/mnt/shared
Where=/mnt/shared
Type=9p
Options=defaults
DirectoryMode=0777
TimeoutSec=10

[Install]
WantedBy=multi-user.target

/etc/systemd/system/mnt-shared.automount

[Unit]
Description=Load KVM shared folders
ConditionPathExists=/mnt/shared
ConditionVirtualization=kvm

[Automount]
Where=/mnt/shared
DirectoryMode=0777

[Install]
WantedBy=multi-user.target 

Debugging:
Run as root

systemctl daemon-reload
systemctl start mnt-shared.mount
journalctl -xn

q to quit detailed error report by journalctl

edit the files once again and save thenreload daemons and so on.

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HulaHoop

2015-06-13 21:36:26 UTC

This option is dead because of some rare bug. There are only 4 search results for it and none of the situations really applies to our setup here.

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HulaHoop

2015-06-14 00:43:32 UTC

A solution you probably won’t like is patching the fstab file directly.

Something based on the third method on here:
http://blog.allanglesit.com/2012/05/bash-programmatically-add-entries-in-fstab/

Followed by column -t /etc/fstab to make it reader friendly:
text processing - How to align fstab entries easily - Unix & Linux Stack Exchange

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Patrick

2015-06-14 00:53:37 UTC

HulaHoop (HulaHoop):

A solution you probably won’t like is patching the fstab file directly.

Indeed.

Have systemd run the ‘mount’ command would be better and should be possible.

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HulaHoop

2015-06-14 13:32:29 UTC

Ok I see what you’re talking about.

The mount command is placed in a regular script file and then a custom systemd service is configured to execute it on startup:

How to write startup script for Systemd? - Unix & Linux Stack Exchange

I can do the systemd service file part but I’m unsure as to how the script should look like. If its as simple as pasting the command I use in there, no problem.

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Patrick

2015-06-14 14:49:36 UTC

Yes, somewhat.

I don’t think you need a separate script. Instead of running a single
line script, you could try running the mount command directly from the
systemd unit file.

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HulaHoop

2015-06-14 23:48:13 UTC

Great news! automatic shared folders is now achieved

I used this as an example:
https://lukas.zapletalovi.com/posts/2013/execute-command-during-start-with-systemd/

Two systemd service files were created under /etc/systemd/system/

To enable and start them:

sudo systemctl enable service-name
sudo systemctl start service-name

mnt-shared-kvm.service

[Unit]
Description=Mounts KVM shared folder during start
ConditionPathExists=/mnt/shared
ConditionVirtualization=kvm

[Service]
Type=oneshot
ExecStart=/bin/mount -t 9p -o trans=virtio shared /mnt/shared -oversion=9p2000.L
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

mnt-shared-vbox.service

[Unit]
Description=Mounts VirtualBox shared folder during start
ConditionPathExists=/mnt/shared
ConditionVirtualization=oracle
After=vboxguest.service
After=virtualbox-guest-utils.service

[Service]
Type=oneshot
ExecStart=/bin/mount -t vboxsf -o uid=1000,gid=1000 shared /mnt/shared
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

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Patrick

2015-06-14 23:59:35 UTC

Nice!

TODO:

• In section [Unit] it should probably use After= something. I.e. make it run after VBox / KVM guest additions.
• debian/rules modifications
• debian/control modifications
• use /lib/systemd/system/
• commit to shared-folder-help package
• build package, test if it actually works

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HulaHoop

2015-06-14 23:13:45 UTC

What is the name of the systemd vbox guest additions service so I can add it? KVM does not rely on spice or a guest additions equivalent to share folders.

A vbox guest additions dependency only makes sense if its installed by default.

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Patrick

2015-06-14 23:45:41 UTC

How to find out? Look manually into /etc/init.d/virtualbox-guest-utils
(or systemd unit files if it had those) and/or ‘grep -i provides
/etc/init.d/virtualbox-guest-utils’.

After=vboxguest.service
After=virtualbox-guest-utils.service

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HulaHoop

2015-06-14 23:50:07 UTC

OK I edited my comment and added those in under the Unit section.

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HulaHoop

2015-06-21 17:34:21 UTC

https://github.com/Whonix/shared-folder-help/pull/1
https://github.com/Whonix/shared-folder-help/pull/2
https://github.com/Whonix/shared-folder-help/pull/3
https://github.com/Whonix/shared-folder-help/pull/4

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Patrick

2015-08-06 15:27:53 UTC

Merged. Requires testing when new test images get available.

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Patrick

2015-11-20 15:17:40 UTC

! In T144#6289, @Patrick wrote:
Merged. Requires testing when new test images get available.

https://forums.whonix.org/t/whonix-12-0-0-3-2-rc-testers-wanted/

Does it work in KVM?

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Patrick

2015-11-29 18:38:25 UTC

do not let systemd service enter failed state of host config has not been applied:
https://github.com/Whonix/shared-folder-help/commit/24143991888ab900effe4b11f7eb55172af6793d

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Patrick

2016-03-16 15:42:46 UTC

@HulaHoop reported it works in KVM.

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Patrick

2016-05-14 14:40:08 UTC

https://github.com/Whonix/shared-folder-help/commit/d797f2ad9e4f385d4873ad137056a1e9807b9ecb