Add {{.TempDir}} and {{.GlobalTempDir}} variables to host templates

[jandubois]

Allows writing the /tmp/lima mount as

mounts:
- location: "{{.Temp}}/lima"
  mountPoint: /tmp/lima

Note that on macOS this would use $TMPDIR and not /tmp, so would be a change in behaviour. It would not affect existing instances though.

[afbjorklund]

Do you need to model "the real" $TMPDIR, or should it be something like $LIMA_TEMP instead?

One concern was that there are many users sharing the /tmp/lima location, on a shared server.

[arixmkii]

This made default.yaml compatible with Windows. I managed to create and start VM w/o changes to template.

Output of the mount command:

C:\msys64\home\Arthu\gitrepos\lima\_output\bin>limactl shell default mount | find "sshfs"
time="2025-03-08T20:21:48+02:00" level=warning msg="treating lima version \"e0487475.m\" from \"C:\\\\Users\\\\Arthu\\\\.lima\\\\default\\\\lima-version\" as very latest release"
bash: line 1: cd: /mnt/c/msys64/home/Arthu/gitrepos/lima/_output/bin: No such file or directory
:/mnt/c/Users/Arthu on /mnt/c/Users/Arthu type fuse.sshfs (ro,nosuid,nodev,relatime,user_id=1000,group_id=1000,allow_other)
:/mnt/c/Users/Arthu/AppData/Local/Temp/lima on /tmp/lima type fuse.sshfs (rw,nosuid,nodev,relatime,user_id=1000,group_id=1000,allow_other)

The /mnt/ prefixes come from WSL2 Alpine tools container (wslpath instead of cygpath), which I use for running QEMU. I'm yet to figure out required fixes to run it with Git bash msys2 stack (mux modes are not supported in msys2 OpenSSH).

[arixmkii]

9p mounts

C:\msys64\home\Arthu\gitrepos\lima\_output\bin>limactl shell default mount | find "9p"
time="2025-03-08T20:36:53+02:00" level=warning msg="treating lima version \"e0487475.m\" from \"C:\\\\Users\\\\Arthu\\\\.lima\\\\default\\\\lima-version\" as very latest release"
bash: line 1: cd: /mnt/c/msys64/home/Arthu/gitrepos/lima/_output/bin: No such file or directory
mount0 on /mnt/c/Users/Arthu type 9p (ro,relatime,cache=8f,access=client,msize=131072,trans=virtio)
mount1 on /tmp/lima type 9p (rw,relatime,cache=5,access=client,msize=131072,trans=virtio)

[jandubois]

I'm going to leave this PR open (and in draft mode) because I think adding the {{.Temp}} variable and normalizing mountpoints is something we should eventually merge.

But the change to templates/default.yaml seems wrong to me and should not be merged! We need further discussion to figure out how to deal with this. I'll be offline from Mar 13 to 31, so can't participate until next month.

[jandubois]

I've rebased this PR on latest master to solve the merge conflicts. The updated mount location is now localized to just template://_default/mounts.

This PR does introduce a user-visible change, in that /tmp/lima inside the VM is now mounted to $TMPDIR/lima on a Linux or macOS host. It will not change existing instances.

I'm undecided if this is acceptable or not.

[AkihiroSuda]

For compatibility {{ .Temp }} should use /tmp on macOS.
Probably we should have {{ .TempEnv }} (or {{ .TempDynamic }}) for $TMPDIR

[jandubois]

For compatibility {{ .Temp }} should use /tmp on macOS.

I assume you meant Unix, not macOS. os.TempDir() will use TMPDIR on Linux too.

Probably we should have {{ .TempEnv }} (or {{ .TempDynamic }}) for $TMPDIR

How about we use {{ .Tmp }} for /tmp and {{ .TmpDir }} for $TMPDIR, to make it easier to remember?

On Windows both variables would be the same.

[AkihiroSuda]

How about we use {{ .Tmp }} for /tmp and {{ .TmpDir }} for $TMPDIR, to make it easier to remember?

To me this sounds like the former one is a file and the latter one is a directory

[jandubois]

How about {{ .GlobalTemp }} for /tmp and {{ .Temp }} for $TMPDIR then?

The GlobalTemp variable really only exists for the sake of the template://_default/mount template to maintain backwards compatibility. So I would rather keep Temp for the version that users should be using.

PS: I think I actually prefer {{ .GlobalTempDir }} and {{ .TempDir }}.

[AkihiroSuda]

PS: I think I actually prefer {{ .GlobalTempDir }} and {{ .TempDir }}.

👍

[AkihiroSuda]

Thanks