Packing project content fails if there are UNIX domain sockets

[thp-canonical]

If there's any stray UNIX domain sockets in the project directory, Spread fails to pack the project.

To reproduce this issue, create a socket (you can Ctrl+C the command as soon as it's started, we just want the side effect of creating a socket):

nc -lkU foo.sock

With this in place, trying to run spread fails (example project has a LXD backend, but this issue is most likely independent of backend):

spread -vv lxd

The error message:

2024-02-05 15:15:39 Error packing project content for delivery: cannot pack project tree: tar: foo.sock: socket ignored

As a workaround, we currently run find . -type s -delete before running spread to remove any UNIX domain sockets.

GNU tar supports configurable warning messages using --warning= with:

              file‐ignored
                     "%s: Unknown file type; file ignored"
                     "%s: socket ignored"
                     "%s: door ignored"

The file-ignored warning ignores:

• Unknown file types (see calls to unknown_file_error() in src/create.c in tar's source)
• UNIX domain sockets
• Doors, a Solaris-specific concept

It seems like one could add --warning=no-file-ignored to work around this issue:

diff --git a/spread/runner.go b/spread/runner.go
index c84ff63..ebf4b00 100644
--- a/spread/runner.go
+++ b/spread/runner.go
@@ -277,7 +277,7 @@ func (r *Runner) prepareContent() (err error) {
                return fmt.Errorf("cannot remove temporary content file: %v", err)
        }

-       args := []string{"c", "--exclude=.spread-reuse.*"}
+       args := []string{"c", "--exclude=.spread-reuse.*", "--warning=no-file-ignored"}
        if r.project.Repack == "" {
                args[0] = "cz"
        }

In my local tests, this fixed the issue and lets spread pack the local tree, ignoring any UNIX domain sockets.

[ZeyadYasser]

@thp-canonical you could use the exclude config in spread.yaml to exclude any unwanted files (if their pattern is knowm), please check https://github.com/snapcore/spread/blob/master/README.md#including.

[thp-canonical]

@thp-canonical you could use the exclude config in spread.yaml to exclude any unwanted files (if their pattern is know), please check https://github.com/snapcore/spread/blob/master/README.md#including.

cc @paul-rodriguez would that work for you?