What causes "legacy audit tree contains a redirect or boundary: {child}" in astrid-runtime/astrid?

Remove or replace the symlinked/mounted child with a real directory inside the same filesystem

legacy audit tree contains a redirect or boundary

Error message

legacy audit tree contains a redirect or boundary: {child}

What it means

This error is thrown while validating a legacy audit tree directory. The validator walks the tree and refuses any child that is a symlink, resides on a different filesystem device than the root, or is itself a mountpoint, because such redirects/boundaries could make audit data escape the intended tree or be placed on untrusted storage. It is an InvalidData io::Error naming the offending child path.

Solutions

Remove or replace the symlinked/mounted child with a real directory inside the same filesystem
Move the audit tree entirely onto a single filesystem so no child crosses a device boundary
Identify the offending path from the error message and unmount it (umount <child>) before retrying
Restore the audit directory from backup as plain directories/files

Example fix

// before
ln -s /mnt/big-disk/audit /var/lib/app/audit/events
// after
rm /var/lib/app/audit/events
mkdir /var/lib/app/audit/events

Defensive patterns

Strategy: validation

Validate before calling

for entry in std::fs::read_dir(audit_root)? {
    let p = entry?.path();
    let md = std::fs::symlink_metadata(&p)?;
    if md.file_type().is_symlink() { return Err(format!("symlink: {}", p.display())); }
}

Type guard

fn is_plain_dir(md: &std::fs::Metadata) -> bool {
    md.is_dir() && !md.file_type().is_symlink()
}

Try / catch

match validate_audit_tree(root, root_dev) {
    Err(e) if e.kind() == std::io::ErrorKind::InvalidData => eprintln!("fix audit tree: {e}"),
    Err(e) => return Err(e),
    Ok(()) => {},
}

Prevention

Never symlink directories inside the audit tree
Keep the audit tree on a single filesystem; avoid submounts
Monitor the tree with a cron check for symlinks/mountpoints
Document the audit directory as managed state

When it happens

Trigger: Calling the audit-tree validation routine (e.g. when opening or migrating a legacy audit store) when any child entry of the tree is a symlink, has a different st_dev than the tree root, or is a mounted filesystem.

Common situations: Users replaced an audit log directory with a symlink to another disk; a subdirectory is a separate mount (e.g. tmpfs or NFS bind mount); container images where parts of the audit tree come from overlay mounts.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of astrid-runtime/astrid@affd8760f4 (2026-09-09). Data as JSON: /api/errors/c2c370284e7291a8. Report an issue: GitHub.

Appendix: source

Thrown at crates/astrid-kernel/src/lib.rs:4347

    }
    if audit_tree_device(&metadata) != root_device || audit_mountpoint(path)? {
        return Err(std::io::Error::new(
            std::io::ErrorKind::InvalidData,
            format!(
                "legacy audit tree crosses a filesystem or mount boundary: {}",
                path.display()
            ),
        ));
    }
    astrid_core::platform_fs::verify_no_redirects(path)?;
    for entry in std::fs::read_dir(path)? {
        let child = entry?.path();
        let child_metadata = std::fs::symlink_metadata(&child)?;
        if child_metadata.file_type().is_symlink()
            || audit_tree_device(&child_metadata) != root_device
            || audit_mountpoint(&child)?
        {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                format!(
                    "legacy audit tree contains a redirect or boundary: {}",
                    child.display()
                ),
            ));
        }
        if child_metadata.is_dir() {
            validate_audit_tree(&child, root_device)?;
        } else if child_metadata.is_file() {
            astrid_core::platform_fs::verify_no_redirects(&child)?;
        } else {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                format!(
                    "legacy audit tree contains a special file: {}",
                    child.display()
                ),

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