Eskil

        createdirectory - deletefile - removedirectory - utime {
            # Read-only, always error
        }
    }
    vfs::filesystem posixerror $::vfs::posix(EACCES)
    return -code error $::vfs::posix(EACCES)
}

# Transfer a VcsVfs mount point to another Thread.
# TclVfs mounts are thread local.
# If no mount point is given, tranfer all current mount points
proc vcsvfs::transfer {threadId {mountpoint {}}} {
    variable mpoints
    thread::send -async $threadId "package require vcsvfs"
    if {$mountpoint eq ""} {
        set data $mpoints
    } else {
        set data [dict create $mountpoint [dict get $mpoints $mountpoint]]
    }
    # Data might be large. Is that a problem? Is there a more efficient way?
    thread::send -async $threadId [list vcsvfs::Receive $data]
}

# Create mount(s) from received data
proc vcsvfs::Receive {data} {
    variable mpoints
    foreach mountpoint [dict keys $data] {
        dict set mpoints $mountpoint [dict get $data $mountpoint]
        vfs::filesystem mount $mountpoint [list vcsvfs::Vfs]
    }
}

##################################################################
# Test structure
##################################################################
if 0 {
# File traversing stuff from wiki...
proc ftw_1 {{dirs .}} {