root@localhost:~# SNAP_CONFINE_DEBUG=1 test-snapd-tools.echo 
DEBUG: security tag: snap.test-snapd-tools.echo
DEBUG: executable:   /usr/lib/snapd/snap-exec
DEBUG: confinement:  non-classic
DEBUG: base snap:    core
DEBUG: apparmor label on snap-confine is: /usr/lib/snapd/snap-confine
DEBUG: apparmor mode is: enforce
DEBUG: checking if the current process shares mount namespace with the init process
DEBUG: re-associating is not required
DEBUG: creating lock directory /run/snapd/lock (if missing)
DEBUG: opening lock directory /run/snapd/lock
DEBUG: opening lock file: /run/snapd/lock/.lock
DEBUG: sanity timeout initialized and set for three seconds
DEBUG: acquiring exclusive lock (scope (global))
DEBUG: sanity timeout reset and disabled
DEBUG: ensuring that snap mount directory is shared
DEBUG: unsharing snap namespace directory
DEBUG: creating namespace group directory /run/snapd/ns
DEBUG: namespace group directory does not require intialization
DEBUG: releasing lock (scope: (global))
DEBUG: creating lock directory /run/snapd/lock (if missing)
DEBUG: opening lock directory /run/snapd/lock
DEBUG: opening lock file: /run/snapd/lock/test-snapd-tools.lock
DEBUG: sanity timeout initialized and set for three seconds
DEBUG: acquiring exclusive lock (scope test-snapd-tools)
DEBUG: sanity timeout reset and disabled
DEBUG: initializing mount namespace: test-snapd-tools
DEBUG: opening namespace group directory /run/snapd/ns
DEBUG: initializing new namespace group test-snapd-tools
DEBUG: forking support process for mount namespace capture
DEBUG: forked support process has pid 5306
DEBUG: unsharing the mount namespace
DEBUG: scratch directory for constructing namespace: /tmp/snap.rootfs_AsIoH2
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: pivot_root /tmp/snap.rootfs_AsIoH2 /tmp/snap.rootfs_AsIoH2//var/lib/snapd/hostfs
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: rmdir /var/lib/snapd/hostfs//tmp/snap.rootfs_AsIoH2
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: sc_setup_mount_profiles: test-snapd-tools
DEBUG: opening current mount profile /run/snapd/ns/snap.test-snapd-tools.fstab
cannot open current mount profile: /run/snapd/ns/snap.test-snapd-tools.fstab: Permission denied
root@localhost:~# DEBUG: forked support process has pid 0
DEBUG: changing apparmor hat of the support process for mount namespace capture
DEBUG: changing apparmor hat to mount-namespace-capture-helper
DEBUG: ensuring that parent process is still alive
DEBUG: parent process has already terminated