man 1 flatpak-enter

FLATPAK ENTER(1)                 flatpak enter                FLATPAK ENTER(1)

NAME
       flatpak-enter - Enter an application or runtime's sandbox

SYNOPSIS
       flatpak enter [OPTION...] INSTANCE COMMAND [ARG...]

DESCRIPTION
       Enter a running sandbox.

       INSTANCE must be either the pid of a process running in a flatpak
       sandbox, or the ID of a running application, or the instance ID of a
       running sandbox. You can use flatpak ps to find the instance IDs of
       running flatpaks.

       COMMAND is the command to run in the sandbox. Extra arguments are
       passed on to the command.

       This creates a new process within the running sandbox, with the same
       environment. This is useful when you want to debug a problem with a
       running application.

       This command works as a regular user if the system support unprivileged
       user namespace. If that is not available you need to run run it like:
       sudo -E flatpak enter.

OPTIONS
       The following options are understood:

       -h, --help
           Show help options and exit.

       -v, --verbose
           Print debug information during command processing.

       --ostree-verbose
           Print OSTree debug information during command processing.

EXAMPLES
       $ flatpak enter 15345 sh

SEE ALSO
       flatpak(1), flatpak-run(1) flatpak-ps(1)

flatpak                                                       FLATPAK ENTER(1)