# Enabling `systemd` Debug Shell During Boot To diagnose `systemd` related boot issues, you can enable early shell access during boot. Perform the following steps to enable early shell access: 1. Restart the Photon OS machine or the virtual machine running Photon OS. When the Photon OS splash screen appears, as it restarts, type the letter `e` quickly. 1. Append `systemd.debug-shell=1` to the kernel command line. Optionally, to change logging level to debug, you can append `systemd.log_level=debug`. 1. Press `F10` to proceed with the boot. 1. Press `Alt+Ctrl+F9` to switch to `tty9` to access the debug shell.