A development team asks an engineer to guarantee the persistency of journal log files across system reboots. Which of the following commands would accomplish this task?

`grep -i auto /etc/systemd/journald.conf` only searches for the string 'auto' and does not modify the configuration for persistence.

`cat /etc/systemd/journald.conf | awk '(print $1,$3)'` merely displays parts of the configuration file and does not implement any changes to ensure log persistence.

The `sed -i 's/auto/persistent/g' /etc/systemd/journald.conf` command modifies the `journald.conf` file to change the `Storage` setting from `auto` to `persistent`, which configures systemd to store logs permanently on disk. The subsequent `sed -i 'persistent/s/^#//q'` command ensures that the `Storage=persistent` line is uncommented if it was previously commented out, making the setting active; restarting `systemd-journald.service` applies these changes.

`journalctl --list-boots` displays boot journal entries, which would be empty or incomplete if persistence is not configured, and restarting the service alone without configuration changes will not enable persistence.