Sample systemd setup to mount efi partitions and sync them in a service on shutdown

etc_systemd_system_sync-efi.service

[Unit]
Description=Sync EFI partitions

[Service]
Type=oneshot
ExecStop=/usr/bin/sync-efi

[Install]
WantedBy=multi-user.target

Sync EFI for systemd: etc_fstab

#sample efi file to mount efi partitions and sync them in a service on shutdown
#UUID are different for each system of course, run blkid to see
UUID=EE08-63AC                             /boot/efi  vfat  utf8,nofail          0  2
UUID=D6DD-B604                             /boot/efi2  vfat  utf8,nofail          0  2
UUID=D725-1927                             /boot/efi3  vfat  utf8,nofail          0  2
UUID=D761-CCBA                             /boot/efi4  vfat  utf8,nofail          0  2

usr_bin_sync-efi

!/bin/bash

# Find all EFI partitions and sync them
for partition in $(egrep "boot/efi[0-9]" /etc/fstab | awk '{ print $2 }'); do
    echo "Syncing EFI partition: $partition"
    rsync -a --delete  /boot/efi $partition
done