The /boot directory is used to store OTA update data and is the mount point for the upgrade partition for an OTA update.

Usually empty, except for OTA update data.

These contents are added when in update or restore mode:

• apticket.der
• iBEC
• kernelcache
• ramdisk
• devicetree
• applelogo

In the iBoot source code, the 'upgrade.c' file defines the directory's contents, such as iBEC and the ramdisk.