UbiOS

UbiOS (Ubiquiti OS) Ubiquiti's new linux distribution which is expected to be gradually deployed in all their devices. Thensystem is based on Buildroot project and main elements are written in C++.

Technologies used: Buildroot, C, C++, various linux tools and daemons

Internal Disk Layout

Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt

Device       Start      End  Sectors  Size Type
/dev/sdb1     2048   133119   131072   64M Linux filesystem
/dev/sdb2   133120  2230271  2097152    1G Linux filesystem
/dev/sdb3  2230272  4327423  2097152    1G Linux filesystem
/dev/sdb4  4327424  4589567   262144  128M Linux filesystem
/dev/sdb5  4589568  4655103    65536   32M Linux filesystem
/dev/sdb6  4655104 30777310 26122207 12.5G Linux filesystem

FS details

Partition	Mount point
/dev/sdb1
/dev/sdb2
/dev/sdb3	root
/dev/sdb4	/mnt/persistent
/dev/sdb5
/dev/sdb6	/mnt/data

Swap is in a ~7G zram disk. Memory limit is set to around ~3G

Boot Sequence

Built upon Alpine v2 but using BusyBox for init

Bootloader

Kernel

Init

Init process via BusyBox

init process reads ⁄etc⁄inittab for sysinit entires
init calls ⁄etc⁄init.d⁄rcS
rcS executes Start scripts in ⁄etc⁄init.d in order

Startup Scripts

File Name	Description
S95unifi-os	Starts Unifi OS Container