Backup Partition for PicOS

Backup partition for PicOS:

PowerPc Platform:
We use backup partitions for PicOS to upgrade the system and recover PicOS. Usually users need to reserve about 400 MB for partition 2(eg:sda2). The rest of the SD card belongs to partition 1(eg：sda1). If the size of the SD card is 2 GB, partition 1 should be 1.6GB (1600M) and partition 2 is 400M.

Command (m for help): p
Disk /dev/sda: 8004 MB, 8004304896 bytes
247 heads, 62 sectors/track, 1020 cylinders, total 15633408 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/sda1 62 12603421 6301680 83 Linux             ------the primary partition for PicOS
/dev/sda2 12603422 15620279 1508429 83 Linux         ------the backup partition for PicOS

X86 platform:
There are two partitioning ways used with ONIE, GPT and MBR. With GPT partitioning, the sda1/2MB, is allocated to GRUB as BOOT PARTITION. The second partition is used by ONIE itself. The 3rd or others are free, and can be used by NOS. In this mode, the 3rd partition is allocated to PICOS GRUB, for the grub bootup config files. 4th and 5th are for PicOS and PicOS-BACKUP. When the user runs uninstall from ONIE, all partitions except 1st and 2nd are reserved, all NOS are wiped out. With MBR partitioning mode (which is not recommended), the GRUB boot codes are saved before MBR sector and first partition, the first partition is used by ONIE itself. PicOS begins from the 2nd partition for PicOS-GRUB, PicOS and PicOS-BACKUP partitions.

eg:(With MBR)

/dev/sda1: LABEL="ONIE-BOOT" UUID="08ae2c6a-6f14-498f-8e13-d0e7c0a567c1"
/dev/sda3: LABEL="PicOS" UUID="b2735e76-8594-41b9-87e7-d25113dc22f7"        ------the primary partition for PicOS
/dev/sda2: LABEL="PICOS-GRUB" UUID="ca79674b-70fc-4540-b9ef-c98c3afadce3"    
/dev/sda4: LABEL="PICOS-BAK" UUID="92028225-403a-44d4-a40e-25e26d46373b"     ------the backup partition for PicOS

eg:(with GPT)

Disk /dev/sda: 15649200 sectors, 7.5 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 1687245E-B39A-48E5-860B-D7967A67FBE8
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 15649166
Partitions will be aligned on 1-sector boundaries
Total free space is 8547665 sectors (4.1 GiB)
Number Start (sector) End (sector) Size Code Name
1 2048 6143 2.0 MiB EF02 GRUB-BOOT
2 6144 268287 128.0 MiB 3000 ONIE-BOOT
3 268288 1244140 476.5 MiB 0700 PICOS-GRUB
4 1244141 5150390 1.9 GiB 0700 PicOS            -----the primary partition for PicOS
5 5150391 7103515 953.7 MiB 0700 PICOS-BAK       ------the backup partition for PicOS