fdisk does not show boot flag

This is because of GPT.

On my Ubuntu 16.04 LTS system fdisk -l /dev/sda shows the following:

Disk /dev/sda: xxx GiB, yyyyyyyyyyyyy bytes, zzzzzzzzz 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
**Disklabel type: gpt**
Disk identifier: AAAAAAAA-BBBB-CCCC-DDDD-EEEEEEEEEEEE

Device         Start       End   Sectors   Size Type
/dev/sda1       2048    616447    614400   300M EFI System
...

But sudo parted /dev/sda shows almost the same:

(parted) p
Model: ATA ... (scsi)
Disk /dev/sda: xxxGB
Sector size (logical/physical): 512B/512B
**Partition Table: gpt**
Disk Flags: 

Number  Start   End     Size    File system     Name                          Flags
 1      1049kB  316MB   315MB   fat32           EFI system partition          **boot**, esp
...

So parted correctly shows boot flag.