gdisk /dev/sdx

GPT fdisk (gdisk) version 0.6.14

Partition table scan:
  MBR: MBR only
  BSD: not present
  APM: not present
  GPT: not present


***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format.
THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by typing 'q' if
you don't want to convert your MBR partitions to GPT format!
***************************************************************


Command (? for help):

Command (? for help): n
Partition number (2-128, default 2): 2
First sector (34-7831518, default = 34) or {+-}size{KMGTP}:
Information: Moved requested sector from 34 to 2048 in
order to align on 2048-sector boundaries.
Use 'l' on the experts' menu to adjust alignment
Last sector (2048-421887, default = 421887) or {+-}size{KMGTP}:
Current type is 'Linux/Windows data'
Hex code or GUID (L to show codes, Enter = 0700): L
0700 Linux/Windows data    0c01 Microsoft reserved    2700 Windows RE
4200 Windows LDM data      4201 Windows LDM metadata  7501 IBM GPFS
7f00 ChromeOS kernel       7f01 ChromeOS root         7f02 ChromeOS reserved
8200 Linux swap            8301 Linux reserved        8e00 Linux LVM
a500 FreeBSD disklabel     a501 FreeBSD boot          a502 FreeBSD swap
a503 FreeBSD UFS           a504 FreeBSD ZFS           a505 FreeBSD Vinum/RAID
a800 Apple UFS             a901 NetBSD swap           a902 NetBSD FFS
a903 NetBSD LFS            a904 NetBSD concatenated   a905 NetBSD encrypted
a906 NetBSD RAID           ab00 Apple boot            af00 Apple HFS/HFS+
af01 Apple RAID            af02 Apple RAID offline    af03 Apple label
af04 AppleTV recovery      be00 Solaris boot          bf00 Solaris root
bf01 Solaris /usr & Mac Z  bf02 Solaris swap          bf03 Solaris backup
bf04 Solaris /var          bf05 Solaris /home         bf06 Solaris alternate se
bf07 Solaris Reserved 1    bf08 Solaris Reserved 2    bf09 Solaris Reserved 3
bf0a Solaris Reserved 4    bf0b Solaris Reserved 5    c001 HP-UX data
c002 HP-UX service         ef00 EFI System            ef01 MBR partition scheme
ef02 BIOS boot partition   fd00 Linux RAID
Hex code or GUID (L to show codes, Enter = 0700): ef00
Changed type of partition to 'EFI System'

Command (? for help): p
Disk /dev/sdd: 7831552 sectors, 3.7 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 669247F2-37F7-4797-98F9-9CE56F7EA8C8
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 7831518
Partitions will be aligned on 2048-sector boundaries
Total free space is 4029 sectors (2.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1          421888         7829503   3.5 GiB     0700  Linux/Windows data
   2            2048          421887   205.0 MiB   EF00  EFI System

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed, possibly destroying your data? (Y/N): y
OK; writing new GUID partition table (GPT).
The operation has completed successfully.

ioreg -l -p IODeviceTree | grep firmware-abi

sudo apt-get install <package name>

menuentry "Windows 7" {
        set root='(hd0,gpt1)'
        chainloader /EFI/microsoft/bootmgfw.efi
}

update-grub

/dev/sdb3    /boot/efi    vfat    defaults    0    1

$ ls /dev/disk/by-uuid -lah
total 0
drwxr-xr-x 2 root root 100 Dec  5 09:12 .
drwxr-xr-x 6 root root 120 Dec  5 09:12 ..
lrwxrwxrwx 1 root root  10 Dec  5 09:12 27fae347-4c7f-45cb-92d6-5f3d410599a1 -> ../../sda3
lrwxrwxrwx 1 root root  10 Dec  5 09:12 4405-64C8 -> ../../sda1
lrwxrwxrwx 1 root root  10 Dec  5 09:12 5243e250-8da5-4fea-aa63-61466022661d -> ../../dm-0

UUID=4405-64C8  /boot/efi       vfat    defaults        0       1