13

I normally use fdisk -l to look at partitions. I recently installed ubuntu 17.10 on a computer, and noticed that fdisk is not showing me the boot flag as it used to do. The output now looks for example like this

Device       Start        End    Sectors  Size Type
/dev/sda1     2048    1050623    1048576  512M EFI System
/dev/sda2  1050624 1953523711 1952473088  931G Linux filesystem

I've not been able to find any info on why the boot column is missing, or how to get it back. Any links/info on this?

fdisk --version gives me fdisk from util-linux 2.30.1. I have another computer with version 2.27 (ubuntu 16.04), and this does show me the boot flag.

funklute
  • 233

2 Answers2

7

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.

N0rbert
  • 103,263
0

If you need to find this information programmatically (like I did) this command should do the trick for you. sudo parted -l 2>/dev/null | grep -B7 boot > temp.fil; grep Disk temp.fil; grep boot temp.fil; rm temp.fil

This command produces output similar to this:

Disk /dev/nvme0n1: 120GB
Disk Flags: 
 1      1049kB  577MB  576MB  primary  ntfs         boot

For those who are unfamiliar with these commands, they work together as follows:

from man parted

-l, --list
              lists partition layout on all block devices

this is piped through grep

this was cleaned up by redirecting error output to dev/null with 2>/dev/null to eliminate the error message that my optical drive was generating in parted output.

From man grep

-B NUM, --before-context=NUM
              Print NUM lines of leading context before matching lines.  Places a line containing a group separator (--) between
              contiguous groups of matches.  With the -o or --only-matching option, this has no effect and a warning is given.

I chose to grab the first 7 lines and redirect into a temporary file temp.fil for ease of obtaining the output I required, You may find that you require a different number of lines before the match to get what you need. Each ; indicates the start of a new command. grep Disk temp.fil returns the line in the temporary file that identifies the boot drive and grep boot temp.fil returns the line in the temporary file that identifies the boot partition. The rm temp.fil simply removes the temporary file previously created.

NOTE: This command string will overwrite any file called temp.fil in the current directory and then delete the result. If this is a problem for you change the name accordingly.

Elder Geek
  • 36,752