Greetings Bhupesh, > Sent: Thursday, August 30, 2018 at 6:24 PM > From: "Bhupesh Sharma" <[email protected]> > To: daggs <[email protected]> > Cc: [email protected] > Subject: Re: question regarding partition detection on efi boot > > Hi, > > On Thu, Aug 30, 2018 at 7:54 PM, daggs <[email protected]> wrote: > > Greetings, > > > > I apologize if this isn't the right location to ask. as you guys wrote efi > > support for linux I've thought you might be able to help me fill the gaps > > on this issue. > > > > we have a production server with sles12 sp3 installed on it. > > the partition table on the machine is this: > > # fdisk -l /dev/sda > > Disk /dev/sda: 223.6 GiB, 240057409536 bytes, 468862128 sectors > > Units: sectors of 1 * 512 = 512 bytes > > Sector size (logical/physical): 512 bytes / 4096 bytes > > I/O size (minimum/optimal): 4096 bytes / 4096 bytes > > Disklabel type: dos > > See the Disklabel type: dos. If it shows dos, AFAICR it means it is > MBR schema (and not a GPT schema) > > > Disk identifier: 0xf9a6b446 > > > > Device Boot Start End Sectors Size Id Type > > /dev/sda1 * 2048 4192255 4190208 2G 83 Linux > > /dev/sda2 4192256 468860927 464668672 221.6G 83 Linux > > > > mount output is as follows: > > s2600wf-0:~ # mount | grep boot > > /dev/sda2 on /boot/grub2/i386-pc type btrfs > > (rw,relatime,ssd,space_cache,subvolid=260,subvol=/@/boot/grub2/i386-pc) > > /dev/sda1 on /boot/efi type vfat > > (rw,relatime,fmask=0002,dmask=0002,allow_utime=0020,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro) > > /dev/sda2 on /boot/grub2/x86_64-efi type btrfs > > (rw,relatime,ssd,space_cache,subvolid=261,subvol=/@/boot/grub2/x86_64-efi) > > May be you should try 'gdisk' instead to list the GPT partitions in > addition to the MBR ones. Following is an output from my Fedora28 EFI > machine: > > $ sudo gdisk -l /dev/sda > GPT fdisk (gdisk) version 1.0.4 > > Partition table scan: > MBR: protective > BSD: not present > APM: not present > GPT: present > > Found valid GPT with protective MBR; using GPT. > Disk /dev/sda: 1953525168 sectors, 931.5 GiB > Model: TOSHIBA DT01ACA1 > Sector size (logical/physical): 512/4096 bytes > Disk identifier (GUID): E01AB4D7-2DA7-4300-9CE8-FD573801C1DC > Partition table holds up to 128 entries > Main partition table begins at sector 2 and ends at sector 33 > First usable sector is 34, last usable sector is 1953525134 > Partitions will be aligned on 2048-sector boundaries > Total free space is 3437 sectors (1.7 MiB) > > Number Start (sector) End (sector) Size Code Name > 1 2048 411647 200.0 MiB EF00 EFI System Partition > 2 411648 2508799 1024.0 MiB 8300 > 3 2508800 1953523711 930.3 GiB 8E00 > > Looking at the output you can make out the 'EFI System Partition' entry. > Also if you see something like: > > *************************************************************** > Found invalid GPT and valid MBR; converting MBR to GPT format > in memory. > *************************************************************** > > then you have a MBR style disk.. > the partition table isn't gpt, it is mbr.
> > and here is the content of /sys/firmware/efi/: > > s2600wf-0:~ # ll /sys/firmware/efi/ > > total 0 > > -r--r--r-- 1 root root 4096 Aug 29 03:19 config_table > > drwxr-xr-x 2 root root 0 Aug 29 03:17 efivars > > -r--r--r-- 1 root root 4096 Aug 29 03:19 fw_platform_size > > -r--r--r-- 1 root root 4096 Aug 29 03:19 fw_vendor > > -r--r--r-- 1 root root 4096 Aug 29 03:19 runtime > > drwxr-xr-x 11 root root 0 Aug 29 03:19 runtime-map > > -r-------- 1 root root 4096 Aug 29 03:17 systab > > drwxr-xr-x 140 root root 0 Aug 29 03:19 vars > > > > afaik, if the partition table is mbr, then for efi to boot, the boot > > partition must be of type EF. in this case it isn't so I was wondering how > > the system boots in efi? how does the bios detects it? > > am I missing something? > > It depends on the BIOS on your machine. Please see > <https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface#UEFI_booting> > for details. Interesting, so according to the link, if <vfat>/EFi/BOOT/boot<arch>.efi exists, the bios will try to boot it as efi (assuming that the bios supports it). I wonder if this can be found in the spec, will have to take a look. this is true fir gto partition tables too? > > Thanks, > Bhupesh >
