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CentOS 7 UEFI Install on appliance with mirrored GPT partitions

[GPT, UEFI, Mirror, Raid1]

The following notes are on installing CentOS v7 on a physical appliance with two small SSD's. Every practical step is taken overcome a single disk failure.

Key aspects:

  1. The BIOS is configured for UEFI boot
  2. The installation is done with UEFI boot from a USB flash drive based image (dd the iso onto the drive)
  3. The disks are partitioned with a GUID partition table (GPT)
  4. Linux software RAID 1 (mirror) is used to mirror the partitions (not whole device)
  5. A non-RAIDed UEFI FAT based partition for booting
    1. the 'second' disk has a copy of the files
  6. Anaconda is limited in it's support of creating identical disks
  7. Simple filesystems are used
    1. no xfs, just ext4
    2. no LVM
  8. No hardware RAID

 

 

Template Disk

Install CentOS 7 using anaconda. Manually create the following paritions during the installation:

  • a 100M EFI System Partition (ESP) FAT16 partition
  • a 1G '/boot' ext4 RAID1 partition
  • a 4G swap RAID1 partition
  • 1 12G '/' (root) ext4 RAID1 partition

Ananonda can do everything except helping create a copy/mirror of the EFI partition as parition number one on the secondary disk. Let anaconda partition and work with the second disk, but the next step discards that for the second disk after the installation is complete..

# parted /dev/sda
GNU Parted 3.1
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) unit s
(parted) print
Model: ATA KINGSTON SMS200S (scsi)
Disk /dev/sda: 58626288s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start      End        Size       File system  Name                  Flags
 1      2048s      206847s    204800s    fat16        EFI System Partition  boot
 2      206848s    8402943s   8196096s                                      raid
 3      8402944s   10450943s  2048000s   ext4                               raid
 4      10450944s  35043327s  24592384s                                     raid

 

Remove /dev/sdb from the RAID

The second disk is part of the three RAID mirrors

# cat /proc/mdstat
Personalities : [raid1]
md125 : active raid1 sda4[0] sdb4[1]
      12287872 blocks super 1.2 [2/2] [UU]
      bitmap: 0/1 pages [0KB], 65536KB chunk

md126 : active raid1 sda3[0] sdb2[1]
      1023936 blocks super 1.0 [2/2] [UU]

md127 : active raid1 sda2[0] sdb1[1]
      4095936 blocks super 1.2 [2/2] [UU]

unused devices: <none>

Fail and remote the three partitions from the mirrors:

# mdadm --fail /dev/md125 sdb4
# mdadm --remove /dev/md125 sdb4
# mdadm --fail /dev/md126 sdb2
# mdadm --remove /dev/md126 sdb2
# mdadm --fail /dev/md127 sdb1
# mdadm --remove /dev/md127 sdb1

 Unmount the secondary fat16 filesystem created during the installation:

# umount /boot/efi2
# cat /proc/mdstat
Personalities : [raid1]
md125 : active raid1 sda4[0]
      12287872 blocks super 1.2 [2/1] [U_]
      bitmap: 1/1 pages [4KB], 65536KB chunk

md126 : active raid1 sda3[0]
      1023936 blocks super 1.0 [2/1] [U_]

md127 : active raid1 sda2[0]
      4095936 blocks super 1.2 [2/1] [U_]

unused devices: <none>

Repartition the second disk 

Partition

Use 'parted' to recreate the second device using the dimensions (units of sectors) from the frist device:

# parted /dev/sdb
mktable gpt
unit s mkpart primary fat16 2048s 206847s
mkpart primary ext4  206848s    8402943s
mkpart primary linux-swap  8402944s   10450943s  
mkpart primary ext4  10450944s  35043327s 
name 1 "EFI System Partition"
name 2 /boot
name 3 swap
name 4 /
set 1 boot on
set 2 raid on
set 3 raid on
set 4 raid on
quit

FAT EFI

Create a FAT16 filesystem on the backup EFI boot partition (Note: If the system was being used with Windows then a FAT32 filesystem would be required):

# mkfs.vfat -F 16 -n 'EFI System Partition' /dev/sdb1

Update the '/etc/fstab' with the UUID of the of new FAT filesystem (use 'lsblk -f' to find the id) and then remount the secondary EFI filesystem (which was mounted as '/boot/efi2' during the anaconda install):

# mount -a

Manually copy the EFI files from the first disk to the second:

# cp -av /boot/efi/. /boot/efi2/

Mirrors

Remirror the three partitions to 'boot', swap and '/':

mdadm --add /dev/md125 /dev/sdb4
mdadm --add /dev/md126 /dev/sdb3
mdadm --add /dev/md127 /dev/sdb2

EFI Boot

Ensure both disks are added to the UEFI NVRAM. Using a label that includes the disk serial number (if part of it) is useful:

# efibootmgr -c -d /dev/sdb -g -p 1 -L "CentOS 46034436" -l '\EFI\centos\shim.efi'
# efibootmgr -c -d /dev/sda -g -p 1 -L "CentOS 4603410E" -l '\EFI\centos\shim.efi'

Filesystems

When the system boots in a degraded mode the /boot/efi or /boot/efi2 ESP filesystems may not be available. So that systemd doesn't halt the boot process add a 'nofail' option to the '/etc/fstab' for the two ESP filesystems:

UUID=34d2ee88-3ed3-4aa6-9279-f9733bca95d5 /                       ext4    defaults        1 1
UUID=346ba696-2d7e-4f4d-b56d-4d5d0cf4da21 /boot                   ext4    defaults        1 2
UUID=F6CE-F5D0          /boot/efi               vfat    umask=0077,shortname=winnt,nofail 0 0
UUID=A6B3-2CF2          /boot/efi2              vfat    umask=0077,shortname=winnt,nofail 0 0
UUID=1e4da845-94a2-4672-9505-5cbe5e8e716f swap                    swap    defaults        0 0

Links

Appendices

lsblk

# lsblk -f
NAME      FSTYPE            LABEL          UUID                                 MOUNTPOINT
sda
├─sda1    vfat                             F6CE-F5D0                            /boot/efi
├─sda2    linux_raid_member localhost:swap 32bf0d04-5da1-f473-62f5-1c568b489995
│ └─md127 swap              swap           1e4da845-94a2-4672-9505-5cbe5e8e716f [SWAP]
├─sda3    linux_raid_member localhost:boot 9826d78d-61eb-8315-818f-196cd5e074a5
│ └─md126 ext4              /boot          346ba696-2d7e-4f4d-b56d-4d5d0cf4da21 /boot
└─sda4    linux_raid_member localhost:root 6f2768ed-9df6-643a-0d82-3c5966bfc606
  └─md125 ext4                             34d2ee88-3ed3-4aa6-9279-f9733bca95d5 /
sdb
├─sdb1    vfat              EFI SYSTEM     A6B3-2CF2                            /boot/efi2
├─sdb2    linux_raid_member localhost:swap 32bf0d04-5da1-f473-62f5-1c568b489995
│ └─md127 swap              swap           1e4da845-94a2-4672-9505-5cbe5e8e716f [SWAP]
├─sdb3    linux_raid_member localhost:boot 9826d78d-61eb-8315-818f-196cd5e074a5
│ └─md126 ext4              /boot          346ba696-2d7e-4f4d-b56d-4d5d0cf4da21 /boot
└─sdb4    linux_raid_member localhost:root 6f2768ed-9df6-643a-0d82-3c5966bfc606
  └─md125 ext4                             34d2ee88-3ed3-4aa6-9279-f9733bca95d5 /

EFI Files 

# cp -av /boot/efi/. /boot/efi2/
‘/boot/efi/./EFI/centos’ -> ‘/boot/efi2/./EFI/centos’
‘/boot/efi/./EFI/centos/fonts’ -> ‘/boot/efi2/./EFI/centos/fonts’
‘/boot/efi/./EFI/centos/fonts/unicode.pf2’ -> ‘/boot/efi2/./EFI/centos/fonts/unicode.pf2’
‘/boot/efi/./EFI/centos/grub.cfg’ -> ‘/boot/efi2/./EFI/centos/grub.cfg’
‘/boot/efi/./EFI/centos/gcdx64.efi’ -> ‘/boot/efi2/./EFI/centos/gcdx64.efi’
‘/boot/efi/./EFI/centos/grubx64.efi’ -> ‘/boot/efi2/./EFI/centos/grubx64.efi’
‘/boot/efi/./EFI/centos/BOOT.CSV’ -> ‘/boot/efi2/./EFI/centos/BOOT.CSV’
‘/boot/efi/./EFI/centos/MokManager.efi’ -> ‘/boot/efi2/./EFI/centos/MokManager.efi’
‘/boot/efi/./EFI/centos/shim-redhat.efi’ -> ‘/boot/efi2/./EFI/centos/shim-redhat.efi’
‘/boot/efi/./EFI/centos/shim.efi’ -> ‘/boot/efi2/./EFI/centos/shim.efi’
‘/boot/efi/./EFI/BOOT’ -> ‘/boot/efi2/./EFI/BOOT’
‘/boot/efi/./EFI/BOOT/BOOTX64.EFI’ -> ‘/boot/efi2/./EFI/BOOT/BOOTX64.EFI’
‘/boot/efi/./EFI/BOOT/fallback.efi’ -> ‘/boot/efi2/./EFI/BOOT/fallback.efi’

efibootmgr

# efibootmgr -c -d /dev/sdb -p 1 -L "CentOS" -l '\EFI\centos\shim.efi'
** Warning ** : Boot0000 has same label CentOS
BootCurrent: 0000
Timeout: 1 seconds
BootOrder: 0002,0000,0001
Boot0000* CentOS
Boot0001* UEFI: KINGSTON SMS200S330G
Boot0002* CentOS

gdisk

# gdisk -l /dev/sda
GPT fdisk (gdisk) version 0.8.6

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

Found valid GPT with protective MBR; using GPT.
Disk /dev/sda: 58626288 sectors, 28.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 63EE03DD-4F8F-49C5-9564-56179029BD32
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 58626254
Partitions will be aligned on 2048-sector boundaries
Total free space is 23584941 sectors (11.2 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          206847   100.0 MiB   EF00  EFI System Partition
   2          206848         8402943   3.9 GiB     FD00
   3         8402944        10450943   1000.0 MiB  FD00
   4        10450944        35043327   11.7 GiB    FD00

 

# gdisk -l /dev/sdb
GPT fdisk (gdisk) version 0.8.6

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

Found valid GPT with protective MBR; using GPT.
Disk /dev/sdb: 58626288 sectors, 28.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 92063063-2A9C-4D91-888A-3FDD49CEA0D7
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 58626254
Partitions will be aligned on 2048-sector boundaries
Total free space is 23584941 sectors (11.2 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          206847   100.0 MiB   EF00  EFI System Partition
   2          206848         8402943   3.9 GiB     FD00  /boot
   3         8402944        10450943   1000.0 MiB  FD00  swap
   4        10450944        35043327   11.7 GiB    FD00  /
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