Convert to raid 1 CentOS 7

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The Need

I recently had the need to convert my home server setup from single disk to raid 1 without loosing data or reinstall the system. I found various articles around for this but mostly for old version of redhat/centos, debian/ubuntu and older initramfs/grub version. For personal reference and to thank all the people that share information i'm writing this article.

Main reason for this headache: have a more safe place to store some important data and, since I use mostly really cheap or "cost zero" hardware, a safer place for my CentOS 7 installation.

I'm no expert, follow this instruction at your own risk. I'm not responsible for data loss, or any damage that might occur following this instructions. It just worked for me.

Backup all your data

Remember that raid 1 is not a backup, always do your backups!!!


This is a really small wiki for personal use, no talk/discuss or user registration is allowed.

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fell free to contact me for any info, comments, personal experience or correction to this page

"cmatthew" [dot] "net" [at] "gmail" [dot] "com"


Current setup

1x segate barracuda 500gb as /dev/sda with 3 partitions.

/dev/sda1 /boot
/dev/sda2 swap
/dev/sda3 /

Current partitions are XFS not using LVM

What we need

I'm adding a second identical disk /dev/sdb for raid 1 setup. The raid will be a linux software raid managed by "mdadm" be sure to have package installed.

yum install mdadm

Be also sure to have a lot of patience, junk food and caffeine as usual :)


A full working backup of everything.

New disk

Plug in new disk

/dev/sdb pretty obvious.


Create identical partition scheme as curent disk /dev/sda

sfdisk -d /dev/sda | sfdisk /dev/sdb


fdisk -l

Convert new disk /dev/sdb partitions to "Linux raid autodetect"

fdisk /dev/sdb use "t" to convert all 3 partitions to "fd"


fdisk -l

Create degraded raid 1

Create for all partition on new disk /dev/sdb

mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-devices=2 missing /dev/sdb2
mdadm --create /dev/md2 --level=1 --raid-devices=2 missing /dev/sdb3


cat /proc/mdstat

Create filesystem raid 1

Create for all newly created raid 1 partition

mkfs.xfs /dev/md0
mkswap /dev/md1
mkfs.xfs /dev/md2

Transfer data


Mount both / and /boot

mount /dev/md2 /mnt/
mount /dev/md0 /mnt/boot/

Copy existing data

rsync -auxHAXSv --exclude=/dev/* --exclude=/proc/* --exclude=/sys/* --exclude=/tmp/* --exclude=/mnt/*  /* /mnt
rsync -auxHAXSv /boot/* /mnt

I'm no rsync expert this did the job for me.

Grub2 and initramfs

Mount system information

Mount both / and /boot (should be already mounted)

mount /dev/md2 /mnt/
mount /dev/md0 /mnt/boot/

System information

mount --bind /proc /mnt/proc
mount --bind /dev /mnt/dev
mount --bind /sys /mnt/sys
mount --bind /run /mnt/run


Jail! No harm to current system.

chroot /mnt/


Edit fstab with new dirve UUID information

blkid /dev/md*
/dev/md0: UUID="your-UUID" TYPE="xfs" 
/dev/md1: UUID="your-UUID" TYPE="swap" 
/dev/md2: UUID="your-UUID" TYPE="xfs"
vim /etc/fstab 
UUID=your-UUID /                       xfs     defaults        0 0
UUID=your-UUID /boot                   xfs     defaults        0 0
UUID=your-UUID swap                    swap    defaults        0 0

Create mdadm configuration

mdadm --detail --scan > /etc/mdadm.conf


Backup current and create new initramfs

cp /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.bck
dracut --mdadmconf --fstab --add="mdraid" --filesystems "xfs ext4 ext3 tmpfs devpts sysfs proc" --add-drivers="raid1" --force /boot/initramfs-$(uname -r).img $(uname -r) -M

Grub parameters

Add some default parameters to grub

vim /etc/default/grub
GRUB_CMDLINE_LINUX=" rhgb quiet"

Make new grub config

grub2-mkconfig -o /boot/grub2/grub.cfg

Install grub

Install grub on new disk /dev/sdb

grub2-install /dev/sdb


At this point you can reboot the system choosing new disk /dev/sdb from bios, or plug old disk /dev/sda out. if all worked out system will boot, check mount points and raid status

swapon -s
Filename                                Type            Size    Used    Priority
/dev/md1                                partition       12279804        0       -1
mount -t xfs
/dev/md2 on / type xfs (rw,relatime,attr2,inode64,noquota)
/dev/md0 on /boot type xfs (rw,relatime,attr2,inode64,noquota)
cat /proc/mdstat

Or if didn't work out.. well we didn't touch any data or anything else on original disk so read more, start over.. don't complaint u'r use to it :)

Add old disk to array

Now we ca add old disk /dev/sda to the array. Change partition type to "Linux raid autodetect".

fdisk /dev/sda use "t" to convert all 3 partitions to "fd"

Add disk to raid 1 array

mdadm --manage /dev/md0 --add /dev/sda1
mdadm --manage /dev/md1 --add /dev/sda2
mdadm --manage /dev/md2 --add /dev/sda3

Check rebuild

watch -n1 "cat /proc/mdstat"

Reinstall grub on /dev/sda

grub2-install /dev/sda


add to /etc/mdadm.conf

vim /etc/mdadm.conf


The status of raid device will be checked once a week by default

cat /etc/cron.d/raid-check
# Run system wide raid-check once a week on Sunday at 1am by default
0 1 * * Sun root /usr/sbin/raid-check

to change parameters check /etc/sysconfig/raid-check


Use smart features if available on hard drives

yum install smartmontools

This is my personal configuration: comment all lines in /etc/smartmontools/smartd.conf and add

/dev/sda -H -C 0 -U 0 -m root
/dev/sda -a -o on -S on -s (S/../.././02|L/../../1/04)
/dev/sdb -H -C 0 -U 0 -m root
/dev/sdb -a -o on -S on -s (S/../.././02|L/../../1/04)