I asked this in Vol 154, Issue 29:
    I've a system that has been running CentOS 6 64-bit for almost
    4-years and I want to start the move to CentOS 7 64-bit.
    I run software RAID-1 with LVM everywhere except /boot which is a
    standard partition RAID-1.
    There are 2 areas that concern me greatly about this migration:
    1. How do I duplicate my current grub configuration file that
    supports a failure of /dev/sda to grub2?
    2. How do I install CentOS 7 but use my existing hard drive layout
    so I only format specific OS file systems. My drive layout goes back
    to the original proposed FHS layout. The separate partitions related
    to the operating system are:
        /boot??????? 1GB? (standard boot as defined in fstab is /dev/md0)
    The following file systems are all defined in volume group
    vg_jpdopsys (size is 64 GB)
        / (root)????? 6GB
        /home?????? 4GB
        /opt?????????? 4GB
        /tmp????????? 2GB
        /usr??????????? 12GB
        /usr/local? 2GB
        /var??????????? 8GB
    The following file system is defined in volume group vg_jpdswap
    (size is 24 GB)
        swap????????? 16GB
    Plus many other file system dedicated to specific applications and
    data all using logical volume management.
    When I moved from CentOS 5 to CentOS 6 all of the OS partitions were
    formatted except /home.? All went extremely well then.
    But I don't see a way to do that with CentOS 7 retaining the
    existing disk configuration.
    Is there some detailed installation instructions showing some
    advanced methods?
    TIA
    Gene
If you saw the original post you will see that I did clean it up a bit.? 
I'm starting this move now understanding that I have until 2020 to do it.
Any suggestions?
TIA
Gene
-- 
Eugene Poole
Woodstock, Georgia