[CentOS] Upgrade from CentOS6.6 to CentOS 7

Tue Dec 15 19:14:30 UTC 2015
m.roth at 5-cent.us <m.roth at 5-cent.us>

Digimer wrote:
> On 15/12/15 11:10 AM, m.roth at 5-cent.us wrote:
>> Traiano Welcome wrote:
>>> On Tue, Dec 15, 2015 at 6:36 PM, Digimer <lists at alteeve.ca> wrote:
>>>> On 15/12/15 10:17 AM, Traiano Welcome wrote:
>>>>> Is it possible to upgrade from CentOS 6.7 to CentOS 7?
>> <snip>
>>>> Given how radically the OS changed, I would strongly advice against
>>>> it.
>>>> The move from sysvinit to systemd alone is enough to recommend against
>>>> an upgrade.
>>> So it's not possible under any circumstances?
>> Let me offer you one option: *IF* you have enough space on your
>> filesystems, you could:
>> mkdir /boot/old /old
>> zsh
>> zmodload zsh/files
>> mv /boot/* /boot/old/
>> mv /usr  /old/
>> mv /lib* /old/
>> sync
>> sync
>> And go into the installer. If you have a problem, you can go back....
> How would the move from the old to new grub work, particularly in
> reverse if needed?

Was just reading Alice's post, and it struck me a safe way would be for
the o/p to do a clean install on a different machine, then do the rsync's
I mention.

Several gotchas: don't forget to copy the old /etc/ssh/ssh_host* to the
new /etc/ssh/, check the ifcfg-<NIC>, /etc/udev/rules.d/, and, if the new
system is different hardware, rebuild the initrd *before* you reboot. You
can also edit /boot/device/grub whatever the damn grub2 thing is, also
before reboot.

Or edit on the boot, get it up, and rerun grub2-install.