[lug] Using Loopback for /boot?

Lee Woodworth blug-mail at duboulder.com
Wed Oct 23 22:21:36 MDT 2013


On 10/23/2013 12:56 PM, stimits at comcast.net wrote:
> Actually, I forgot to add one option, as per the thread title...I was also considering if I could create a loopback mounted file from the existing /boot. E.G., create a file and format it under loopback, then use that during the install...the file would be on the original /boot, and act something like a jail to prevent interacting with other files. Not sure if during install there would be that kind of ability to name a loopback file as a /boot install, although I could create the file before install.

Another option might be just to build the new system on an external USB disk.

I just completed this procedure on a laptop:

1) install replacement SATA disk in an external USB enclosure
2) boot using existing main disk
3) partition/lvm-init/format/mount the usb disk
4) install new os version on usb disk
5) manually install grub on new usb disk (this is grub 0.97)
6) swap disks usb<->in-case sata
7) reboot
8) copy data files from old install

This was done using gentoo. I suspect you could do similar with fedora.

>
> As for a new separate partition, all current partitions are what I have. I do not use lvm, and repartitioning a partition in the middle of the others without touching those surrounding it is a possibility, but this too worries me. Simply making a new partition if there were space at the end of the drive would not be an issue, and due to losing data before manipulating a partition in the middle worries me when I can't afford to lose anything.
>
> But...making an install to a new subdirectory of the existing /boot seems to be perfect. However, I'm wondering if this is compatible with chain loading...it's been years since I messed with such boot details, but I am thinking there may be requirements of where files are placed in /boot relative to PBR. The motherboard is about 4 years old, so I'm assuming this is not likely an issue.
>
> I should state that my real question is "what are the safe ways of using the existing /boot *partition* and grub2 to not risk the existing linux install and existing windows 7 install". I'm very weary of any downtime, or any install method which could prove risky to any data. What are the risks of manipulating a non-lvm unused partition in the middle of the disk? What are the risks of installing a second fedora using the exact same /boot?
>
> The web link you gave does inspire me to simply install everything on one partition...it claims:
>     This is a holdover from "ye olde tymes"
> ...how many people here no longer use a separate /boot? Alternately, if I installed everything to a single root partition, and then eventually satisfied myself that all things are copied over and I was willing to destroy the old f16 and its /boot, how hard is it to migrate from one /boot directory on the root partition to a separate /boot partition (thus overwriting the old f16 /boot)?
>
> I guess the ideal situation would be that a separate /boot partition really does no longer have any meaning or advantage.
>
> ----- Original Message -----
> From: Davide Del Vento
> To: Boulder (Colorado) Linux Users Group -- General Mailing List
> Sent: Wed, 23 Oct 2013 18:30:30 -0000 (UTC)
> Subject: Re: [lug] Using Loopback for /boot?
>
> Why do you want to *share* boot?
> If I were you in your shoes I'd just make another *separate* boot partition (mounted as /boot in F19 and something like /f19boot in F16) and use that instead. Or even do not make a /boot partition at all, of course this has pros and cons as you probably know http://unix.stackexchange.com/questions/256/is-it-good-to-make-a-separate-partition-for-boot
>
>
>
>
> On Wed, Oct 23, 2013 at 12:15 PM,  <stimits at comcast.net> wrote:
>
>
> Hi,
>
> I have an older machine with hardware issues on SATA ports which means the two disks I have now are the only disks I can attach. I'm interested in installing a newer version of fedora 19 (it has an existing fedora 16 install) to a spare 300 GB partition. The trick is that I have only one /boot, and I do not want to harm the older install until I'm sure everything is up and running on the newer install. The /boot/grub2/ is what worries me.
>
>
>
> Current layout is no lvm used (just ordinary partitions). Drives: first SATA drive contains windows 7 and linux swap (sda), while the second hard drive contains fedora 16 and /boot (sdb). Second drive also contains the spare 300 GB partition (sdb), currently formatted ext4. My desire is to install fedora 19 to the spare sdb, share the /boot and swap, and either edit the existing grub boot from old fedora 16, or replace it with the new fedora 19 grub boot, with windows 7 and all linux installs remaining bootable with no down time. FYI, without everything remaining on the existing drive, I cannot add a new drive without replacing the motherboard.
>
>
>
> I suspect I can simply install fedora 19 and tell it to not format /boot, then tell it to install on MBR of sda, or possibly even tell it to not even install boot to MBR, but instead edit the grub boot menu. Kernels themselves would not be overwritten due to version naming, but I still worry about grub issues. Can anyone give me advice on how dangerous this scheme is to damaging any of the existing operating systems? Or insights on using a single /boot for two fedora installs? I'm trying to avoid putting /boot on the same partition as / for the new install, but perhaps this would be the only way.
>
>
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