I Chris,

you were really good in your explanation which helped me a lot to understand ..

Thank you for your time and your patience ...

Angelo

On Sun, Feb 1, 2015 at 8:57 PM, Chris Murphy <lists@colorremedies.com> wrote:
On Sun, Feb 1, 2015 at 10:16 AM, Angelo Moreschini
<mrangelo.fedora@gmail.com> wrote:
> <  No. Syslinux is a bootloader. Its job is to find, load, and execute a
> <  kernel.
>
> Ok  now I understand better...
> So syslinux need to know what is the kernel that have to be installed...

Yes. Except, loaded rather than installed; loaded suggests read from
disk into memory, installed suggests extracted from package and saved
to a drive.

syslinux - isolinux - extlinux all typically look to a configuration
file for this. The configuration file includes drawing a menu, what
the menu options are, and their underlying commands. Or you can do it
from the boot: prompt. All of this is fairly well detailed in syslinux
documentation.

>
> <  I'm uncertain what you mean by "virtual kernel"
>
> I mean the kernel that is running on the computer (I used 'virtual'
> inappropriately, because it is loaded from a special support - the CD used
> for the procedure of  restoring - and not is loaded from the HD that is
> installed on the computer).

Well if you're booting from other media, then first you need to
identify the partition that contains the file system volume you want
to repair. Some combination of:

parted -l
lsblk
blkid

Should hopefully give you a hint what /dev/sdXY is that partition. And
then it depends on what filesystem it is what command you should use:
e2fsck, xfs_repair, btrfs check, and so on. fsck itself will detect
the file system and run fsck.<foo> but off hand the only three
filesystems this works on are ext234, fat, and ntfs.

But like I mentioned in another thread, it's easier to just use
rd.break=cmdline as a kernel parameter from the boot menu of the
installed system (no rescue media), and then just do file system
check/repair from there. Both the hostonly (default) and nohostonly
initramfs contain disk repair tools. So you don't need a successfully
mounted root to have access to these tools. And further, except for
FAT, it's not that common to need fsck. All the other filesystems
listed have journals and usually journal playback is sufficient to
make the file system consistent again. The whole idea of journals is
to obviate the need for (most, not all) filesystem checks or repairs.
So if you have to do it often it'l make me think something else is
wrong that's causing file system corruption to happen.



--
Chris Murphy
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