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Is it possible to switch to running Linux from RAM or RAM disk after starting starting initially from disk?

eg. You need to make an image of your hard disk, FTP it to a remote location, some time later you want the image back, so you start the system from disk as usual, restore the image you FTP'd from the remote location back into place.

More like a CloneZilla backup and restore, without booting the server from CD or USB disk, but starting from the normal hard disk?

Notes on environment I should have mentioned it earlier. It is a remotely hosted VM where I cannot boot into a recovery console mode or do a netinstall. It will always boot onto the same disk. Which means that if there is some serious corruption I can't repair it offline, which is why being able to ftp a previously saved backup into place is so important

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Are you doing the initial setup of this system? Have you considered setting up LVM and leaving free space in you VG? With LVM it should be pretty easy to at any point in the time to create a new logical volume, copy a working filesystem to it, and adjust your bootloader to use the new LV as root. –  Zoredache Nov 17 '10 at 21:19
    
I am not doing the setup myself. It is a VPS hosting provider who have not yet implemented a proper backup or a rescue mode system. It is more or less in a beta state. The disk creation and the booting is totally outside my control. I can only read and write to the disk. There are some suggestions here about pivot_root and kexec I am not familiar with. My idea is to switch root to some NFS system in the same datacentre and follow the kexec or pivot root options from there. –  vfclists Nov 17 '10 at 21:41

3 Answers 3

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If you really need to do this without restarting, you're looking for pivot_root.

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Its called PXE booting,network booting or diskless booting..

Its great to run servers without disks... Is this what you want to do?

if you pull down a PXE image, you can basically do anything :D

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You could do this in a number of ways. You could just completely netboot, as Arenstar suggests. Or, you could boot into a normal environment, transfer the new one into to place, and use kexec to start it.

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