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Saving Your Ass(ets) with chroot. Alan Bailward <alan@ufies.org> April 15, 2004 For the Fraser Valley Linux Users Group. What is chroot?. Allows running of commands with an arbitrary root directory Syntax: chroot NEWROOT [command] Used to “jail” applications
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Saving Your Ass(ets) with chroot • Alan Bailward <alan@ufies.org> • April 15, 2004 • For the Fraser Valley Linux Users Group
What is chroot? • Allows running of commands with an arbitrary root directory • Syntax: chroot NEWROOT [command] • Used to “jail” applications • Mostly used for security applications • i.e.: servers
Getting in Trouble • Easy to have Linux problems • Errors on install • Broken kernel • Broken lilo • Normally you’re out of luck, to a degree, or need to deal with accessing things from a BootCD
Getting Out of Trouble • The old way
The Old way • Get to your system • Floppy • BootCD • Fix it • Mess with lilo/lilo.conf • Compile kernel, hope it works
Getting Out of Trouble • The New Way
Using chroot • Lets you access your system as it was • Full access to accurate /proc and /dev • No funky pathing • Easy to jump in and out of
How To Use chroot 1 • Boot with BootCD • mkdir /mnt/new • mount /dev/hda1 /mnt/new • mount /dev/hda2 /mnt/new/boot • mount /dev/hda3 /mnt/new/var
How To Use chroot 2 • mount -o bind /proc /mnt/new/proc/ • link the “real” /proc into your new file structure • mount -o bind /dev /mnt/new/dev/ • ditto for /dev (only for devfs systems)
How To Use chroot 3 • cp /etc/resolv.conf /mnt/new/etc/ • need accurate network info • chroot /mnt/new /bin/bash • enter the system • env-update # gentoo only • update environment settings
How To Use chroot 4 • You are now in a shell that is your old system • cd / puts you in your old / (really /mnt/new/) • Can run lilo, compile kernels, etc • To exit, type ‘exit’ to exit, then unmount disks and reboot