Messages in this thread | | | From | "H. Peter Anvin" <> | Subject | Re: klibc | Date | Fri, 9 Jun 2006 15:48:43 -0700 (PDT) |
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Followup to: <bda6d13a0606091528h4e85265du8651818c73827b7d@mail.gmail.com> By author: "Joshua Hudson" <joshudson@gmail.com> In newsgroup: linux.dev.kernel > > Once again. Loopback mount requires a clean unmount of root and > host filesystem. After remounting root read-only, host is still read-write > and cannot be remounted read-only. > > It is necessary to provide access to the rootfs tree somewhere else > or use pivot_root, like the initrd solution below: > > initrd: /linuxrc > #!/bin/sh > mount /dev/hda1 -o rw -t ntfs /host > mount /host/linux/root.img -o loop,ro -t ext3 /root > pivot_root /root /root/initrd > exec /initrd/bin/init > > root:/etc/rc.d/rc.halt: > #!/bin/sh > pivot_root /initrd /initrd/root > cd / > exec /stop $RUNLEVEL > > initrd:/stop > #!/bin/sh > kill -SIGUSR1 1 > umount /root > umount /host > case $1 in > 0) poweroff -f ;; > *) reboot -f ;; > esac > > This requires static binaries of init, sh, mount, umount, an extant /etc, and a > few nodes in /dev.
Another solution is to leave a process with its cwd parked in the rootfs. Look at run_linuxrc() in usr/kinit/initrd.c of any klibc tree to see how this can be used. (That is there to support old-style /linuxrc, but should be applicable here, too.)
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