What is rootfs?

I'm a longtime Fedora user and I've just installed FC15. The new partition layout is confusing to me, as I'm used to the "plain vanilla" partitions that previous versions used.

[root@localhost ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
rootfs                7.9G  596M  6.9G   8% /
udev                  496M     0  496M   0% /dev
tmpfs                 502M     0  502M   0% /dev/shm
tmpfs                 502M  288K  501M   1% /run
/dev/mapper/vg00-lv00
                      7.9G  596M  6.9G   8% /
tmpfs                 502M     0  502M   0% /sys/fs/cgroup
tmpfs                 502M     0  502M   0% /media
/dev/sda1             194M   20M  165M  11% /boot
/dev/mapper/vg00-lv03
                      2.0G  312M  1.6G  17% /var
/dev/mapper/vg00-lv02
                       20G  172M   19G   1% /home

I understand that the tmpfs partitions are mounted from an internal RAM disk. But what is this new rootfs partition and why does it appear to be mounting / twice?

Solution 1:

rootfs is a special tempfs image used in initram, and stays in this instance because you have an encrypted LVM setup. Normally, init would overwrite rootfs with the actual mounted / file system, but Fedora may not have that fixed with your setup. There is no harm in it.

see: http://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt

Solution 2:

I think this is a side-effect of symlinking /etc/mtab to /proc/mounts as this forum post suggests.