With Fedora-Live-Desktop-x86_64-19-1 installed to a vfat formatted Live USB device, I find this report in /var/log/messages on each reboot:
Aug 8 17:24:09 localhost kernel: [ 8.255350] FAT-fs (sdc1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
Aug 8 17:24:09 localhost kernel: [ 11.052845] bio: create slab <bio-1> at 1
Aug 8 17:24:09 localhost kernel: [ 11.179108] EXT4-fs (dm-0): mounted filesystem with ordered data mode. Opts: (null)
Once unmounted, fsck reports that the dirty bit is set:
[root@localhost ~]# fsck.vfat -rv /dev/sdc1
fsck.fat 3.0.22 (2013-07-19)
fsck.fat 3.0.22 (2013-07-19)
Checking we can access the last sector of the filesystem
0x41: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt.
1) Remove dirty bit
2) No action
? 1
Boot sector contents:
System ID "SYSLINUX"
Media byte 0xf8 (hard disk)
512 bytes per logical sector
4096 bytes per cluster
32 reserved sectors
First FAT starts at byte 16384 (sector 32)
2 FATs, 32 bit entries
7798784 bytes per FAT (= 15232 sectors)
Root directory start at cluster 2 (arbitrary size)
Data area starts at byte 15613952 (sector 30496)
1948715 data clusters (7981936640 bytes)
62 sectors/track, 247 heads
0 hidden sectors
15620218 sectors total
Checking for unused clusters.
Checking free cluster summary.
Perform changes ? (y/n) y
/dev/sdc1: 18 files, 644955/1948715 clusters
I wonder if this may be due to a Bash shell not getting properly shut down during shutdown, as reported here,
http://lists.freedesktop.org/archives/systemd-devel/2013-July/012307.html
--Fred