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Are you using a Mac ?

Are you sure your data and your backups are all-right ?

A few commands will show you how safe your data is...

Create a disk in a file and copy some data

cd ~/Desktop
hdiutil create -size 100m -type UDIF -fs HFSXJ -volname jollystest jollystest
hdiutil attach jollystest.dmg
/dev/disk8          	GUID_partition_scheme          	
/dev/disk8s1        	Apple_HFS                      	/Volumes/jollystest
cp /sbin/* /Volumes/jollystest/
shasum /Volumes/jollystest/* >jollystest.sum
umount /Volumes/jollystest

Now create a fault by writing random data to the diskfile

dd if=/dev/random of=jollystest.dmg bs=4k seek=4000 count=1000 conv=notrunc
1000+0 records in
1000+0 records out
4096000 bytes transferred in 0.473120 secs (8657424 bytes/sec)
hdiutil attach jollystest.dmg
/dev/disk8          	GUID_partition_scheme          	
/dev/disk8s1        	Apple_HFS                      	/Volumes/jollystest
diskutil verifyVolume /dev/disk8s1
Started file system verification on disk8s1 jollystest
Checking file system
Checking Journaled HFS Plus volume
Detected a case-sensitive volume
Checking extents overflow file
Checking catalog file
Checking multi-linked files
Checking catalog hierarchy
Checking extended attributes file
Checking volume bitmap
Checking volume information
The volume jollystest appears to be OK
Finished file system verification on disk8s1 jollystest

Remember, diskutil just stated "appears to be OK"

shasum --check jollystest.sum
/Volumes/jollystest/SystemStarter: FAILED
/Volumes/jollystest/autodiskmount: OK
/Volumes/jollystest/disklabel: OK
/Volumes/jollystest/dmesg: OK
/Volumes/jollystest/dynamic_pager: OK
/Volumes/jollystest/emond: OK
/Volumes/jollystest/fibreconfig: OK
/Volumes/jollystest/fsck: FAILED
/Volumes/jollystest/fsck_cs: OK
/Volumes/jollystest/fsck_exfat: OK
/Volumes/jollystest/fsck_hfs: FAILED
/Volumes/jollystest/fsck_msdos: OK
.
.
.
/Volumes/jollystest/shutdown: OK
/Volumes/jollystest/umount: OK
shasum: WARNING: 3 of 60 computed checksums did NOT match

Do you still think everything is ok on your current disk ?

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