On 2009-03-25 18:50, Paul E Condon wrote:
Top post because it is OT, but related. Yesterday I had occasion to
remove some old data from my system. I had a backup copy, and the data
was all on a single partition. I could have simply rewritten the file
system with mke2fs, but I decided, instead, to use rm -rf * at the top
level of the file structure. There were about 25million files on an
7 GB partition on a 60 GB IDE drive. It took rm a little over an hour
to unlink it all.
(Yes, I know that unlinking doesn't get rid of the data. I wiped it
because I didn't want to leave it in place and forget that it is the
old data of which I have a perfectly good archival copy. Not security,
but good housekeeping.)
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html
After reading Gutmann's epilogues of his 1996 paper, I wrote a
simple freespace wiper that runs a lot faster than sfill from
secure-delete.
$ cat /home/me/sfill.py
#!/usr/bin/python
import sys, statvfs, os
import time
import traceback
import math
__buff = ''
def write_buff(f, buff_size):
global __buff
stats = os.statvfs(loc)
free_bytes = stats[statvfs.F_BSIZE] * stats[statvfs.F_BFREE]
if free_bytes < buff_size:
__buff = chr(0xFF) * free_bytes
try:
f.write(__buff)
f.flush()
except:
print 'write error'
traceback.print_exc(file=sys.stdout)
sys.exit()
return free_bytes - buff_size
try:
loc = sys.argv[1]
except:
print 'need a mount point!!!'
sys.exit(1)
try:
stats = os.statvfs(loc)
except:
print loc + ' is an invalid mount point'
free_bytes = stats[statvfs.F_BSIZE] * stats[statvfs.F_BFREE]
print 'free bytes = ', free_bytes
try:
buff_size = int(sys.argv[2]) * 2**20
except:
buff_size = 16 * 2**20
__buff = chr(0xFF) * buff_size
f = open(loc+'/oooooooo.ooo', 'wb')
start_tm = time.time()
start_st = time.localtime(start_tm)
print 'Starting at ', time.strftime('%Y-%m-%d %H:%M:%S', start_st)
c = 0
bytes_free = free_bytes
try:
while bytes_free >= 0:
bytes_free = write_buff(f, buff_size)
c += 1
if int(math.fmod(c, 500)) == 0:
print \
'%s %8d %16d' % \
(time.strftime('%Y-%m-%d %H:%M:%S'), \
c, free_bytes - bytes_free)
except:
print 'Terminating prematurely'
traceback.print_exc(file=sys.stdout)
f.close()
os.remove(loc+'/oooooooo.ooo')
end_tm = time.time()
end_st = time.localtime(end_tm)
print 'Stopping at ', time.strftime('%Y-%m-%d %H:%M:%S', end_st)
elapsed = end_tm - start_tm
print 'Elapsed minutes: %10.2f' % (elapsed*1.0/60,)
--
Ron Johnson, Jr.
Jefferson LA USA
"Freedom is not a license for anarchy."
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