Overview

HTTPS SSH
NAME

fscheck
a module for Python

ABOUT THIS PROGRAM

A consistency check for checking what files were made unavailable by bad
sectors.

Say you have a disk with bad sectors, you copy the partitions off it using
gddrescue. You don't know what files were broken or made unavailable by
directory inodes becoming corrupt. This program scans the directories,
starting with an initial set (for example the root directory or a list of
specific directories) and recurs into them, checking for errors. It does
not list erroneous files.

This program is used as a Python module which you import into the
interpreter.  You instantiate the FSCheck class and feed it a gddrescue
log. It uses debugfs (the ext3 filesystem debugger interpreter, not the
kernel debugging tool) through a fairly finicky but surprisingly solid
pexpect integration. There is no python interface for any debugfs-like
functionality, alas.

It's fairly conservative with resources, even with 30k files scanned
the Python interpreter running it takes no more than 50 megabytes memory.

USAGE

You can either write a wrapper program around the fscheck module, or you
can use it from the interpreter. Either way, you need to be running the
python interpreter as root. The general operation will look like so:

>>> import fscheck
>>> B = fscheck.BadBlocks(file('gddrescue.log'))
>>> C = fscheck.FSCheck(B, '/dev/sdf1')
>>> ' '.join(map(lambda x: x[1], C.dispatch.workers[0].ls((None, '/'))))
# ^ this is not supported, but works for now
'. .. lost+found var etc media cdrom' # and so on
>>> C.start_check([(None, '/opt')]) # check /opt and all subdirs
^C # Interrupt at any time
>>> C.paths
[ ... paths queued for checking ... ]
>>> print C.dispatch.workers[0].cmd('stat "/"') # also not supported. 
					# gets output from debugfs.
>>> C.continue_check()

You can also interrupt start_check with Ctrl-C and then continue using
continue_check which you can again interrupt. You might want to do that
to check the state of the process, for example see what paths are queued
up for being checked or what files have been found to have errors in them.

If you want to dig deeper you can use the FSCheck.perform_check method
which is a coroutine/generator that yields control after each file
that it tests. The generator can be suspended at any time with Ctrl-C,
it doesn't lose track of the file being processed at the moment.

Finally, you can use the DebugFSDispatcher class as a direct Python
interface into ext3 debugfs. It's relatively slow but better than
nothing! The cmd method returns text, which you have to parse yourself. The
text put out by debugfs is usually easy to parse. It is useful to make
note of the amount of spaces between different output columns.

You can also use BadBlocks as a python interface/parser for gddrescue logs.
It cannot write out new gddrescue format logs but thanks to the format
it is super easy to do.

LICENSE

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.