Checkitgui is a file integrity tool for Linux and Unix systems.

Checkitgui Copyright (C) 2014 Dennis Katsonis

LICENCE INFO

Checkitgui is free software distributed under the GNU GPL. See below for copyright for CRC64.

WHAT THIS PROGRAM DOES:

Checksum adds additions data assurance capabilities to filesystems which support extended attributes. Checkitgui allows you to detect any otherwise undetected data integrity issues or file changes to any file. By storing a checksum as an extended attribute, checkitgui provides an easy way to detect any silent data corruption, bit rot or otherwise modified error.

This was inspired by the checksumming that is performed by filesystems like BTRFS and ZFS. These filesystems ensure data integrity by storing a checksum (CRC) of data and checking read data against the checksum. With mirroring of data, they can silently heal the data should an error be found.

This program does not duplicate this ability, but offers rudimentary checksum abilities for other filesystems. It simply calculates a checksum and stores the checksum with the file. It can then be later used to verify the checksum against the data. Any data corruption of file changes would result in a failed check.

Checkitgui is a graphical version of checkit. You do not need checkit installed to run checkitgui.

WHY IT WAS CREATED:

Moving data from disk to disk, or leaving data on the disk, leaves a very small possibility of silent data corruption. While rare, the large amounts of data being handled by drives make silent corruption a real possibility. While BTRFS and ZFS can handle this, other filesystems can’t. This program was created to add an ability to detect (but not fix) issues. With the ability to detect, you can easily find out whether a copy or extract operation occured perfectly, or whether there has been bit rot in the file.

Backups provide point of reference, but comparison isn’t very efficient, as it involves reading two files. Using a CRC, you only need to read the file once, even after a copy operation to determine whether the file is OK. Also, should the file be different from the backup, which copy is OK, the backup or the original? Checkitgui will let you know whether it is the backup or original which has changed.

There are other ways to do this. You can use a cryptographic hash and store a SHA-1 or MD5 or SHA-256 value in a seperate file, or even use GPG and digitally sign the file. The problem is, that the value is stored in a seperate file, and doing directory recursion, or all files of a particular type (i.e., all JPG’s isn’t as straighforward. With checkitgui, the CRC is stored as an extended attribute. It remains as part of the file, and can be copied or archived automatically with the file. No need for seperate files to store the hash/checksum.

Checkitgui also has the ability to export this to a hidden file, and import it back into an extended attribute.

DOWNLOAD:

Here is the source code , which you can compile. GPG signature for the above source package. Signing key: D78BA4DD4AADF348

There are also ready to use packages for Fedora and RPM based distros

RPM for Fedora and RedHat Distros (64 bit)

RPM for Fedora and RedHat Distros (32 bit)

SRPM

Debian package for 64 bit systems

Debian package for 32 bit systems

Debian source files here

HOW TO USE:

Checkitgui calculates and stores the CRC as an extended attribute (user.crc64) or as a hidden file. The file must reside on a filesystem which supports extended attributes (XFS, JFS, EXT2, EXT3, EXT4, BTRFS, ReiserFS among others) to use the extended attribute (recommended).

First, run checkitgui to store the CRC as an attribute, then at any time, you can run checkitgui to check that the file data still matches the CRC. If any of the files don’t match, or the CRC is missing, checkitgui will report it. If you pass the “verbose” option, checkitgui will summarise the files that didn’t pass the checksum test at the end of the run.

OPERATION:

Use “Add File” or “Add Directory” to add a single file, or an entire directory tree. The files will be displayed in the main windows.

“Check” will check the files against the CRC. At the completion, the files will be green with “PASSED” if they pass, and red with “FAILED” if not. Passed means that the file data read matches exactly the file data when the checksum was created. Failed means that the data read does not match either due to the file being modified, or possibly disk error or faulty media.

Click “Store” to calculate the CRC and store it alongside the file. By default, if the file already has a CRC, it will not be overwritten unless the “Overwrite” checkbox is checked.

“Clear” clears the list of files.

Right clicking on a file in the list brings up a context menu. Here you can

“Export” the CRC to a file. This will be a hidden file called .filename.crc64

The file will have the hidden attribute set for FAT32 and NTFS filesystem, be prefixed with a ‘.’ and suffixed with .crc64

Use this to save the attribute to a separate file if moving the file to a filsystem which doesn’t support extended attributes (such as FAT32 or ISO for CD/DVD archives.

“Import” the CRC from a file. The hidden file exported using the “Export” function above will be imported into the file as an extended attribute.

Use this to bring the exported CRC back as an extended attribute when moving the files from a filesystem which does not support extended attributes to one which does.

“Allow CRC Overwrite” Toggling this will determine whether the existing CRC can be overwritten with a new recaculated value. By default, this is disabled, but in cases where you expect to modify the file, you may want to enable this to allow you to recalculate the new CRC.

“Result Log” allows you to view categorised results. This will provide a clearer picture of which files passed and failed, and why. You can save the log to a HTML formatted file.

LIMITATIONS:

As checkitgui doesn’t repair files, you need to ensure that you have backups of important data. Checkitgui by default stores the CRC in an extended attribute.

If the checksum is stored as an extended attribute, which is the default, it will be lost if you transfer the file to a filesystem which does not support extended attributes, or the method of copying does not preserve them. If you export the CRC, then the CRC can travel with the file as long as you copy the CRC hidden file as well.

Checkitgui cannot detect changes and recompute the checksum without being run manually, because it doesn’t run in the background. While having a ‘checkit’ daemon, which can automatically update the checksum should the file be changed is potentially useful, this is better done by migrating to BTRFS or ZFS, which handles this more efficiently than checkitgui ever could.

TODO:

• Intergration with file managers.

CRC64 routine.

The checksum routine is the crc-64-jones created by Salvatore Sanfilippo.

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