☂︎ Optimised for high performance and low CPU usage
☂︎ Locks disks for exclusive access while cloning
☂︎ Allows access to protected files bypassing security ACL
| Argument | gfc |
|---|---|
-b -bench | Benchmark read or write, also disables hash processing |
-l -log | Use with -b or -B for benchmark write to gfc-log.txt |
-l -b | Benchmark write 0x00 to gfc-log.txt |
-l -B | Benchmark write 0xff to gfc-log.txt |
-q -quiet | Suppress messages to STDOUT, use when writing to STDOUT |
-v -verbose | Output more debug messages to STDOUT |
-md2 -md4 -md5 -sha1 | Calculate hash using: MD2 MD4 MD5 SHA1 |
-sha256 -sha384 -sha512 | Calculate hash using: SHA256 SHA384 SHA512 |
-c -compare | Compare the entire file content: by default, the program displays |
| only the first difference and exits. | |
-p -peak | Calculate peaks for 16 bit RAW audio files |
-n -normalize | Normalise level for 16 bit RAW audio files |
-t | Try to assign each thread on it's own processor |
-L -lock -dismount | Lock and dismount volumes or partitions (works only on Windows) |
| This asserts exclusive access and is important when clonning. | |
| Linux: please umount all volumes manually, before accessing | |
| a disk or partition. | |
-O -offline | Take disks offline (works only on Windows) |
| This asserts exclusive access and is important when clonning. | |
| On Linux this notifies the system to scan the disk for changes | |
| to the partition table, when the program exits. | |
-OO | Implies -O. Leave disks offline when the operation is complete: |
| It is safe to detach any offline disk as soon as the program exits. | |
| If all attached disks are offline, it is also safe to cut power to | |
| the computer. Otherwise, use the shutdown command. | |
| Warning: | |
| Since cloning creates an exact copy, a clonned disk has the same | |
| GUID as the source. It is important to never have two disks with | |
| the same GUID attached and online at the same time. Otherwise the | |
| system will change the GUID on one of the disks, which prevents | |
| any system boot volume on it from being detected. Any operating | |
| system on that disk will be left in a non-operational state, since | |
| it does not know which volume contains its files. This state can | |
| be recovered by editing the Windows registry: Boot the computer to | |
| a working installation or Windows setup. Note the drive letter of | |
the system that needs to be recovered: e.g. D: | |
Start regedit, File, Load hive: | |
D:\Windows\System32\config\SYSTEM as sys. | |
Navigate to HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices. | |
Edit \DosDevices\D:, and copy the hex data. | |
Navigate to HKEY_LOCAL_MACHINE\sys\MountedDevices. | |
Edit \DosDevices\C:, and replace the hex data with the copy from | |
| the previous step. The system should now boot correctly. | |
-Write | Copy file1 to file2. Without this, a copmpare is performed. |
-a -append | file1 is appended at the end of file2 |
-r -resume | Resume an interrupted copy. Implies -append. |
-[0-9][0-9] | Set number of buffers and page size, for example: |
-4# | Set number_of_buffers = 1 << 4 = 16 |
| Higher values minimize the effect of disk speed variation | |
-#5 | Set page_size = 2MB << 5 = 64 MB |
| When accessing two files on the same disk, a value of 5 should | |
| reduce the seek overhead and improve performance on spinning disks. | |
-P[0-9] | Set page_size = 512 << 0..9, allows setting a small page size: |
| this could be very slow, but is useful when there is physical damage | |
| to the media. Since unreadable blocks are skipped, setting this to | |
| the sector size of the disk allows as much data as possible to be | |
| recovered. Note that the default page size is 2 MB, so a deffective | |
| sector of 512 bytes would cause the entire page to be skipped. |
image.img and calculate SHA256 hash
gfc / dev/ sdb image. img- sha256# Linux gfc \\.\ PhysicalDrive0 image. img- sha256# Windows
image.img on Linux
gfc / dev/ sdb1 image. imggfc / dev/ disk/ by- path/ acpi- VMBUS: 00 - scsi- 0 : 0 : 0 : 0 image. imggfc / dev/ disk/ by- path/ acpi- VMBUS: 00 - scsi- 0 : 0 : 0 : 0 - part1 image. imggfc / dev/ disk/ by- partlabel/ gvalkov image. img
image.img on Windows
gfc \\.\ d: image. img- md5gfc \\.\ globalroot\ Device\ Harddisk0\ Partition1 image. imggfc \\.\ globalroot\ Device\ HarddiskVolume1 image. imggfc \\.\ Harddisk0Partition1 image. img
d.img.7z and calculate SHA1 hash:
Use - or con as file name to read from STDIN or write to STDOUT.
gfc / dev/ sdb1- - Write- L- sha1| 7 z a- si- m0= LZMA2- mx= 7- md= 32m- mfb= 128 d. img. 7 zgfc \\.\ d: - - Write- L- sha1| 7 z a- si- m0= LZMA2- mx= 7- md= 32m- mfb= 128 d. img. 7 z
d.img.7z and calculate SHA1 hash:
7z x- so d. img. 7 z| gfc - / dev/ sdb1- Write- L- sha1# Linux 7z x- so d. img. 7 z| gfc - \\.\ d: - Write- L- sha1# Windows
gfc file. txt: stream1- sha1# sha1 hash for stream1 in file.txt gfc image. img# creates hash of [image.img], SHA1 is the default hash algorithm gfc - b- l# benchmark write performance 0x00 to [gfc-log.txt] gfc - B- l# benchmark write performance 0xFF to [gfc-log.txt] gfc \\.\ d: - Write- L- b- l# destroy data on vol [\\.\d:] gfc src. raw dst. raw- n# performs peak level audio normalization
This tool can utilise large memory page support to improve performance.
The feature requires Windows 2003 or later, and the user must have the
Lock pages in memory priviledge, which can be set in
Local Security Policy, Local Policies, User Rights Assignment.
☂︎ Apple iOS, macOS
☂︎ FreeBSD
☂︎ Linux, OpenWRT
☂︎ Windows