bdchecker (Backup Data Checker) is a tool for checking personal cold backup data, helping you discover data corruption in time
Imagine that we have some data that needs to be cold backup, which may be the raw market data of a certain financial market that is compressed every day; or some electronic versions of classic movies owned by individuals; or some keys that are not used all year round; Let’s first list some options:
| Storage plan | Storage life span |
|---|---|
| SSD | several years to more than ten years |
| HDD | 10+ years |
| tape drive | 30+ years |
| punched paper | thousand of years |
| Carved in stone (Luo Ji raised his crutch above his head and shouted solemnly) | millions of years |
There is no doubt that if you have enough financial resources to engrave the information on stone and store it properly, it should be very safe unless you are attacked by a dual-vector foil attack; but for individuals, the cost of reading information from stones should be far greater than the value of the data we need to save.
So when considering the ease of reading and writing of data, it is obvious that the hard disk is the most convenient; but this brings additional requirements, that is, we need to regularly check whether the data is corupted.
To sum up, a simple and clear cold backup solution is
- Use hard drives from different production batches for multiple backups
- Regularly check whether files are corupted
- If corupted occurs, the remaining backup files can be used to repair it.
bdchecke is a small tool used to regularly check whether files are corupted
- use pip
pip install bdchecker
- download from project's Releases, and decompress
bdchecker include 3 sub-command
- gen: scan directory, recursively traverse to generate the hash information of all new files in the directory, and place them in the
.bdchecker.metafolder. - clean: scan directory, clean deleted files from hash information
- check: scan directory, Find corrupted files (note that this operation will calculate the hash value of all files, which is more time-consuming)
Assume that we currently have the following directory structure
data
├──── a.txt
├──── b.txt
└──── c
├──── c1.txt
└──── c2.txt
Generate hash infos
bdchecker gen -d data -v 1
-d: directory for which information needs to be generated-v: verbose level
After missiong completed, you can see console output: dump meta info to data/.bdchecker.meta/sha256.csv
When there are no new files in the directory, repeatedly executing the gen command will not actually generate the hash information of the file.
remove data/c/c2.txt, then run
bdchecker clean -d data -v 1
You can see in the last few lines of the log: clean missing file's meta info: c/c2.txt, which means that we have successfully cleaned the hash information corresponding to the file.
run
bdchecker check -d data -v 1
The last line of the log appears: all check pass, which means there are no new/deleted files and all files are not corrupted.
Now, let's modify a.text, write something randomly, and then run again
bdchecker check -d data -v 1
At this time, an error message appears in the log: check failed: a.txt, old hash: ..., cur hash: ..., indicating that the content of a.txt has changed.
The hash information generated by bdchecker will be saved in the .bdchecker.meta in the directory, so you can directly migrate the entire folder during migration.
When there are already multiple backup data and no hash value has been generated; at this time, you can use the bdchecker gen command to generate a hash value for each backup data, and then compare the two files. Since the generated file lines are already sorted, so you can directly use commands such as diff for comparison.