mugglewei / bdchecker

backup data checker

• readme 中文
• readme EN

Overview

bdchecker (Backup Data Checker) is a tool for checking personal cold backup data, helping you discover data corruption in time

Why use it

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

1. Use hard drives from different production batches for multiple backups
2. Regularly check whether files are corupted
3. 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

Install

• use pip

pip install bdchecker

• download from project's Releases, and decompress

Usage

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.meta folder.
• 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)

Example directory

Assume that we currently have the following directory structure

data
├──── a.txt
├──── b.txt
└──── c
      ├──── c1.txt
      └──── c2.txt

Command: gen

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.

Command: clean

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.

Command: check

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.

Migration and comparison

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.