Bit Backup - Documentation

Structure of "Bit Backup" repository

Directory {REPODIR}/objects

SHA-256 hash is used (or an alternative hash, if supported)

objects/{??}/{?????…}

Directory {REPODIR}/pack

pack/pack-{sha-512}.pack

{sha-256}::::{length in bytes}::::{sha-256}::::{length in bytes}::::{sha-512}::::{length in bytes}::::{sha-512}::::{length in bytes}::::{sha-512}::::{length in bytes}::::::::{bytes -base}{bytes-incremental}{bytes-incremental}{bytes-incremental}{bytes-incremental}{bytes-incremental}

binary diffs

File(s) {REPODIR}/bitbackupindex.{datetime}

Content

Attribute	Example	Description
PATH	/home/robertvokac
FILE_NAME	doc.txt
TYPE	-	DIR d, REGULAR -, LINK l
LINK_TARGET	a/b/text.txt	The target is in the content of binary object
PERMISSIONS	rwxrw-r--
SUID
SGID
STICKY_BIT
EXECUTABLE	1
UID	2
GID	2
OWNER	robertvokac
GROUP	robertvokac
LAST_MOD_TIME	20220110151617999
LAST_CHANGE_TIME	20220110151617999
LAST_ACCESS_TIME	20220110151617999
SIZE	263
HASH	SHA-256:{}
ACL	aaa
IMMUTABLE	aaa
UNDELETABLE	aaa
ATTRS	aaa

Permission  Symbolic Representation Octal Representation
read    r   4
write   w   2
execute x   1
no permission   -   0

Creates local .bitbackupindex

Downloads remote .bitbackupindex – if does not exist, empty file will be returned.

Compares these indexes, uploads new blobs to object addressed system (SHA-512) – packaged to 7z archives (compression=ultra + other settings)

The most reliable way would be to make md5 hashes of all the local files you care about and store it in a file. So the file will contain a list of filenames and their md5 hashes. Store that file on your ftp server. When you want to update the files on your ftp server, download the file containing the list, compare that against all your local files, and upload the files that have changed (or are new). That way you don't have to worry about archive bits, modified date, or looking at file sizes, the use of which can never be 100% reliable.

Using file sizes isn't reliable for the obvious reason - a file could change but have the same size. I'm not a fan of using the archive bit or modified date because either of those could be confused if you backup or restore your local directory with another backup program.

File(s) {REPODIR}/bitbackupindexinfo.{datetime}

DATE=20231105
TIME=102950
VERSION=1
MESSAGE=
TAG=

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