BagIt is a file packaging format that provides a standard structure for transferring digital content between repositories or archives. It allows for arbitrary content to be safely enclosed along with metadata files describing the package. The structure includes a data subdirectory containing payload files, along with required bagit.txt and manifest files listing contents and checksums. Optional tag files can specify missing pieces to download to complete the package. The format aims to facilitate reliable content exchange and replication between institutions.

1. The BagIt file package format
John Kunze and Stephen Abrams, California Digital Library (CDL)
1. start: put your files… 2. in a directory, data Summary
Replicas for a rainy day BagIt is a file hierarchy, suitable for disk- or network-
• Need a data package format that can carry any data .pdf .mpg data/ based transfer, and maybe bag return, with just
• Suitable for disk-based and network-based transfer .xls .mpg enough structure to safely enclose a manifest,
• Main purpose is to move data from one digital library checksums, tag info, and an arbitrary payload.
or archive to another for safe-keeping 4. put tag next to data
.pdf .xls
• Not important whether the receiver provide access to
or even understand meaning of the sender’s content
manifest-md5.txt
bagit.txt Bags in action
Fig. 1. Sleeping better at data
night is more likely for the
.mpg 3. create a tag
archivist who has replicas
safely tucked away at other .pdf manifest-md5.txt Library of Congress (LC) grantees send bags
memory organizations. .xls bagit.txt • For example, bagged web crawls funded by LC are
e³°°° Bag&Tag ... sent by CDL to LC, with replica sent to San Diego
A BagIt bag directory listing Holey bags! for efficiency clarrisa~
• A BagIt bag is a special directory (or Windows folder) • A common optional tag file lists “holes” to be filled
• The directory name is your choice, but inside the top • Payload is incomplete until these files are fetched LaurelJukebox
level BagIt reserves names for required files: • File fetch.txt lists URLs for receiver to grab
• data : a subdirectory where you can put anything • Benefits include (network transfers only):
• bagit.txt : a 2-line file declaring this is a bag • No need to stage extra data copy at either end
BagIt credits and details
• manifest-md5.txt : a list of files present • Cheap parallelism from fetching URLs in batches Authors from LC and CDL: Andy Boyko, John Kunze,
Justin Littman, Liz Madden, Brian Vargas
MyFirstBag/ manifest-md5.txt
bagit.txt manifest-md5.txt Many thanks to: Stephen Abrams, Mike Ashenfelder, Scott
manifest-md5.txt Fisher, Erik Hetzner, Keith Johnson, David Loy, Tracy
| manifest-md5.txt fetch.txt bagit.txt
fetch.txt Seneca, Mark Phillips, Adam Turoff, Jim Tuttle
| bagit.txt data BagIt specification:
| bag-info.txt
bag-info.txt data http://www.ietf.org/internet-drafts/draft-kunze-bagit-03.txt
http://www.cdlib.org/inside/diglib/bagit/bagitspec.html
--- data/
data/ .mpg
BagIt was informed by
|
| my.pdf
my.pdf .pdf • Enclose-and-Deposit method, Tabata & Sugimoto,
|
| my.xsl
my.xsl .xls • LC’s eDeposit Pilot and NDIIPP AIHT
| my.mpg (http) • ARC/WARC aggregate file format
| my.mpg
Fig. 2. Payload directory, data,holds anything you want. Fig. 3. On the left is a bag received with missing files, or For further information
“Tag” files (purple) describe the bag itself, including list of “holes”. The “fetch.txt” file lists URLs and corresponding Please contact jak@ucop.edu or stephen.abrams@ucop.edu
files and checksums in the manifest (algorithms other than payload filenames that the receiver must fetch before For information on CDL’s Preservation Program, see
md5 possible) and an optional “bag-info.txt” metadata file. declaring the bag on the right complete. http://www.cdlib.org/programs/digital_preservation.html