PUBLIC-INBOX-V1-FORMAT(5)  public-inbox user manual  PUBLIC-INBOX-V1-FORMAT(5)

       public-inbox-v1-format - git repository and tree description (aka

       WARNING: this does NOT describe the scalable v2 format used by public-
       inbox.  Use of ssoma is not recommended for new installations due to
       scalability problems.

       ssoma uses a git repository to store each email as a git blob.  The
       tree filename of the blob is based on the SHA1 hexdigest of the first
       Message-ID header.  A commit is made for each message delivered.  The
       commit SHA-1 identifier is used by ssoma clients to track
       synchronization state.

       A Message-ID may be extremely long and also contain slashes, so using
       them as a path name is challenging.  Instead we use the SHA-1 hexdigest
       of the Message-ID (excluding the leading "<" and trailing ">") to
       generate a path name.  Leading and trailing white space in the Message-
       ID header is ignored for hashing.

       A message with Message-ID of: <>

       Would be stored as: f2/8c6cfd2b0a65f994c3e1be266105413b3d3f63

       Thus it is easy to look up the contents of a message matching a given a

       public-inbox v1 repositories currently do not resolve conflicting
       Message-IDs or messages with multiple Message-IDs.

       The Message-ID header is required.  "Bytes", "Lines" and "Content-
       Length" headers are stripped and not allowed, they can interfere with
       further processing.  When using ssoma with public-inbox-mda, the
       "Status" mbox header is also stripped as that header makes no sense in
       a public archive.

       flock(2) locking exclusively locks the empty $GIT_DIR/ssoma.lock file
       for all non-atomic operations.

       1. Message is delivered to a mail transport agent (MTA)

       1a. (optional) reject/discard spam, this should run before ssoma-mda

       1b. (optional) reject/strip unwanted attachments

       ssoma-mda handles all steps once invoked.

       2. Mail transport agent invokes ssoma-mda

       3. reads message via stdin, extracting Message-ID

       4. acquires exclusive flock lock on $GIT_DIR/ssoma.lock

       5. creates or updates the blob of associated 2/38 SHA-1 path

       6. updates the index and commits

       7. releases $GIT_DIR/ssoma.lock

       ssoma-mda can also be used as an inotify(7) trigger to monitor
       maildirs, and the ability to monitor IMAP mailboxes using IDLE will be
       available in the future.

       ssoma uses bare git repositories on both servers and clients.

       Using the git-init(1) command with --bare is the recommend method of
       creating a git repository on a server:

               git init --bare /path/to/wherever/you/want.git

       There are no standardized paths for servers, administrators make all
       the choices regarding git repository locations.

       Special files in $GIT_DIR on the server:

           An empty file for flock(2) locking.  This is necessary to ensure
           the index and commits are updated consistently and multiple
           processes running MDA do not step on each other.

           SQLite3 database maintaining a stable mapping of Message-IDs to
           NNTP article numbers.  Used by public-inbox-nntpd(1) and created
           and updated by public-inbox-index(1).

           Users of the PublicInbox::WWW interface will find it useful for
           attempting recovery from copy-paste truncations of URLs containing
           long Message-IDs.

           Automatically updated by public-inbox-mda(1), public-inbox-learn(1)
           and public-inbox-watch(1).

           Losing or damaging this file will cause synchronization problems
           for NNTP clients.  This file is expected to be stable and require
           no updates to its schema.

           Requires DBD::SQLite.

           Xapian database for search indices in the PSGI web UI.

           $N is the value of PublicInbox::Search::SCHEMA_VERSION, and
           installations may have parallel versions on disk during upgrades or
           to roll-back upgrades.

           This is created and updated by public-inbox-index(1).

           Automatically updated by public-inbox-mda(1), public-inbox-learn(1)
           and public-inbox-watch(1).

           This directory can always be regenerated with
           public-inbox-index(1).  If lost or damaged, there is no need to
           back it up unless the CPU/memory cost of regenerating it outweighs
           the storage/transfer cost.

           Since SCHEMA_VERSION 15 and the development of the v2 format, the
           "overview" DB also exists in the xapian directory for v1
           repositories.  See "OVERVIEW DB" in public-inbox-v2-format(5)

           Our use of the "OVERVIEW DB" requires Xapian document IDs to remain
           stable.  Using public-inbox-compact(1) and public-inbox-xcpdb(1)
           wrappers are recommended over tools provided by Xapian.

           This directory is large, often two to three times the size of the
           objects stored in a packed git repository.

           This file is no longer used or created by public-inbox, but it is
           updated if it exists to remain compatible with ssoma installations.

           A git index file used for MDA updates.  The normal git index (in
           $GIT_DIR/index) is not used at all as there is typically no working

       Each client $GIT_DIR may have multiple mbox/maildir/command targets.
       It is possible for a client to extract the mail stored in the git
       repository to multiple mboxes for compatibility with a variety of
       different tools.

       It is NOT recommended to check out the working directory of a git.
       there may be many files.

       It is impossible to completely expunge messages, even spam, as git
       retains full history.  Projects may (with adequate notice) cycle to new
       repositories/branches with history cleaned up via git-filter-repo(1) or
       git-filter-branch(1).  This is up to the administrators.

       Copyright 2013-2021 all contributors <>

       License: AGPL-3.0+ <>

       gitrepository-layout(5), ssoma(1)

public-inbox.git                  1993-10-02         PUBLIC-INBOX-V1-FORMAT(5)