MU INIT(1)

NAME

mu-init - initialize the mu message database

SYNOPSIS

mu [COMMON-OPTIONS] init [OPTIONS]

DESCRIPTION

mu init is the subcommand for setting up the mu message database. After mu init has completed, you can run mu index.

INIT OPTIONS

  -m, --maildir maildir

Use maildir as the root-maildir.

By default, mu uses the MAILDIR environment to find the root-maildir. If it is not set, it uses ~/Maildir if it is an existing directory. If neither of those can be used, the --maildir option is required; it must be an absolute path (but ~/ expansion is performed).

  --personal-address email-address-or-regex

Specifies that some e-mail address is a personal address. The option can be used multiple times, to specify all your addresses.

Any message in which at least one of the contact fields matches a personal address, is considered a `personal' message; this can then be used for filtering in mu-find(1), mu-cfind(1) and mu4e, e.g. to filter-out mailing list messages.

email-address-or-regex can be either a plain e-mail address (such as foo@example.com), or a basic PCRE regular-expression (see pcre(3) for details), wrapped in / (such as /foo-.*@example\.com/). Depending on your shell, the argument may need to be quoted.

A note of warning for mu4e users: any regular-expressions used with --with-address are also used by mu4e. Unfortunately, PCRE regular expressions are not generally compatible with Emacs regular expressions. For instance, (foo|bar) in PCRE syntax has as its Emacs equivalent.

The good news is that mu4e can automatically translate the regular-expressions, if you allow it to, by installing the pcre2el Elisp package. See the mu4e documentation for further details.

  --my-address email-address-or-regex

Obsolete alias for --personal-address

  --ignored-address email-address-or-regex

Specifies that some e-mail address is to be ignored from the contacts-cache (the option can be used multiple times). Such addresses then cannot be found with mu-cfind(1) or in the Mu4e contacts cache.

my-email-address can be either a plain e-mail address or a regexp, just like for the --personal-address option.

  --max-message-size size

Specifies the maximum size for an e-mail message. Usually, the default of 100000000 bytes should be fine.

  --batch-size size

The number of changes after which they are committed to the database; decreasing the value reduces the memory requirements, at the cost of make indexing substantially slower. Usually, the default of 250000 should be fine.

Batch-size 0 is interpreted as `use the default'.

  --support-ngrams

Whether to enable support for using ngrams in indexing and query parsing; this can be useful for languages without explicit word breaks, such as Chinese/Japanese/Korean. See NGRAM SUPPORT below for details.

  --reinit

Reinitialize the database from an earlier version; that is, create a new empty database with the existing settings. This cannot be combined with the other init options.

When you have labels defined for messages in your database, mu automatically exports those to file for importing later. See RESTORING LABELS below.

  --muhome

Use a non-default directory to store and read the database, write the logs, etc. By default, mu uses the XDG Base Directory Specification (e.g. on GNU/Linux this defaults to ~/.cache/mu and ~/.config/mu). Earlier versions of mu defaulted to ~/.mu, which now requires --muhome=~/.mu.

The environment variable MUHOME can be used as an alternative to --muhome. The latter has precedence.

NGRAM SUPPORT

mu's underlying Xapian database supports `ngrams', which improve searching for languages/scripts that do not have explicit word breaks, such as Chinese, Japanese and Korean. It is fairly intrusive, and influences both indexing and query-parsing; it is not enabled by default, and is recommended only if you need to search for messages written in such languages.

When enabled, mu automatically uses ngrams automatically. Xapian environment variables such as XAPIAN_CJK_NGRAM are ignored.

EXIT CODE

This command returns 0 upon successful completion, or a non-zero exit code otherwise.

0.  success

2.  no matches found. Try a different query

11. database schema mismatch. You need to re-initialize mu, see mu-init(1)

19. failed to acquire lock. Some other program has exclusive access to the mu database

99. caught an exception

RESTORING LABELS

When you have any labels defined for your database, mu automatically exports those to a file in the mu cache directory; you see this in the --init output.

    $ mu init --reinit
    exported labels to: /home/user/.cache/mu/mu-export-2025-08-16-13:43:27.txt

You can restore those labels after re-indexing, e.g.,
    $ mu label import /home/user/.cache/mu/mu-export-2025-08-16-13:43:27.txt

Please see mu-labels(1) for further details.

EXAMPLE
    $ mu init --maildir=~/Maildir --my-address=alice@example.com --my-address=bob@example.com --ignored-address='/.*reply.*/'

REPORTING BUGS

Please report bugs at https://github.com/djcb/mu/issues.

AUTHOR

Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>

COPYRIGHT

This manpage is part of mu 1.14.2.

Copyright © 2008-2026 Dirk-Jan C. Binnema. License GPLv3+: GNU GPL version 3 or later https://gnu.org/licenses/gpl.html. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

mu-index(1), mu-find(1), mu-labels(1), mu-cfind(1), pcre(3)