bup-index - Online in the Cloud

PROGRAM:

NAME

bup-index - print and/or update the bup filesystem index

SYNOPSIS

bup index <-p|-m|-s|-u|--clear|--check> [-H] [-l] [-x] [--fake-valid] [--no-check-device]
[--fake-invalid] [-f indexfile] [--exclude path] [--exclude-from filename] [--exclude-rx
pattern] [--exclude-rx-from filename] [-v] <filenames...>

DESCRIPTION

bup index prints and/or updates the bup filesystem index, which is a cache of the
filenames, attributes, and sha-1 hashes of each file and directory in the filesystem. The
bup index is similar in function to the git(1) index, and can be found in
$BUP_DIR/bupindex.

Creating a backup in bup consists of two steps: updating the index with bup index, then
actually backing up the files (or a subset of the files) with bup save. The separation
exists for these reasons:

1. There is more than one way to generate a list of files that need to be backed up. For
example, you might want to use inotify(7) or dnotify(7).

2. Even if you back up files to multiple destinations (for added redundancy), the file
names, attributes, and hashes will be the same each time. Thus, you can save the
trouble of repeatedly re-generating the list of files for each backup set.

3. You may want to use the data tracked by bup index for other purposes (such as speeding
up other programs that need the same information).

NOTES

At the moment, bup will ignore Linux attributes (cf. chattr(1) and lsattr(1)) on some
systems (any big-endian systems where sizeof(long) < sizeof(int)). This is because the
Linux kernel and FUSE currently disagree over the type of the attr system call arguments,
and so on big-endian systems there's no way to get the results without the risk of stack
corruption (http://lwn.net/Articles/575846/). In these situations, bup will print a
warning the first time Linux attrs are relevant during any index/save/restore operation.

bup makes accommodations for the expected "worst-case" filesystem timestamp resolution --
currently one second; examples include VFAT, ext2, ext3, small ext4, etc. Since bup
cannot know the filesystem timestamp resolution, and could be traversing multiple
filesystems during any given run, it always assumes that the resolution may be no better
than one second.

As a practical matter, this means that index updates are a bit imprecise, and so bup save
may occasionally record filesystem changes that you didn't expect. That's because, during
an index update, if bup encounters a path whose actual timestamps are more recent than one
second before the update started, bup will set the index timestamps for that path (mtime
and ctime) to exactly one second before the run, -- effectively capping those values.

This ensures that no subsequent changes to those paths can result in timestamps that are
identical to those in the index. If that were possible, bup could overlook the
modifications.

You can see the effect of this behavior in this example (assume that less than one second
elapses between the initial file creation and first index run):

$ touch src/1 src/2
# A "sleep 1" here would avoid the unexpected save.
$ bup index src
$ bup save -n src src # Saves 1 and 2.
$ date > src/1
$ bup index src
$ date > src/2 # Not indexed.
$ bup save -n src src # But src/2 is saved anyway.

Strictly speaking, bup should not notice the change to src/2, but it does, due to the
accommodations described above.

MODES

-u, --update
recursively update the index for the given filenames and their descendants. One or
more filenames must be given. If no mode option is given, this is the default.

-p, --print
print the contents of the index. If filenames are given, shows the given entries
and their descendants. If no filenames are given, shows the entries starting at
the current working directory (.).

-m, --modified
prints only files which are marked as modified (ie. changed since the most recent
backup) in the index. Implies -p.

-s, --status
prepend a status code (A, M, D, or space) before each filename. Implies -p. The
codes mean, respectively, that a file is marked in the index as added, modified,
deleted, or unchanged since the last backup.

--check
carefully check index file integrity before and after updating. Mostly useful for
automated tests.

--clear
clear the default index.

OPTIONS

-H, --hash
for each file printed, prepend the most recently recorded hash code. The hash code
is normally generated by bup save. For objects which have not yet been backed up,
the hash code will be 0000000000000000000000000000000000000000. Note that the hash
code is printed even if the file is known to be modified or deleted in the index
(ie. the file on the filesystem no longer matches the recorded hash). If this is
a problem for you, use --status.

-l, --long
print more information about each file, in a similar format to the -l option to
ls(1).

-x, --xdev, --one-file-system
don't cross filesystem boundaries when recursing through the filesystem -- though
as with tar and rsync, the mount points themselves will still be indexed. Only
applicable if you're using -u.

--fake-valid
mark specified filenames as up-to-date even if they aren't. This can be useful for
testing, or to avoid unnecessarily backing up files that you know are boring.

--fake-invalid
mark specified filenames as not up-to-date, forcing the next "bup save" run to
re-check their contents.

-f, --indexfile=indexfile
use a different index filename instead of $BUP_DIR/bupindex.

--exclude=path
exclude path from the backup (may be repeated).

--exclude-from=filename
read --exclude paths from filename, one path per-line (may be repeated). Ignore
completely empty lines.

--exclude-rx=pattern
exclude any path matching pattern, which must be a Python regular expression
(http://docs.python.org/library/re.html). The pattern will be compared against the
full path, without anchoring, so "x/y" will match "ox/yard" or "box/yards". To
exclude the contents of /tmp, but not the directory itself, use "^/tmp/.". (may be
repeated)

Examples:

· '/foo$' - exclude any file named foo

· '/foo/$' - exclude any directory named foo

· '/foo/.' - exclude the content of any directory named foo

· '^/tmp/.' - exclude root-level /tmp's content, but not /tmp itself

--exclude-rx-from=filename
read --exclude-rx patterns from filename, one pattern per-line (may be repeated).
Ignore completely empty lines.

--no-check-device
don't mark a an entry invalid if the device number (stat(2) st_dev) changes. This
can be useful when indexing remote, automounted, or (LVM) snapshot filesystems.

-v, --verbose
increase log output during update (can be used more than once). With one -v, print
each directory as it is updated; with two -v, print each file too.

EXAMPLES

bup index -vux /etc /var /usr

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