bup-index - print and/or update the bup filesystem index
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] <paths...>
bup index manipulates the filesystem index, which is a cache of absolute paths and their metadata (atttributes, SHA-1 hashes, etc.). The bup index is similar in function to the
git(1) index, and the default index can be found in
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:
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
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.
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).
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.
--updateis the default, and paths may be excluded by the
-p. The codes mean, respectively, that a file is marked in the index as added, modified, deleted, or unchanged since the last backup.
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
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)
-v, print each directory as it is updated; with two
-v, print each file too.
bup index -vux /etc /var /usr
Part of the