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bup-margin(1) [debian man page]

bup-margin(1)						      General Commands Manual						     bup-margin(1)

NAME
bup-margin - figure out your deduplication safety margin SYNOPSIS
bup margin [options...] DESCRIPTION
bup margin iterates through all objects in your bup repository, calculating the largest number of prefix bits shared between any two entries. This number, n, identifies the longest subset of SHA-1 you could use and still encounter a collision between your object ids. For example, one system that was tested had a collection of 11 million objects (70 GB), and bup margin returned 45. That means a 46-bit hash would be sufficient to avoid all collisions among that set of objects; each object in that repository could be uniquely identified by its first 46 bits. The number of bits needed seems to increase by about 1 or 2 for every doubling of the number of objects. Since SHA-1 hashes have 160 bits, that leaves 115 bits of margin. Of course, because SHA-1 hashes are essentially random, it's theoretically possible to use many more bits with far fewer objects. If you're paranoid about the possibility of SHA-1 collisions, you can monitor your repository by running bup margin occasionally to see if you're getting dangerously close to 160 bits. OPTIONS
--predict Guess the offset into each index file where a particular object will appear, and report the maximum deviation of the correct answer from the guess. This is potentially useful for tuning an interpolation search algorithm. --ignore-midx don't use .midx files, use only .idx files. This is only really useful when used with --predict. EXAMPLE
$ bup margin Reading indexes: 100.00% (1612581/1612581), done. 40 40 matching prefix bits 1.94 bits per doubling 120 bits (61.86 doublings) remaining 4.19338e+18 times larger is possible Everyone on earth could have 625878182 data sets like yours, all in one repository, and we would expect 1 object collision. $ bup margin --predict PackIdxList: using 1 index. Reading indexes: 100.00% (1612581/1612581), done. 915 of 1612581 (0.057%) SEE ALSO
bup-midx(1), bup-save(1) BUP
Part of the bup(1) suite. AUTHORS
Avery Pennarun <apenwarr@gmail.com>. Bup unknown- bup-margin(1)

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bup-on(1)						      General Commands Manual							 bup-on(1)

NAME
bup-on - run a bup server locally and client remotely SYNOPSIS
bup on <hostname> index ... bup on <hostname> save ... bup on <hostname> split ... DESCRIPTION
bup on runs the given bup command on the given host using ssh. It runs a bup server on the local machine, so that commands like bup save on the remote machine can back up to the local machine. (You don't need to provide a --remote option to bup save in order for this to work.) See bup-index(1), bup-save(1), and so on for details of how each subcommand works. This 'reverse mode' operation is useful when the machine being backed up isn't supposed to be able to ssh into the backup server. For example, your backup server can be hidden behind a one-way firewall on a private or dynamic IP address; using an ssh key, it can be autho- rized to ssh into each of your important machines. After connecting to each destination machine, it initiates a backup, receiving the resulting data and storing in its local repository. For example, if you run several virtual private Linux machines on a remote hosting provider, you could back them up to a local (much less expensive) computer in your basement. EXAMPLES
# First index the files on the remote server $ bup on myserver index -vux /etc bup server: reading from stdin. Indexing: 2465, done. bup: merging indexes (186668/186668), done. bup server: done # Now save the files from the remote server to the # local $BUP_DIR $ bup on myserver save -n myserver-backup /etc bup server: reading from stdin. bup server: command: 'list-indexes' PackIdxList: using 7 indexes. Saving: 100.00% (241/241k, 648/648 files), done. bup server: received 55 objects. Indexing objects: 100% (55/55), done. bup server: command: 'quit' bup server: done # Now we can look at the resulting repo on the local # machine $ bup ftp 'cat /myserver-backup/latest/etc/passwd' root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/bin/sh bin:x:2:2:bin:/bin:/bin/sh sys:x:3:3:sys:/dev:/bin/sh sync:x:4:65534:sync:/bin:/bin/sync ... SEE ALSO
bup-index(1), bup-save(1), bup-split(1) BUP
Part of the bup(1) suite. AUTHORS
Avery Pennarun <apenwarr@gmail.com>. Bup unknown- bup-on(1)

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