Copy sparse files

cp --sparse=always <SRC> <DST>
This causes cp to detect and omit large blocks of nulls. Sparse files are useful for implying a lot of disk space without actually having to write it all out. You can use it in a pipe too: dd if=/dev/zero bs=1M count=5 |cp --sparse=always /dev/stdin SPARSE_FILE
Sample Output
# create a file with zeroes
$ dd if=/dev/zero bs=1M count=5 of=full-5m 
# copy with sparsity detection
$ cp --sparse=always full-5m sparse-5m

# they look the same...
$ ls -lah full-5m sparse-5m
-rw-r--r-- 1 h3xx users 5.0M Sep  7 03:05 full-5m
-rw-r--r-- 1 h3xx users 5.0M Sep  7 03:04 sparse-5m

# but they're different!
$ du -h full-5m sparse-5m
5.1M    full-5m
5.0K    sparse-5m

By: h3xx
2011-09-07 08:02:50

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

You must be signed in to comment.

What's this? is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.


Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: