Does this failure to behave as one might hope perhaps constitute a bug in a widely used admin utility?
Erik Johnson On Wed, Jan 7, 2009 at 4:00 PM, Larry Ploetz <[email protected]> wrote: > On 1/7/09 1:44 PM, John Summerfield wrote: >> >> I see no reason logrotate should not handle sparse files well when >> copying them. > > Yeah, there's no reason why it shouldn't, but it doesn't (see my empiric > test in previous post). > >> >> 06:42 [sum...@numbat ~]$ cp --help | grep sparse >> --sparse=WHEN control creation of sparse files >> >> This is probably the best way of cleaning the NULs people are concerned >> about. > > I've always interpreted "crude heuristic" to mean that cp reads all the > virtual \x00's, but writes sparsely. Since what I want with sparse log > files, where the sparse-ness is always at the beginning (corresponding > to the previously archived portions of the log file), this didn't seem > as efficient as skipping over the beginning blocks that were only sparse: > > $ man cp | grep -iwC1 sparse > --sparse=WHEN > control creation of sparse files > > -- > > By default, sparse SOURCE files are detected by a crude > heuristic and > the corresponding DEST file is made sparse as well. That > is the > behavior selected by --sparse=auto. Specify --sparse=always to > create > a sparse DEST file whenever the SOURCE file contains a long > enough > sequence of zero bytes. Use --sparse=never to inhibit > creation of > sparse files. > > And since it's so easy to determine which block first contains real > data, I figured, "why not start copying there?" > > Again, this is only for log files -- only appended to, for when they get > sparse because of logrotate copytruncate or "> filename" or similar > truncation, sparse-ness at the beginning of the file. > > - Larry > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO LINUX-390 or > visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
