well, I suggest you read the source code for cp and mv
well, for a start, cp copies the file, so opens, reads and copies. mv just moves or renames it. So the actual inode is not accessed,
only the Directory entries.
---------- Post updated at 12:16 PM ---------- Previous update was at 12:10 PM ----------
Quote:
Originally Posted by achenle
The mv command first deletes the target file if it exists. The cp command does not.
no that is wrong.
observe, if I mv (rename) a file the inode
does not change:
/*
* one-way-pipe.c - example of using a pipe to communicate data between a
* process and its child process. The parent reads input
* from the user, and sends it to the child via a pipe.
* The child prints the received data to the... (1 Reply)
OK, I've used various versions of UNIX(Solaris, HPUX, etc..) over the years. Now the organization I work for is leaning towards more Linux based systems(Redhat, Suse, etc..)
I do see differences in in comands and how to accomplish basic adminstration, but nothing mind blowing.
So, what is it... (5 Replies)
Hello all
the su with -l option is running normal with linux but when i try to run it on unix AIX 5.2.7 it's not working with -l option
any help (6 Replies)
Moving from AIX 6.1 to RHEL 6.6, I have noticed a few command differences.
One that has been causing issue is a simple echo command when I have to use it this way -> "echo -e"
On the AIX it outputs to "-e" but since RHEL has "-e" as an option for echo and hence it outputs to blank here.
All... (3 Replies)
Discussion started by: aster007
3 Replies
LEARN ABOUT DEBIAN
bup-margin
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)