On Tue, 2010-11-09 at 17:58 -0300, Fernando Cassia wrote:
> Yes, FTP would be the better choice to ensure file integrity. A decade
> ago I was a fundamentalist and used to write every time I saw a large
> program file linked on web servers over HTTP telling them to "create a
> FTP server" and that "the ftp protocol exists for a reason".
Fernando,
Yes and no. The integrity of FTP transmissions are based solely on TCP
checksums and retransmissions. Rsync and torrent are also TCP protocols,
but they have powerful integrity-tracking mechanisms of their own in
addition to TCP's. If you have access to a remote rsync server, a local
rsync client may be your best choice to guarantee perfect delivery. It
will repair on-the-fly any possibly-corrupted iso file you already have
in far less time than a ftp retransmisison. Suggest moving the DVD iso
file you have to your Downloads directory and trying the following
(note: some rsync sites do not support the -c option):
$ time rsync -acvxzHP --no-motd rsync://rsync.gtlib.gatech.edu/fedora-linux-releases/14/Fedora/i386/iso/Fedora-14-i386-DVD.iso ~/Downloads/
# where the rsync man page defines the dash options as:
# -a archive mode; same as -rlptgoD (no -H)
# -r recurse into directories
# -l copy symlinks as symlinks
# -p preserve permissions
# -t preserve modification times
# -g preserve group
# -o preserve owner (super-user only)
# -D same as --devices --specials
# --devices preserve device files (super-user only)
# --specials preserve special files
# -c skip based on checksum, not mod-time & size
# -v increase verbosity
# -x don’t cross filesystem boundaries
# -z compress file data during the transfer
# -H preserve hard links
# -P same as --partial --progress
# --partial keep partially transferred files
# --progress show progress during transfer
# --no-motd suppress daemon-mode MOTD (see caveat)
I have fast service (12 Mbps) and get the following result for an
already-perfect DVD iso file:
receiving file list ...
1 file to consider
sent 151 bytes received 1063 bytes 5.07 bytes/sec
total size is 3561752576 speedup is 2933898.33
real 3m59.060s
user 0m12.592s
sys 0m3.648s
Hope this helps.
--Doc Savage
Fairview Heights, IL
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