On 10/20/05, Randall R Schulz wrote:

Adam,

On Thursday 20 October 2005 14:49, adamvaz@earthlink.net wrote:

...

Hello from Adam in NYC w SUSE 10.

As long as you dont have active file access, like a browser looking a subdirectory of the usb drive or a xterm sitting doing the same, you just do sync: sync: sync: and unmount. If there is complaining, then you just boobooed.

Let's not propagate or encourage superstitious behavior, OK?

Syncing twice in a row is redundant. Syncing before unmounting is redundant. The kernel / FS code will carefully flush all modified internal structures and pending write buffers to the device before the sync(2) system call returns. The only reason to sync before shutting down is because the root file system cannot be unmounted.

For those of us that work in UNIX environments in addition to Linux it is safest to do the double sync. i.e In general it takes 2 syncs to ensure data is flushed, but with Linux it is safe to do only one. As to what gaureentees umount makes I don't know. I suspect that too is Linux/UNIX specific. I will probably continue my superstitious behaviour of calling sync before I disconnect a hot swappable drive. Greg -- Greg Freemyer The Norcross Group Forensics for the 21st Century

Randall R Schulz wrote:

Greg,

On Friday 21 October 2005 13:21, Greg Freemyer wrote:

...

On 10/20/05, Randall R Schulz wrote:

...

... For those of us that work in UNIX environments in addition to Linux it is safest to do the double sync. i.e In general it takes 2 syncs to ensure data is flushed, but with Linux it is safe to do only one.

Now, what's that expression??

Oh, yeah, that's it: BS!

I'm sorry, but nonsense is nonsense.

...

...

Greg

Randall Schulz

I don't know if this Mac Donalds advert appeared elsewhere in the States, but it was on TV in Northern California ... "Eddie the echo", the guy who repeated everything twice, until one day when he placed his order, to great surprise he didn't repeat it and was puzzled by the look on the young lady's face, then she said "Eddie, you didn't repeat your order", that's the stuff Unix myths are made of. I've seen most of my erstwhile colleagues hitting the enter key umpteen times every time before they type anything into an xterm on Solaris. This prompted me one day to ask a guy why they all do that, he said he didn't know and that was the way all the other guys did it. Regards Sid. -- Sid Boyce ... Hamradio License G3VBV, licensed Private Pilot Retired IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support Specialist Microsoft Windows Free Zone - Linux used for all Computing Tasks

On Saturday 22 October 2005 08:31, Greg Freemyer wrote:

At least do a "man 2 sync" and read it before you claim to understand it.

You will see that the UNIX standard calls for a double sync. It is a Linux _choice_ to implement it as a single sync.

OK, maybe this doesn't count because it was quite a long ago, but my very first solo SunOS 4.1.x command sequence was "sync sync halt" to bring the system down so I could install an internal SCSI drive. - Carl

On Fri, 21 Oct 2005 16:21:40 -0400 Greg Freemyer wrote:

For those of us that work in UNIX environments in addition to Linux it is safest to do the double sync. i.e In general it takes 2 syncs to ensure data is flushed, but with Linux it is safe to do only one.

As to what gaureentees umount makes I don't know. I suspect that too is Linux/UNIX specific. I will probably continue my superstitious behaviour of calling sync before I disconnect a hot swappable drive. Sync is a system call, and it's behavior is a bit different depending if you are SVID, Unix 98, Linux, ... A single sync should be sufficient on any system as long as you don't turn off the power. (Note that Unix people normally do: sync; sync; halt) since sync is asynchronous.

In general, I mostly prefer to umount a USB device because of my Unix background, but on the newer SuSE and Fedora distros it is not necessary. -- Jerry Feldman Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9

* Greg Freemyer [10-21-05 15:12]:

FYI: The "sync" option has been standard for automount since 9.1 I think.

My 9.0 version automatically includes sync in /etc/fstab on hotplugged hard drives and memory cards. -- Patrick Shanahan Registered Linux User #207535 http://wahoo.no-ip.org @ http://counter.li.org HOG # US1244711 Photo Album: http://wahoo.no-ip.org/gallery2