Linux guru wanted

Story line:

March 4th I powered up my laptop only to get a "no operating system found" message or something to that effect. Removed the drive and via a USB adapter hooked it up to another computer. Nothing. The drive did not exist.

My back-ups are such that I may have lost a few emails, nothing more. Most of the recovery data is on an exfat formatted external drive which means I lost time stamps etc. Everyone using the dos file system has experienced this short coming. My solution was two new hard drives formatted Linux ext4 for my back-up drives. Rebuild is pretty much complete.

My question: I'm using the cp command for the back-up process. Explicitly cp -R -T -u ~/source /path//destination
Do I need the -p switch.

Assuming source is a directory what is the difference between
cp -R -T -u ~/source /path//destination (label 1)
and
cp -R -T -u ~/source /path//destination/ (label 2) note the trailing /

From my experience (label 1) copies the files from directory source into directory destination while
(Label 2) copies the directory so you end up with destination/source

Can anyone confirm this.

Thanks
Rod

The trailing slash in a directory path doesn't matter. Linux is smart enough to know when a file is a directory or a regular file.

I think your problem is with the -T option. In 30 years of banging on Unix command lines, I've never used that option. I had to look it up.

From the man page for cp:
-T, --no-target-directory
treat DEST as a normal file

So it's the -T that's unpacking your directory and putting its contents in the new directory. Without the -T, you copy the whole directory and its contents into the DEST directory.

BTW, the -p option copies the file permissions and properties (date stamp and ownership, specifically) along with file itself. Without the -p option, the copied files appear as new files that belong to you with a new date stamp, regardless of when or by whom the original file was created.

Thanks. That explains one mystery. Through trial and error I've managed to add/remove the trailing / to get things to go where I want them to go. Still, I am concerned about the missing -p and what using it means for the -u option. Right now spot checks on files tell me the script works as intended. I am worried that adding the -p will break it.

For me, I have to decide if the time stamps are that important. My last back-up with accurate file time stamp data is February 6, 2022. Correcting time stamps. It can be done.

Of course, Murphy's Law kicked in. I had ordered/received two, what was described as external hard drives off Amazon. They turned out to be a memory chip with a fake file system. I was waiting for real drives to arrive when the crash occurred. Oh well.

Rod

Without seeing your code, I don't know if starting to use the -p option would mess up the results from the -u option, but a quick mental exercise makes me believe you'd probably be OK.

From the man page:
-u, --update
copy only when the SOURCE file is newer than the destination file or when the destination file is missing

The original file, from your card, will always be as old or older than any other copy of that file. I'm thinking -u should never find files older than ones already present in your backup set.

As always, keep a copy of your last good script, and test, test, test.

drsilver wrote in post #19371018
Without seeing your code, I don't know if starting to use the -p option would mess up the results from the -u option, but a quick mental exercise makes me believe you'd probably be OK.

From the man page:
-u, --update
copy only when the SOURCE file is newer than the destination file or when the destination file is missing

The original file, from your card, will always be as old or older than any other copy of that file. I'm thinking -u should never find files older than ones already present in your backup set.

As always, keep a copy of your last good script, and test, test, test.

The code is as above, copied here again cp -R -T -u ~/source /path/destination

My brother found the code on the net somewhere and sent it to me. I checked the man page, ran it with my then working computer every week for a few months and here we are.
There were no big question marks until my HD crashed and the need became real.

Thanks for the insights.

Rod

I guess to sort of close out this thread, I added the -p switch to the cp command and nothing blew up. Things appear to function as before per some spot checks after running the command.

Thank you drsilver for your assistance.

Rod