From: usenet@writer.com   
      
   On 11/2/2023 3:39 AM, Paul wrote:   
   > On 11/2/2023 3:52 AM, bilsch01 wrote:   
   >> Hello, I was never very good at linux scripting, and now I've forgotten   
   much what I did know. I hope somebody here can help me incorporate gzip with   
   the dd copy lines I use for backing up laptop to an external drive. The two   
   different thumb drives I    
   use to boot laptop and copy SDD are   
   >> 1) Ubuntu Installer and 2) Knoppix.  Both of those come with gzip.   
   >> I've never actually ever used gzip.   
   >>   
   >> Here's the lines I use to copy the SDD contents to an external drive:   
   >>   
   >> ## first do fdisk -l to sort out the devices   
   >> sudo mkdir -p /mnt/sdb1  (creating a mount point)   
   >> sudo mount -t ntfs /dev/sdb1 /mnt/sdb1   
   >> sudo mkdir -p /mnt/sdb1/images (if u don't already have that directory)   
   >> sudo dd if=/dev/nvme0n1 of=/mnt/sdb1/images/asyymmdd.img bs=4096   
   conv=notrunc,noerror   
   >>   
   >> Here's the lines to restore the SDD if I ever need to:   
   >>   
   >> sudo mkdir -p /mnt/sdb1  (creating a mount point)   
   >> sudo mount -t ntfs /dev/sdb1 /mnt/sdb1   
   >> sudo dd if=/mnt/sdb1/images/asyymmdd.img of=/dev/nvme0n1 bs=4096   
   conv=notrunc,noerrer   
   >>   
   >> Thanks in advance.   
   >> Bill S.   
   >>   
   >   
   > sudo dd if=/dev/nvme0n1 of=/mnt/sdb1/images/asyymmdd.img bs=4096   
   conv=notrunc,noerror   
   >   
   > becomes   
   >   
   >     sudo dd if=/dev/nvme0n1 bs=4096 conv=notrunc,noerror | gzip -3 >   
   /mnt/sdb1/images/asyymmdd.img.gz   
   >   
   > The dd program, when you remove the "of" specification, uses STDOUT.   
   >   
   > GZIP accepts piped input. There are options of --fast and --slow which   
   > correspond to -1 and -9. The value -3 for compression is the default,   
   > and is shown as an example of a passed parameter. You might want to   
   > test the output, and see if the size changes or not   
   >   
   >      ... | gzip -1 | wc -c     # count the bytes of output   
   >   
   >      ... | gzip -9 | wc -c     # count the bytes of output   
   >   
   > With gzip, you have to be careful of the syntax,   
   > so the original file is not deleted. That's what I spent   
   > most of my time playing with, is checking for deletion.   
      
   Can you be more specific about what syntax will result in deletion of   
   original file?   
   Thank you.   
      
      
   >   
   > *******   
   >   
   > Later:   
   >   
   >     gzip -c -d /mnt/sdb1/images/asyymmdd.img.gz | sudo dd of=/dev/nvme0n1   
   bs=4096 conv=notrunc,noerrer   
   >   
   > The -c sends the output to STDOUT.   
   > The -d says "switch to decompression mode".   
   > The input file is a compressed one.   
   > Sending to STDOUT, also stops deletion of the input file.   
   >   
   > The dd command, when there is no "if" specification, it inputs from STDIN.   
   >   
   > The output file, the target, is the nvme.   
   >   
   > *******   
   >   
   > An alternate compressor you can try, is "pigz".   
   >   
   >     sudo apt install pigz   
   >     man pigz   
   >   
   > Syntax is the same as gzip, and it accepts a  -p 4   
   > parameter, which is the number of processor   
   > cores to use for compression.   
   >   
   > If you use exactly the same compression syntax as the   gzip -3   
   > example, it uses all the cores on your CPU.   
   >   
   >     pigz -3           # On a 4C 8T processor, the default is -p 8   
   >   
   > pigz output is ".gz" as before. gzip can be used for decompression.   
   > pigz can be used for decompression. But during decompression, it   
   > only uses one core. One claim I've seen, is decompression is typically   
   > faster, so the lack of multithreading is not the end of the world.   
   > It is compression that needs the horsepower.   
   >   
   > You can use "top" or "gnome-system-monitor" to monitor the amount   
   > of CPU usage during compression.   
   >   
   > Anyway, I'm sure you have a whole collection of compressor commands.   
   > There are compressors to produce smaller output, but they don't   
   > run as fast.   
   >   
   >     Paul   
      
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