Re: [gentoo-user] [OT] how to delete a directory tree really fast

[Helmut Jarausch]

Many thanks to Rich, Miles, Vitor and Laurence for their hints on this  
subject.
Especially the suggestion to use BTRFS Snapshots was very helpful.

Finally I have come up with the following shell script for backing up  
my /home directory,
comments are more than welcome, of course.
(/HBackUp contains a BTRFS file system)


#!/bin/zsh
mount /HBackUp
pushd /HBackUp
NUM_TO_KEEP=5
if [ -d "ohome_$NUM_TO_KEEP" ]
then
     btrfs subvolume delete "ohome_$NUM_TO_KEEP"
fi

if ! [ -f _RSync_Failed ]
then
     for backup_no in $(seq $((NUM_TO_KEEP-1)) -1 1)
     do
         if [ -d ohome_$backup_no ]
         then
             backup_no_plus_1="$((backup_no+1))"
             mv $ohome_prev "ohome_$backup_no_plus_1"
         fi
     done
     if ! btrfs subvolume snapshot ohome ohome_1
     then
         echo Sorry, creating snapshot ohome_1 failed 1>&2
         exit 1
     fi
fi

RSync_OK=False
touch _RSync_Failed

popd
pushd /home

if rsync -aqxAHSW --delete  . /HBackUp/ohome/
then
   RSync_OK=True
else
     case "$?" in
         23)
             # This means some files gave permission denied - assume  
that's OK
             RSync_OK=True
             ;;
         24)
             # This means one or more files disappeared
             RSync_OK=True
             ;;
         *)
             echo rsync failed. Exit code was $?"
             ;;
     esac
fi

popd

cd /HBackUp

case "$RSync_OK" in
     True)
         rm _RSync_Failed
         ;;
     False)
         cd /
        umount  /HBackUp
         exit 1
         ;;
esac

cd /
umount /HBackUp