1. gen hash file for master
   • copy scripts to master
   • 'bash syncDir.sh genHashOfMaster'
2. move slave files to correct path
   • copy scripts to slave
   • copy masterHash.txt to slave directory
   • 'bash syncDir.sh genHashOfSlave'
   • 'bash syncDir.sh moveByMasterHash'
   • 'bash syncDir.sh genHashOfSlave'
   • 'comm -23 masterHash.txt slaveHash.txt > masterPrivateHash.txt' or 'bash syncDir.sh genPrivateHashOfMaster'
3. backup private files of master
   • copy masterPrivateHash.txt to master directory
   • 'bash syncDir.sh backupPrivateFilesOfMater'
4. restore private files of master to slave
   • copy backup directory to slave
   • 'bash syncDir.sh restorePrivateFilesOfMasterToSlave'
5. cleanup
   • cd master directory
   • 'bash syncDir.sh cleanup'
   • cd slave directory
   • 'bash syncDir.sh cleanup'
6. swap the master and slave, redo things above