Detailed explanation of full backup and differential backup of files in Python

Python实现文件的全备份和差异备份

之前有写利用md5方式来做差异备份，但是这种md5方式来写存在以下问题：

md5sum获取有些软连接的MD5值存在问题

不支持对空目录进行备份，因为md5sum无法获取空目录的md5值

权限的修改md5sum无法判断

解决方案：

利用文件的mtime ctime

mtime（Modified time）是在写入文件时随文件内容的更改而更改的

ctime（Create time）是在写入文件、更改所有者、权限或链接设置时随Inode的内容更改而更改的

废话不多说直接上代码：

#!/usr/bin/env python
import time,os,sys,cPickle
fileInfo = {}
def logger(time,fileName,status,fileNum):
  f = open('backup.log','a')
  f.write("%s\t%s\t%s\t\t%s\n" % (time,fileName,status,fileNum))
def tar(sDir,dDir,fileNum):
  command = "tar zcf %s %s >/dev/null 2>&1" % (dDir + ".tar.gz",sDir)
  if os.system(command) == 0:
    logger(time.strftime('%F %X'),dDir + ".tar.gz",'success',fileNum)
  else:
    logger(time.strftime('%F %X'),dDir + ".tar.gz",'failed',fileNum)
def fullBak(path):
  fileNum = 0
  for root,dirs,files in os.walk(path):
    for name in files:
      file = os.path.join(root, name)
      mtime = os.path.getmtime(file)
      ctime = os.path.getctime(file)
      fileInfo[file] = (mtime,ctime)
      fileNum += 1
  f = open(P,'w')
  cPickle.dump(fileInfo,f)
  f.close()
  tar(S,D,fileNum)
def diffBak(path):
  for root,dirs,files in os.walk(path):
    for name in files:
      file = os.path.join(root,name)
      mtime = os.path.getmtime(file)
      ctime = os.path.getctime(file)
      fileInfo[file] = (mtime,ctime)
  if os.path.isfile(P) == 0:
    f = open(P,'w')
    f.close()
  if os.stat(P).st_size == 0:
    f = open(P,'w')
    cPickle.dump(fileInfo,f)
    fileNum = len(fileInfo.keys())
    f.close()
    print fileNum
    tar(S,D,fileNum)
  else:
    f = open(P)
    old_fileInfo = cPickle.load(f)
    f.close()
    difference = dict(set(fileInfo.items())^set(old_fileInfo.items()))
    fileNum = len(difference)
    print fileNum
    difference_file = ' '.join(difference.keys())
    print difference_file
    tar(difference_file,D,fileNum)
    f = open(P,'w')
    cPickle.dump(fileInfo,f)
    f.close()
def Usage():
  print '''
    Syntax: python file_bakcup.py pickle_file model source_dir filename_bk
      model: 1:Full backup 2:Differential backup
    example: python file_backup.py fileinfo.pk 2 /etc etc_$(date +%F)
      explain: Automatically add '.tar.gz' suffix
  '''
  sys.exit()
if len(sys.argv) != 5:
  Usage()
P = sys.argv[1]
M = int(sys.argv[2])
S = sys.argv[3]
D = sys.argv[4]
if M == 1:
  fullBak(S)
elif M == 2:
  diffBak(S)
else:
  print "\033[;31mDoes not support this mode\033[0m"
  Usage()

测试：

$ python file_backup.py data.pk 1 data data_$(date +%F) #全备份
$ > data/www.linuxeye.com #测试创建文件，修改文件权限
$ chmod 777 data/py/eshop_bk/data.db
$ python file_backup.py data.pk 2 data data_$(date +%F)_1 #备份改变的文件
2
data/py/eshop_bk/data.db data/www.linuxeye.com

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