为什么Python脚本在首次启动时从rc.local运行时不可靠？

Question

下面这个脚本在以root用户登录并从命令行运行时效果很好，但在Ubuntu 10.04的首次启动时通过/etc/rc.local运行时，大约有25%的几率会失败。系统的root用户、mysql的root用户和一些mysql用户的密码设置得都没问题，但有一个会失败，控制台日志显示标准的mysql登录错误：“ERROR 1045 (28000): 访问被拒绝，用户 'root' @ 'localhost'（使用密码：是）”。

在从初始化任务运行python脚本时，有什么我需要注意的，比如环境变量之类的吗？

#!/usr/bin/env python 
# Randomizes and outputs to files the system root and mysql user passwords 
files = ['/home/ubuntu/passwords','/opt/data1/alfresco/extensions/ 
extension/alfresco-global.properties','/opt/data/etc/mysql/ 
debian.cnf','/home/ubuntu/duncil'] 
userpasswords = {'root':'ROOTPASSWORD'} 
mysqlpasswords = 
{'root':'MYSQLPASSWORD','alfresco':'alfrescoPASSWORD','debian-sys- 
maint':'debian-sys-maintPASSWORD'} 
otherpasswords = ['OTHERPASSWORD'] 
log = '/var/log/firstrun' 
import random, string 
import crypt 
import re 
from subprocess import PIPE, Popen 
def getsalt(chars = string.letters + string.digits): 
    # generate a random 2-character 'salt' 
    return random.choice(chars) + random.choice(chars) 
def getpwd(chars = string.letters + string.digits, len = 12): 
    retval = ""; 
    for i in range(0, len): 
    # generate 12 character alphanumeric password 
        retval += random.choice(chars) 
    return retval 
def replace_pass(filename): 
    handle = open(filename, 'r') 
    hbuf = handle.read() 
    handle.close() 
    for placeholder, password in pdict.iteritems(): 
        hbuf = re.sub(placeholder, password, hbuf) 
    try: 
        # Output file 
        handle = open(filename, 'w') 
        handle.write(hbuf) 
        handle.close() 
    except: 
        pass 
        #logh.write('failed to update ' + filename  + "\n") 
        #logh.write('maybe you don\'t have permision to write to it?\n') 
logh = open(log, "a") 
logh.write("Starting...\n") 
# Generate passwords 
pdict = {} 
for user, placeholder in userpasswords.iteritems(): 
    syspass = getpwd() 
    Popen(['usermod', '--password', crypt.crypt(syspass, getsalt()), user]) 
    logh.write(placeholder + ": User " + user + " --> " + syspass + "\n") 
    pdict[placeholder] = syspass 
# Whats the MySQL Root password placeholder? 
mplace = mysqlpasswords['root'] 
for user, placeholder in mysqlpasswords.iteritems(): 
    mpass = getpwd() 
    if (("root" in mysqlpasswords) and (mysqlpasswords['root'] in pdict)): 
        mrootpass = pdict[mysqlpasswords['root']] 
    else: 
        mrootpass = "" 
    Popen(['mysql', '-uroot', "--password=" + mrootpass, "-e", "UPDATE user SET Password = PASSWORD('" + mpass + "') WHERE User = '" + user + "';FLUSH PRIVILEGES;","mysql"]) 
    logh.write(placeholder + ": MySQL " + user + " --> " + mpass + "\n") 
    pdict[placeholder] = mpass 
for placeholder in otherpasswords: 
    opass = getpwd() 
    logh.write(placeholder + ": " + opass + "\n") 
    pdict[placeholder] = opass 
# Update passwords 
for file in files: 
    logh.write("Replacing placeholders in " + file + "\n") 
    replace_pass(file) 
logh.write("Finished\n") 
logh.close 

Answer 1

难道 Popen 不是异步执行的吗？

看起来在启动的时候，系统负担很重，你可能遇到了一个竞争条件，也就是在设置根密码和用这个密码去设置下一个密码（下一个命令）之间发生了冲突。

试试这个

p = Popen(['mysql', '-uroot', "--password=" + mrootpass, "-e", "UPDATE user SET Password = PASSWORD('" + mpass + "') WHERE User = '" + user + "';FLUSH PRIVILEGES;","mysql"])
p.wait()

看看这样是否能解决问题。