linux time synchronization (linux 时间同步设置)

1.check ntp is installed or not
[root@myvm1 server-tar]# whereis npt
npt:
#:(..not install
2.get ntp from official website(http://psp2.ntp.org/bin/view/Main/SoftwareDownloads) and install.
[root@myvm1 server-tar]# wget http://archive.ntp.org/ntp4/ntp-4.2/ntp-4.2.6.tar.gz
[root@myvm1 server-tar]#cp ntp-4.2.6.tar.gz ../
[root@myvm1 server-tar]#cd ..
[root@myvm1 server-tar]#tar -zxvf ntp-4.2.6.tar.gz
[root@myvm1 server-tar]#cd ntp-4.2.6
[root@myvm1 ntp-4.2.6]# vim README
[root@myvm1 ntp-4.2.6]# vim INSTALL
[root@myvm1 ntp-4.2.6]# ./configure --help
######################
By default, `make install' will install all the files in
`/usr/local/bin', `/usr/local/lib' etc.  You can specify
an installation prefix other than `/usr/local' using `--prefix',
for instance `--prefix=$HOME'.
######################
i will install it in the path "/usr/local/ntp"
[root@myvm1 ntp-4.2.6]# mkdir /usr/local/ntp
[root@myvm1 ntp-4.2.6]# ./configure --prefix=/usr/local/ntp
[root@myvm1 ntp-4.2.6]# make
[root@myvm1 ntp-4.2.6]# make install
[root@myvm1 ntp-4.2.6]# whereis ntp
ntp: /usr/local/ntp
#synchronization time from time server(time.nist.gov).
[root@myvm1 ntp-4.2.6]# date
Tue Feb  2 18:59:22 CST 2010
[root@myvm1 ntp-4.2.6]# /usr/local/ntp/bin/ntpdate time.nist.gov
[root@myvm1 ntp-4.2.6]# hwclock -w
#write time into bios
[root@myvm1 ntp-4.2.6]# date             
Sat Feb 20 10:29:59 CST 2010
#successful!
#you must create crontab list to make sure synchronize time.
#########
#Update Time Everyday
0 0 * * * /usr/local/ntp/bin/ntpdate time.nist.gov > /dev/null 2>&1