From 4e34468880397891de82b936747b5ce9cbceb2de Mon Sep 17 00:00:00 2001 From: wangjiezhe Date: Tue, 21 Oct 2014 00:39:38 +0800 Subject: [PATCH] [translated]20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md --- ...and time from the command line on Linux.md | 86 ------------------- ...and time from the command line on Linux.md | 84 ++++++++++++++++++ 2 files changed, 84 insertions(+), 86 deletions(-) delete mode 100644 sources/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md create mode 100644 translated/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md diff --git a/sources/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md b/sources/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md deleted file mode 100644 index 30f46eb846..0000000000 --- a/sources/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md +++ /dev/null @@ -1,86 +0,0 @@ -wangjiezhe translating... - -Linux FAQs with Answers--How to change date and time from the command line on Linux -================================================================================ -> **Question**: In Linux, how can I change date and time from the command line? - -Keeping the date and time up-to-date in a Linux system is an important responsibility of every Linux user and system administrator. Many applications rely on accurate timing information to operate properly. Besides, inaccurate date and time render timestamp information in log files meaningless, diminishing their usefulness for system inspection and troubleshooting. For production systems, accurate date and time are even more critical. For example, the production in a retail company must be accounted precisely at all times (and stored in a database server) so that the finance department can calculate the expenses and net income of the day, current week, month, and year. - -We must note that there are two kinds of clocks in a Linux machine: the software clock (aka system clock), which is maintained by the kernel, and the (battery-driven) hardware clock, which is used to keep track of time when the machine is powered down. During boot, the kernel sets the system clock to the same time as the hardware clock. Afterwards, both clocks run independent from each other. - -### Method One: Date Command ### - -In Linux, you can use the date command to change the date and time of your system: - - # date --set='NEW_DATE' - -where NEW_DATE is a mostly free format human readable date string such as "Sun, 28 Sep 2014 16:21:42" or "2014-09-29 16:21:42". - -The date format can also be specified to obtain more accurate results: - - # date +FORMAT --set='NEW_DATE' - -For example: - - # date +’%Y%m%d %H%m’ --set='20140928 1518' - -![](https://farm3.staticflickr.com/2944/15220890657_858528a186_o.png) - -You can also increment or decrement date or time by a number of days, weeks, months or years, and seconds, minutes or hours, respectively. You may combine date and time parameters in one command as well. - - # date --set='+5 minutes' - # date --set='-2 weeks' - # date --set='+3 months' - # date --set='-3 months +2 weeks -5 minutes' - -![](https://farm3.staticflickr.com/2943/15220655239_deba528dce_o.png) - -Finally, set the hardware clock to the current system time: - - # hwclock --systohc - -The purpose of running **hwclock --systohc** is to update the hardware clock with the software clock. This is to correct the systematic drift of the hardware clock, where it consistently gains or loses time at a certain rate. - -On the other hand, if the hardware clock shows correct date and time, but the system clock does not, the latter can be updated as follows: - - # hwclock --hctosys - -In either case, hwclock command synchronizes both clocks. Otherwise, the time will be wrong after the next reboot, since the hardware clock keeps the time when power is turned off. However, keep in mind that this is not applicable to virtual machines, as they cannot access the hardware clock of the host machine directly. - -If the default timezone is not correct on your Linux system, you can change it by following [this guideline][1]. - -### Method Two: NTP ### - -Another way to keep your system's date and time accurate is using NTP (network time protocol). On Linux, ntpdate command can synchronize system clock against [public NTP servers][2] using NTP. - -You can install **ntpdate** as follows: - -On Debian and derivatives: - - # aptitude install ntpdate - -On Red Hat-based distributions: - - # yum install ntpdate - -To synchronize system clock using NTP: - - # ntpdate -u - # hwclock --systohc - -![](https://farm4.staticflickr.com/3930/15404223021_8da3b44a62_z.jpg) - -As opposed to one-time clock sync using ntpdate, you can also set up NTP daemon (ntpd) on your system, so that ntpd always runs in the background, continuously adjusting system clock via NTP. Refer to [this guideline][3] to set up **ntpd**. - --------------------------------------------------------------------------------- - -via: http://ask.xmodulo.com/change-date-time-command-line-linux.html - -译者：[译者ID](https://github.com/译者ID) -校对：[wangjiezhe](https://github.com/wangjiezhe) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出 - -[1]:http://ask.xmodulo.com/change-timezone-linux.html -[2]:http://www.pool.ntp.org/ -[3]:http://xmodulo.com/how-to-synchronize-time-with-ntp.html diff --git a/translated/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md b/translated/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md new file mode 100644 index 0000000000..ffbce7a963 --- /dev/null +++ b/translated/tech/20141014 Linux FAQs with Answers--How to change date and time from the command line on Linux.md @@ -0,0 +1,84 @@ +Linux 有问必答 -- 在 Linux 上如何通过命令行来更改日期和时间 +================================================================================ +> **问题**: 在 Linux 上, 我怎样通过命令行来改变日期和时间? + +在 Linux 系统中保持日期和时间的同步是每一个 Linux 用户和系统管理员的重要责任. 很多程序都依靠精确的时间信息得以正常工作. 另外, 不精确的日期和时间会使得日志文件中的时间戳变得毫无意义, 减少了它们在系统检查和检修中的作用. 对于生产系统来说, 精确的日期和时间甚至更为重要. 例如, 在零售公司中, 所有产品必须时刻准确地计数(并储存在数据库服务器中)以便于财政部门计算每天及每周,每月,每年的支出和收入. + +我们必须注意, 在 Linux 机器上有两种时钟: 由内核维持的软件时钟(又称系统时钟)和在机器关机后记录时间的(电池驱动的)硬件时钟. 启动的时候, 内核会把系统时钟与硬件时钟同步. 之后, 两个时钟各自独立运行. + +### 方法一: Date 命令 ### + +在 Linux 中, 你可以通过 date 命令来更改系统的日期和时间: + + # date --set='NEW_DATE' + +其中 NEW_DATE 是诸如 "Sun, 28 Sep 2014 16:21:42" 或者 "2014-09-29 16:21:42" 的可读格式的日期字符串. + +日期格式也可以手动指定以获得更精确的结果: + + # date +FORMAT --set='NEW_DATE' + +例如: + + # date +’%Y%m%d %H%m’ --set='20140928 1518' + +![](https://farm3.staticflickr.com/2944/15220890657_858528a186_o.png) + +你也可以相对地增加或减少一定的天数,周数,月数和秒数,分钟数,小时数. 你也可以把日期和时间的参数放到一个命令中. + + # date --set='+5 minutes' + # date --set='-2 weeks' + # date --set='+3 months' + # date --set='-3 months +2 weeks -5 minutes' + +![](https://farm3.staticflickr.com/2943/15220655239_deba528dce_o.png) + +最后, 把硬件时钟设置为当前系统时钟: + + # hwclock --systohc + +运行 **hwclock --systohc** 的目的是将硬件时钟同软件时钟同步, 这可以更正硬件时钟的系统漂移(即时钟按照一定的速度走快或走慢). + +另一方面, 如果硬件时钟是正确的, 但系统时钟有误, 可以用下面的命令更正: + + # hwclock --hctosys + +在两种情况下, hwclock 命令都是将两个时钟同步. 否则, 重启后时间会是错误的, 因为当电源关闭时硬件时钟会记忆时间. 然而, 这对于虚拟机器并不适用, 因为虚拟机器并不能访问硬件时钟. + +如果你的 Linux 系统上的默认时区是错误的, 你可以按照[这个指导][1]进行更正. + +### 方法二: NTP ### + +另一种使系统日期和时间保持精确的方法是使用 NTP (网络时间协议). 在 Linux 上, ntpdate 命令通过 NTP 将系统时钟和[公共 NTP 服务器][2]同步. + +你可以使用如下命令来安装 **ntpdate**: + +在 Debian 及基于 Debian 的发行版上: + + # aptitude install ntpdate + +在基于 Ret Hat 的发行版上: + + # yum install ntpdate + +使用 NTP 同步系统时钟: + + # ntpdate -u + # hwclock --systohc + +![](https://farm4.staticflickr.com/3930/15404223021_8da3b44a62_z.jpg) + +除了一次性使用 ntpdate 来同步时钟, 你也可以使用 NTP 守护进程(ntpd), 它会始终在后台运行, 不断地通过 NTP 来调整系统时钟. 关于 NTP 的设置, 请参考[这个指导][3]. + +-------------------------------------------------------------------------------- + +via: http://ask.xmodulo.com/change-date-time-command-line-linux.html + +译者：[译者ID](https://github.com/译者ID) +校对：[wangjiezhe](https://github.com/wangjiezhe) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出 + +[1]:http://ask.xmodulo.com/change-timezone-linux.html +[2]:http://www.pool.ntp.org/ +[3]:http://xmodulo.com/how-to-synchronize-time-with-ntp.html