Although VMware ESXi supports common Linux commands, its implementation is based on busybox. Some of the commands are not supported, or functionalities are reduced. Setting time is one of the cases.
To find out the current time, you issue the following command:
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~ # date Sun Jul 13 10:50:59 UTC 2014
Now if you want to use the same date command to change the time, it’s a different story. In fact, the help of the date command works as normal, but when you really type in full command, you’ll see it won’t work.
~ # date -s date: option requires an argument -- s BusyBox v1.19.0 (2012-02-29 14:20:08 PST) multi-call binary. Usage: date [OPTIONS] [+FMT] [TIME] Display time (using +FMT), or set time [-s,--set] TIME Set time to TIME -u,--utc Work in UTC (don't convert to local time) -R,--rfc-2822 Output RFC-2822 compliant date string -I[SPEC] Output ISO-8601 compliant date string SPEC='date' (default) for date only, 'hours', 'minutes', or 'seconds' for date and time to the indicated precision -r,--reference FILE Display last modification time of FILE -d,--date TIME Display TIME, not 'now' -D FMT Use FMT for -d TIME conversion Recognized TIME formats: hh:mm[:ss] [YYYY.]MM.DD-hh:mm[:ss] YYYY-MM-DD hh:mm[:ss] [[[[[YY]YY]MM]DD]hh]mm[.ss] ~ # date -s 2014-07-12 12:00:00 date: Setting date not supported; use <esxcli system time set>
Luckily, it gives hints on what command to use. To find the exact options, you can use –help to find out.
~ # esxcli system time set You must specify one of year, month, day, hour, minute or second ~ # esxcli system time set --help Usage: esxcli system time set [cmd options] Description: set Set the system clock time. Any missing parameters will default to the current time Cmd options: -d|--day=<long> Day -H|--hour=<long> Hour -m|--min=<long> Minute -M|--month=<long> Month -s|--sec=<long> Second -y|--year=<long> Year ~ # esxcli system time set -M 10 ~ # date Mon Oct 12 10:43:52 UTC 2014
With the esxcli command, you can also get the system time. Just change the set to get as follows:
~ # esxcli system time get 2014-07-12T10:59:14Z
Last, but not least, you should rely on the NTP server to sync up your server’s time in most of times. The only time you should use the change time is you don’t have NTP server, or you simply want to hack something in the ESXi server.