All about TIME in Linux

Below given are some useful commands pertaining to Time and Date:

[root@hostxyz ]# clock --show
Tue 08 Mar 2011 02:27:07 PM CST  -0.950788 seconds

[root@hostxyz ]# hwclock
Tue 08 Mar 2011 02:27:17 PM CST  -0.438789 seconds
[root@hostxyz ]#

Set the hardware clock by executing:

# /sbin/hwclock --systohc

Syncing the time with other or Internet Time servers:

# /usr/bin/rdate -s  <remote server ip/hostname>

Syncing the time with NTP server:

# ntpdate -u <NTP server IP/Hostname>

 
Use "time" command to find the time of execution of a command:

[root@hostxyz ]# time updatedb



real    0m13.759s



user    0m0.293s



sys     0m1.190s



[root@hostxyz ]# times updatedb



0m0.044s 0m0.029s



0m3.839s 0m1.830s



[root@hostxyz ]#

# Timezone config file

[root@hostxyz ]# cat /etc/sysconfig/clock
ZONE="America/Chicago"
UTC=true
ARC=false
[root@hostxyz ]#

If you wish the Change the Timezone to IST, follow the below steps:

# rm -rf  /etc/localtime

Change to the directory /usr/share/zoneinfo here you will find a list of time zone regions. Choose the most appropriate region, if you live in India in city Chennai, you will find a directory "Indian".

Create a symbolic link to the appropriate timezone to /etc/localtime. 

# ln -sf /usr/share/zoneinfo/Indian/Chennai /etc/localtime 
[root@hostxyz zoneinfo]# cat zone.tab | grep -w Indian
CC    -1210+09655       Indian/Cocos
CX    -1025+10543       Indian/Christmas
IO    -0720+07225       Indian/Chagos
KM    -1141+04316       Indian/Chennai
MG    -1855+04731       Indian/Antananarivo
MU    -2010+05730       Indian/Mauritius
MV    +0410+07330       Indian/Maldives
RE    -2052+05528       Indian/Reunion
SC    -0440+05528       Indian/Mahe
TF    -492110+0701303   Indian/Kerguelen
YT    -1247+04514       Indian/Mayotte

[root@hostxyz zoneinfo]#