How to change date, time, timezone on centos 6

Display Date and Time in Linux

1

# date

and its output

1	Sat Mar 15 03:14:29 PDT 2014

Change Timezone in Linux

Fist, we are going to get a list of timezone that came with Linux.

1	# cd /usr/share/zoneinfo/ # ls

1 2 3 4 5 6 7 8 9 10

Africa      Canada   GB         Indian     Mexico    ROK        iso3166.tab America     Chile    GB–Eire    Iran       NZ        Singapore  posix Antarctica  Cuba     GMT        Israel     NZ–CHAT   Turkey     posixrules Arctic      EET      GMT+0      Jamaica    Navajo    UCT        right Asia        EST      GMT–0      Japan      PRC       US         zone.tab Atlantic    EST5EDT  GMT0       Kwajalein  PST8PDT   UTC Australia   Egypt    Greenwich  Libya      Pacific   Universal Brazil      Eire     HST        MET        Poland    W–SU CET         Etc      Hongkong   MST        Portugal  WET CST6CDT     Europe   Iceland    MST7MDT    ROC       Zulu

There are countries, or continent with different timezone, for example when you list all file and directories in zoneinfo directory as I did above, there are timezone for countries with only one timezone, and directories for countries and continent with several timezones. For example my timezone is America Pacific, I will need to go to America directory to get my timezone.

1 2	# cd /usr/share/zoneinfo/Asia/ # ls

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

Aden        Chungking    Kabul         Novokuznetsk   Tashkent Almaty      Colombo      Kamchatka     Novosibirsk    Tbilisi Amman       Dacca        Karachi       Omsk           Tehran Anadyr      Damascus     Kashgar       Oral           Tel_Aviv Aqtau       Dhaka        Kathmandu     Phnom_Penh     Thimbu Aqtobe      Dili         Katmandu      Pontianak      Thimphu Ashgabat    Dubai        Khandyga      Pyongyang      Tokyo Ashkhabad   Dushanbe     Kolkata       Qatar          Ujung_Pandang Baghdad     Gaza         Krasnoyarsk   Qyzylorda      Ulaanbaatar Bahrain     Harbin       Kuala_Lumpur  Rangoon        Ulan_Bator Baku        Hebron       Kuching       Riyadh         Urumqi Bangkok     Ho_Chi_Minh  Kuwait        Saigon         Ust-Nera Beirut      Hong_Kong    Macao         Sakhalin       Vientiane Bishkek     Hovd         Macau         Samarkand      Vladivostok Brunei      Irkutsk      Magadan       Seoul          Yakutsk Calcutta    Istanbul     Makassar      Shanghai       Yekaterinburg Chita       Jakarta      Manila        Singapore      Yerevan Choibalsan  Jayapura     Muscat        Srednekolymsk Chongqing   Jerusalem    Nicosia       Taipei

I will use Toronto for Pacific time, so I will need to copy/set Toronto file as my localtime on my server (this will work with any linux system I believe).

1	# cp /usr/share/zoneinfo/Asia/Ho_Chi_Minh /etc/localtime

Change Date and Time in Linux

Now your Linux system should have the timezone that you want. If the date or time is not correct, you can set date and time with date command.

1	# date MMDDhhmmYYYY

• MM: two digit month number
• DD: two digit date
• hh: two digit hour (24 hour system)
• mm: two digit minute
• YYYY: four digit of year

You can also sync your system time and date with ntp (Network Time Protocol) over a network or internet. Normally ntp should be installed to your Linux system as default, in case your system does not have ntp, you can easily install ntp package with a simple command.

To install ntp on Ubuntu, Linux or debian based distribitions

1 2	# apt-get update # apt-get install ntp

To install ntp on Fedora, Centos or redhat based distribitions

1	# yum install ntp

After you set your timezone correcly, you should be able to synce your date and time with ntp command

1	# ntpdate pool.ntp.org

Note: if you have a VPS (virtual private server) and not a real dedicated server, you will properly won’t be able to adjust time on your VPS. When you are on VPS, you do not have the right to modify or update time and date, only the VPS owner or provider have the rights to adjust time and date on that VPS node.

Recover the SUSE Linux root password

1. Boot server from the installation CD.
2. Then select “Rescue System”
3. Login as root
4. Type
   fdisk -l

   to list the partitions. Locate the Linux root partition

CASE 1 – root partition is not LVM filesystem

mount /dev/sda2 /mnt
(replace sda2 with the device name for the Linux root partition identified in your system).

mount –bind /dev /mnt/dev
to make the device files available (this is needed for access to the urandom device which may be used by thepasswd command below).

chroot /mnt /bin/bash

passwd root

and reset the root password.

CASE 2 – root partition is LVM filesystem

# lvm vgscan -v

Activate all volume groups:
# lvm vgchange -a y

List logical volumes:
# lvm lvs –all

With this information, and the volumes activated, you should be able to mount the volumes:
# mount /dev/mapper/yourfilesystem  /mnt

mount –bind /dev /mnt/dev
to make the device files available (this is needed for access to the urandom device which may be used by thepasswd command below).

chroot /mnt /bin/bash

passwd root

and reset the root password.