The Code & Revolution OS! Documentary films on Linux released in 2001.
Documentary films on Linux
Yup, you read it right. The Code & Revolution OS! Those are documentary films released in 2001. The Code is based on birth and journey of Linux & Revolution OS is based on 20 years journey of Linux, GNU, Open Source world.
Have you watched them?
The Code (Wiki Page) is a 58-minute documentary featuring the creator of Linux, Linus Torvalds, and some of the programmers who contributed to Linux. And yeah, there is a piece of the interview where Linus talks about developers of India! Since I am from India, I feel like mentioning it here 🙂
Revolution OS is (Wiki Page) is 85 minutes long documentary which spans over 20 years journey of free software movement through Linux, GNU, and Open Source.
Documentary films are available on YouTube along with subtitles.
Learn how to remount the file system in the read-write mode under Linux. The article also explains how to check if the file system is read-only and how to clean the file system
Re-mount filesystem as read-write
Most of the time on newly created file systems of NFS filesystems we see an error like below :
This is because the file system is mounted as read-only. In such a scenario you have to mount it in read-write mode. Before that, we will see how to check if the file system is mounted in read-only mode and then we will get to how to remount it as a read-write filesystem.
How to check if file system is read only
To confirm file system is mounted in read only mode use below command –
Grep your mount point in cat /proc/mounts and observer third column which shows all options which are used in the mounted file system. Here ro denotes file system is mounted read-only.
You can also get these details using mount -v command
root@kerneltalks # mount -v |grep datastore
/dev/xvdf on /datastore type ext3 (ro,relatime,seclabel,data=ordered)
In this output. file system options are listed in braces at last column.
Re-mount file system in read-write mode
To remount file system in read-write mode use below command –
root@kerneltalks # mount -o remount,rw /datastore
root@kerneltalks # mount -v |grep datastore
/dev/xvdf on /datastore type ext3 (rw,relatime,seclabel,data=ordered)
Observe after re-mounting option ro changed to rw. Now, the file system is mounted as read-write and now you can write files in it.
Note : It is recommended to fsck file system before re mounting it.
You can check file system by running fsck on its volume.
Sometimes there are some corrections that need to be made on a file system that needs a reboot to make sure there are no processes are accessing the file system.
Learn how to list YUM repositories in RHEL / CentOS. This how-to guide includes various commands along with examples to check details about repositories and their packages in Red Hat systems.
Listing YUM repo in Red Hat systems
YUM (Yellow dog Updater Modified) is a package management tool in Red Hat Linux and its variants like CentOS. In this article, we will walk you through several commands which will be useful for you to get details of YUM repositories in RHEL.
Without any further delay, let’s see a list of commands and their example outputs.
List YUM repositories
Run command yum repolist and it will show you all repositories configured under YUM and enabled for use on that server. To view, disabled repositories or all repositories refer below section in this article.
[root@kerneltalks ~]# yum repolist
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
repo id repo name status
*epel/x86_64 Extra Packages for Enterprise Linux 6 - x86_64 12,448
rhui-REGION-client-config-server-7/x86_64 Red Hat Update Infrastructure 2.0 Client Configuration Server 7 2
rhui-REGION-rhel-server-releases/7Server/x86_64 Red Hat Enterprise Linux Server 7 (RPMs) 17,881
rhui-REGION-rhel-server-rh-common/7Server/x86_64 Red Hat Enterprise Linux Server 7 RH Common (RPMs) 231
rsawaroha rsaw aroha rpms for Fedora/RHEL6+ 19
repolist: 30,581
In the above output, you can see the repo list with repo id, repo name, and status. You can see we have EPEL repo configured (repo id epel/x86_64) on the server. Also, last repo rsawaroha we added for installation of xsos tool used to read sosreport.
What is the status column in yum repolist ?
Last column of yum repolist output is status which has numbers in it. You might be wondering, what is the meaning of status numbers in yum repolist?
They are a number of packages included in the respective repository! If you see a number like XXXX+N i.e. followed by + sign and another number then it means that the repository has XXXX number of packages available for installation and N number of packages are excluded.
List details of YUM repositories
Each repositories details like name, id, number of packages available, total size, link details, timestamps, etc can be viewed by using verbose mode. Use -v switch with yum repolist to view repositories details.
[root@kerneltalks ~]# yum -v repolist
Not loading "rhnplugin" plugin, as it is disabled
Loading "amazon-id" plugin
Not loading "product-id" plugin, as it is disabled
Loading "rhui-lb" plugin
Loading "search-disabled-repos" plugin
Not loading "subscription-manager" plugin, as it is disabled
Config time: 0.048
Yum version: 3.4.3
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/supplementary/os
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/extras/os
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/rh-common/debug
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/supplementary/debug
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/rhscl/1/debug
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/rhui-client-config/rhel/server/7/x86_64/os
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/rhscl/1/source/SRPMS
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/rhscl/1/os
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/source/SRPMS
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/extras/debug
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/optional/source/SRPMS
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/optional/debug
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/supplementary/source/SRPMS
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/debug
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/optional/os
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/extras/source/SRPMS
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/rh-common/os
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/rh-common/source/SRPMS
mirrorlist: https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/os
Setting up Package Sacks
pkgsack time: 0.009
Repo-id : epel/x86_64
Repo-name : Extra Packages for Enterprise Linux 6 - x86_64
Repo-revision: 1515267354
Repo-updated : Sat Jan 6 19:58:06 2018
Repo-pkgs : 12,448
Repo-size : 11 G
Repo-metalink: https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=x86_64
Updated : Mon Jan 8 15:45:02 2018
Repo-baseurl : http://mirror.sjc02.svwh.net/fedora-epel/6/x86_64/ (43 more)
Repo-expire : 21,600 second(s) (last: Mon Jan 8 19:23:12 2018)
Filter : read-only:present
Repo-filename: /etc/yum.repos.d/epel.repo
Repo-id : rhui-REGION-client-config-server-7/x86_64
Repo-name : Red Hat Update Infrastructure 2.0 Client Configuration Server 7
Repo-revision: 1509723523
Repo-updated : Fri Nov 3 15:38:43 2017
Repo-pkgs : 2
Repo-size : 106 k
Repo-mirrors : https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/rhui-client-config/rhel/server/7/x86_64/os
Repo-baseurl : https://rhui2-cds02.ap-south-1.aws.ce.redhat.com/pulp/repos//rhui-client-config/rhel/server/7/x86_64/os/ (1 more)
Repo-expire : 21,600 second(s) (last: Mon Jan 8 19:23:13 2018)
Filter : read-only:present
Repo-filename: /etc/yum.repos.d/redhat-rhui-client-config.repo
Repo-id : rhui-REGION-rhel-server-releases/7Server/x86_64
Repo-name : Red Hat Enterprise Linux Server 7 (RPMs)
Repo-revision: 1515106250
Repo-updated : Thu Jan 4 22:50:49 2018
Repo-pkgs : 17,881
Repo-size : 24 G
Repo-mirrors : https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/os
Repo-baseurl : https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/repos//content/dist/rhel/rhui/server/7/7Server/x86_64/os/ (1 more)
Repo-expire : 21,600 second(s) (last: Mon Jan 8 19:23:13 2018)
Filter : read-only:present
Repo-filename: /etc/yum.repos.d/redhat-rhui.repo
Repo-id : rhui-REGION-rhel-server-rh-common/7Server/x86_64
Repo-name : Red Hat Enterprise Linux Server 7 RH Common (RPMs)
Repo-revision: 1513002956
Repo-updated : Mon Dec 11 14:35:56 2017
Repo-pkgs : 231
Repo-size : 4.5 G
Repo-mirrors : https://rhui2-cds01.ap-south-1.aws.ce.redhat.com/pulp/mirror/content/dist/rhel/rhui/server/7/7Server/x86_64/rh-common/os
Repo-baseurl : https://rhui2-cds02.ap-south-1.aws.ce.redhat.com/pulp/repos//content/dist/rhel/rhui/server/7/7Server/x86_64/rh-common/os/ (1 more)
Repo-expire : 21,600 second(s) (last: Mon Jan 8 19:23:13 2018)
Filter : read-only:present
Repo-filename: /etc/yum.repos.d/redhat-rhui.repo
Repo-id : rsawaroha
Repo-name : rsaw aroha rpms for Fedora/RHEL6+
Repo-revision: 1507778106
Repo-updated : Thu Oct 12 03:15:06 2017
Repo-pkgs : 19
Repo-size : 1.4 M
Repo-baseurl : http://people.redhat.com/rsawhill/rpms
Repo-expire : 21,600 second(s) (last: Mon Jan 8 18:02:10 2018)
Filter : read-only:present
Repo-filename: /etc/yum.repos.d/rsawaroha.repo
repolist: 30,581
List enabled YUM repositories
Under YUM you have the choice to enable or disable repositories. During yum operations like installation of packages only enabled repositories are scanned/contacted to perform operations.
To view only enabled repositories in YUM, use yum repolist enabled
[root@kerneltalks ~]# yum repolist enabled
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
repo id repo name status
*epel/x86_64 Extra Packages for Enterprise Linux 6 - x86_64 12,448
rhui-REGION-client-config-server-7/x86_64 Red Hat Update Infrastructure 2.0 Client Configuration Server 7 2
rhui-REGION-rhel-server-releases/7Server/x86_64 Red Hat Enterprise Linux Server 7 (RPMs) 17,881
rhui-REGION-rhel-server-rh-common/7Server/x86_64 Red Hat Enterprise Linux Server 7 RH Common (RPMs) 231
rsawaroha rsaw aroha rpms for Fedora/RHEL6+ 19
repolist: 30,581
List disabled YUM repositories
Similarly, you can list only disabled yum repositories as well. Use yum repolist disabled
[root@kerneltalks ~]# yum repolist disabled
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
repo id repo name
epel-debuginfo/x86_64 Extra Packages for Enterprise Linux 6 - x86_64 - Debug
epel-source/x86_64 Extra Packages for Enterprise Linux 6 - x86_64 - Source
epel-testing/x86_64 Extra Packages for Enterprise Linux 6 - Testing - x86_64
epel-testing-debuginfo/x86_64 Extra Packages for Enterprise Linux 6 - Testing - x86_64 - Debug
epel-testing-source/x86_64 Extra Packages for Enterprise Linux 6 - Testing - x86_64 - Source
rhui-REGION-rhel-server-debug-extras/7Server/x86_64 Red Hat Enterprise Linux Server 7 Extra Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-optional/7Server/x86_64 Red Hat Enterprise Linux Server 7 Optional Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-rh-common/7Server/x86_64 Red Hat Enterprise Linux Server 7 RH Common Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-rhscl/7Server/x86_64 Red Hat Enterprise Linux Server 7 RHSCL Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-supplementary/7Server/x86_64 Red Hat Enterprise Linux Server 7 Supplementary Debug (Debug RPMs)
rhui-REGION-rhel-server-extras/7Server/x86_64 Red Hat Enterprise Linux Server 7 Extra(RPMs)
rhui-REGION-rhel-server-optional/7Server/x86_64 Red Hat Enterprise Linux Server 7 Optional (RPMs)
rhui-REGION-rhel-server-releases-debug/7Server/x86_64 Red Hat Enterprise Linux Server 7 Debug (Debug RPMs)
rhui-REGION-rhel-server-releases-source/7Server/x86_64 Red Hat Enterprise Linux Server 7 (SRPMs)
rhui-REGION-rhel-server-rhscl/7Server/x86_64 Red Hat Enterprise Linux Server 7 RHSCL (RPMs)
rhui-REGION-rhel-server-source-extras/7Server/x86_64 Red Hat Enterprise Linux Server 7 Extra (SRPMs)
rhui-REGION-rhel-server-source-optional/7Server/x86_64 Red Hat Enterprise Linux Server 7 Optional (SRPMs)
rhui-REGION-rhel-server-source-rh-common/7Server/x86_64 Red Hat Enterprise Linux Server 7 RH Common (SRPMs)
rhui-REGION-rhel-server-source-rhscl/7Server/x86_64 Red Hat Enterprise Linux Server 7 RHSCL (SRPMs)
rhui-REGION-rhel-server-source-supplementary/7Server/x86_64 Red Hat Enterprise Linux Server 7 Supplementary (SRPMs)
rhui-REGION-rhel-server-supplementary/7Server/x86_64 Red Hat Enterprise Linux Server 7 Supplementary (RPMs)
repolist: 0
List all configured YUM repositories
List all YUM repositories available on server.
[root@kerneltalks ~]# yum repolist all
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
repo id repo name status
*epel/x86_64 Extra Packages for Enterprise Linux 6 - x86_64 enabled: 12,448
epel-debuginfo/x86_64 Extra Packages for Enterprise Linux 6 - x86_64 - Debug disabled
epel-source/x86_64 Extra Packages for Enterprise Linux 6 - x86_64 - Source disabled
epel-testing/x86_64 Extra Packages for Enterprise Linux 6 - Testing - x86_64 disabled
epel-testing-debuginfo/x86_64 Extra Packages for Enterprise Linux 6 - Testing - x86_64 - Debug disabled
epel-testing-source/x86_64 Extra Packages for Enterprise Linux 6 - Testing - x86_64 - Source disabled
rhui-REGION-client-config-server-7/x86_64 Red Hat Update Infrastructure 2.0 Client Configuration Server 7 enabled: 2
rhui-REGION-rhel-server-debug-extras/7Server/x86_64 Red Hat Enterprise Linux Server 7 Extra Debug (Debug RPMs) disabled
rhui-REGION-rhel-server-debug-optional/7Server/x86_64 Red Hat Enterprise Linux Server 7 Optional Debug (Debug RPMs) disabled
rhui-REGION-rhel-server-debug-rh-common/7Server/x86_64 Red Hat Enterprise Linux Server 7 RH Common Debug (Debug RPMs) disabled
rhui-REGION-rhel-server-debug-rhscl/7Server/x86_64 Red Hat Enterprise Linux Server 7 RHSCL Debug (Debug RPMs) disabled
rhui-REGION-rhel-server-debug-supplementary/7Server/x86_64 Red Hat Enterprise Linux Server 7 Supplementary Debug (Debug RPMs) disabled
rhui-REGION-rhel-server-extras/7Server/x86_64 Red Hat Enterprise Linux Server 7 Extra(RPMs) disabled
rhui-REGION-rhel-server-optional/7Server/x86_64 Red Hat Enterprise Linux Server 7 Optional (RPMs) disabled
rhui-REGION-rhel-server-releases/7Server/x86_64 Red Hat Enterprise Linux Server 7 (RPMs) enabled: 17,881
rhui-REGION-rhel-server-releases-debug/7Server/x86_64 Red Hat Enterprise Linux Server 7 Debug (Debug RPMs) disabled
rhui-REGION-rhel-server-releases-source/7Server/x86_64 Red Hat Enterprise Linux Server 7 (SRPMs) disabled
rhui-REGION-rhel-server-rh-common/7Server/x86_64 Red Hat Enterprise Linux Server 7 RH Common (RPMs) enabled: 231
rhui-REGION-rhel-server-rhscl/7Server/x86_64 Red Hat Enterprise Linux Server 7 RHSCL (RPMs) disabled
rhui-REGION-rhel-server-source-extras/7Server/x86_64 Red Hat Enterprise Linux Server 7 Extra (SRPMs) disabled
rhui-REGION-rhel-server-source-optional/7Server/x86_64 Red Hat Enterprise Linux Server 7 Optional (SRPMs) disabled
rhui-REGION-rhel-server-source-rh-common/7Server/x86_64 Red Hat Enterprise Linux Server 7 RH Common (SRPMs) disabled
rhui-REGION-rhel-server-source-rhscl/7Server/x86_64 Red Hat Enterprise Linux Server 7 RHSCL (SRPMs) disabled
rhui-REGION-rhel-server-source-supplementary/7Server/x86_64 Red Hat Enterprise Linux Server 7 Supplementary (SRPMs) disabled
rhui-REGION-rhel-server-supplementary/7Server/x86_64 Red Hat Enterprise Linux Server 7 Supplementary (RPMs) disabled
rsawaroha rsaw aroha rpms for Fedora/RHEL6+ enabled: 19
repolist: 30,581
List all available packages in repositories
To list all available packages for installation from all repositories use below command –
yum list available command is useful to list all available packages. If you want to list packages from the particular repository then use below switches –
disablerepo="*" which will exclude all repos from scanning
enablerepo="<repo>" which will include only your desired repo to scan for packages.
Learn how to use xsos tool to read sosreport in RHEL/CentOS. xsos is a very helpful tool for Linux sysadmins. Different options and their examples included in the article.
xsos tool to read sosreport
an xsos tool is a tool coded to read a sosreport on Linux systems. sosreport is a tool from RedHat which collects system information which helps vendors to troubleshoot issues. sosreportcreates the tarball which contains all the system information but you can not read it directly. For simplicity, Ryan Sawhill created a tool named xsos which will help you to read sosreport in a much easier way in your terminal itself. In this article, we will walk you through how to read sosreport on the Linux terminal.
Now there are different switches you can use with xsos command and get the required details. Frequently used switches given below –
-a show everything
-b show info from dmidecode
-o show hostname, distro, SELinux, kernel info, uptime, etc
-k inspect kdump configuration
-c show info from /proc/cpuinfo
-m show info from /proc/meminfo
-d show info from /proc/partitions
-t show info from dm-multipath
-i show info from ip addr
Above is a snippet from help. Full list of switches can be obtained by running help using xsos -h
Reading sosreport using xsos
To read sosreport using xsos tool, you need to first extract sosreport tarball and use the extracted directory path as a source for the xsos tool. The command format is –
xsos –<switch> <sosreport_dir_path>
For example, lets see CPU information read from sosreport.
root@kerneltalks # xsos -c /var/tmp/sosreport-kerneltalks-20180108180100
CPU
1 logical processors
1 Intel Xeon CPU E5-2676 v3 @ 2.40GHz (flags: aes,constant_tsc,ht,lm,nx,pae,rdrand)
Here, -c instructs xsos command to read CPU information from sosreport which is saved in /var/tmp/sosreport-kerneltalks-20180108180100 directory.
Another example below which reads IP information from sosreport.
root@kerneltalks # xsos -i /var/tmp/sosreport-kerneltalks-20180108180100
IP4
Interface Master IF MAC Address MTU State IPv4 Address
========= ========= ================= ====== ===== ==================
lo - - 65536 up 127.0.0.1/8
eth0 - 02:e5:4c:f8:86:0e 9001 up 172.31.29.189/20
IP6
Interface Master IF MAC Address MTU State IPv6 Address Scope
========= ========= ================= ====== ===== =========================================== =====
lo - - 65536 up ::1/128 host
eth0 - 02:e5:4c:f8:86:0e 9001 up fe80::e5:4cff:fef8:860e/64 link
you can see IP information fetched from stored sosreport and displayed for your understanding.
You can use different switches to fetch different information as per your requirement from the sosreport. This way you need not go through each and every logfile or log directory extracted in the sosreport directory to get the information. Just use a relevant switch with xsos utility and it will scan the sosreport directory and present your data!
Troubleshooting guide to reclaim space on disk after deleting files in Linux.
Space is not released after deleting files in Linux? Read this troubleshooting guide
One of the common issues Linux Unix system users face is disk space is not being released even after files are deleted. Sysadmins face some issues when they try to recover disk space by deleting high sized files in a mount point and then they found disk utilization stays the same even after deleting huge files. Sometimes, application users are moving/deleting large log files and still won’t be able to reclaim space on the mount point.
In this troubleshooting guide, I will walk you through steps that will help you to reclaim space on disk after deleting files. Here we will learn how to remove deleted open files in Linux. Most of the time files are deleted manually but processes using those files keep them open and hence space is not reclaimed. df also shows incorrect space utilization.
Process stop/start/restart
To resolve this issue, you need to gracefully or forcefully end processes using those deleted files. First, get a list of such deleted files that are still marked open by processes. Use lsof (list open files) command with +L1 switch for this or you can directly grep for deleted in lsof output without switch
Now, in above output check the PID 777and stop that process. If you can not stop it you can kill the process. In the case of application processes, you can refer application guides on how to stop, start, restart its processes. The restarting process helps in releasing the lock on that file which process made to hold it as open. Once the related process is stopped/restarted you can see space will be released and you can observe reduced utilization in df command output.
Clear from proc filesystem
Another way is to vacate the space used by file by de-allocating that space from /proc filesystem. As you are aware, every process in Linux has its allocations in /proc filesystem i.e. process filesystem. Make sure that the process/application has no impact if you are flushing files (which are held open by an app) from /proc filesystem.
You can find file allocation at /proc/<pid>/fd/<fd_number> location. Where PID and fd_number you can get from lsof output we saw above. If you check the type of this file then it’s a symbolic link to your deleted file.
root@kerneltalks # file /proc/777/fd/7
/proc/777/fd/7: broken symbolic link to `/tmp/ffiJEo5nz (deleted)
So, in our case we can do it using –
root@kerneltalks # > /proc/777/fd/7
That’s it! Flushing it will regain your lost space by those files which you already deleted.
An article explaining step by step procedure to add EBS disk on AWS Linux server with screenshots.
EBS disk addition on AWS instance
Nowadays most of the servers run on cloud platforms like Amazon Web Services (AWS), Azure, etc. So daily administrative tasks on Linux servers from AWS console is one of the common things in sysadmin’s task list. In this article, we will walk you through one such task i.e. adding a new disk to the AWS Linux server.
Adding a disk to the EC2 Linux server has two portions. The first portion is to be done on AWS EC2 console which is creating new volume to be attached to the server. And attaching it to EC2 instance on AWS console. The second portion is to be done on the Linux server which is to identify newly added disk at the kernel level and prepare it for use.
Creating & attaching EBS volume
In this step, we will learn how to create EBS volume in the AWS console and how to attach EBS volume to AWS EC2 instance.
Login to your EC2 console and navigate to Volumes which is under ELASTIC BLOCK STORAGE menu on the left-hand sidebar. You will be presented with the current list of volumes in your AWS account like below –
Create volume in AWS
Now, click Create Volume button and you will be presented with the below screen.
Volume creation in AWS
Here you need to choose several parameters of your volume –
Volume Type. This decides your volume performance and obv billing.
Size. In GB. Min and Max available sizes differ according to your volume type choice.
IOPS. Performance parameters. Changes according to your volume type choice
Availability Zone. Make sure you select same AZ as your EC2 instance
Throughput. Performance parameter. Only available for ST1 & SC1 volume type.
Snapshot ID. Select snapshot if you want to create the new volume from existing snapshot backup. For fresh blank volume leave it blank.
Encryption. Checkmark if you want the volume to be encrypted. An extra layer of security.
Tags. Add tags for management, reporting, billing purposes.
After selecting proper parameters as per your requirement, click Create Volume button. You will be presented with ‘Volume created successfully’ dialogue if everything goes well along with the volume ID of your newly created volume. Click Close and you will be back of the volume list.
Now check volume ID to identify your newly created volume in this list. It will be marked with an ‘Available’ state. Select that volume and select Attach volume from Actions menu.
Attach volume menu
Now you will be presented with an instance selection menu. Here you need to choose an instance to which this volume is to be attached. Remember only instances in the same AZ of the volume are
Attach volume instance selection
Once you select the instance you can see the device name which will be reflected at the kernel level in your instance under Device field. Here its /dev/sdf.
Check out the note being displayed here. It says : Note: Newer Linux kernels may rename your devices to /dev/xvdf through /dev/xvdp internally, even when the device name entered here (and shown in the details) is /dev/sdf through /dev/sdp.
It says newer Linux kernels may interpret your device name as /dev/xvdf than /dev/sdf. This means this volume will be either /dev/sdf (on the old kernel) or /dev/xvdf on the new kernel.
That’s it. Once attached you can see volume state is changed from Available to in-use
Identifying volume on Linux instance
Now head back to your Linux server. Log in and check new volume in fdisk -l output.
root@kerneltalks # fdisk -l
WARNING: fdisk GPT support is currently new, and therefore in an experimental ph ase. Use at your own discretion.
Disk /dev/xvda: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: gpt
Disk identifier: 25D08425-708A-47D2-B907-1F0A3F769A90
# Start End Size Type Name
1 2048 4095 1M BIOS boot parti
2 4096 20971486 10G Microsoft basic
Disk /dev/xvdf: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
As AWS mentioned new device name will be reflected as /dev/xvdf in the kernel, you can see /dev/xvdf in the above output.
Now you need to partition this disk using LVM (using pvcreate) or fdisk so that you can use it for creating mount points!
Learn xfs file system commands to create, grow, repair xfs file system along with command examples.
Learn xfs commands with examples
In our other article, we walked you through what is xfs, features of xfs, etc. In this article, we will see some frequently used xfs administrative commands. We will see how to create xfs filesystem, how to grow xfs filesystem, how to repair the xfs file system, and check xfs filesystem along with command examples.
Create XFS filesystem
mkfs.xfs command is used to create xfs filesystem. Without any special switches, command output looks like one below –
Note: Once the XFS filesystem is created it can not be reduced. It can only be extended to a bigger size.
Resize XFS file system
In XFS, you can only extend the file system and can not reduce it. To grow XFS file system use xfs_growfs. You need to specify a new size of mount point along with -D switch. -D takes argument number as file system blocks. If you don’t supply -D switch, xfs_growfs will grow the filesystem to the maximum available limit on that device.
In the above output, observe the last line. Since I supplied a new size smaller than the existing size, xfs_growfs didn’t change the filesystem. This shows you can not reduce the XFS file system. You can only extend it.
Now, I supplied new size 1 GB extra and it successfully grew the file system.
1 GB blocks calculation :
The current filesystem has bsize=4096 i.e. block size of 4MB. We need 1 GB i.e. 256 blocks. So add 256 in a current number of blocks i.e. 2883584 which gives you 2883840. So I used 2883840 as an argument to -D switch.
Repair XFS file system
File system consistency check and repair of XFS can be performed using xfs_repair command. You can run the command with -n switch so that it will not modify anything on the filesystem. It will only scans and reports which modifications to be done. If you are running it without -n switch, it will modify the file system wherever necessary to make it clean.
Please note that you need to un-mount the XFS filesystem before you can run checks on it. Otherwise, you will see the below error.
root@kerneltalks # xfs_repair -n /dev/xvdf
xfs_repair: /dev/xvdf contains a mounted filesystem
xfs_repair: /dev/xvdf contains a mounted and writable filesystem
fatal error -- couldn't initialize XFS library
Once successfully un-mounting file system you can run command on it.
root@kerneltalks # xfs_repair -n /dev/xvdf
Phase 1 - find and verify superblock...
Phase 2 - using internal log
- zero log...
- scan filesystem freespace and inode maps...
- found root inode chunk
Phase 3 - for each AG...
- scan (but don't clear) agi unlinked lists...
- process known inodes and perform inode discovery...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- agno = 4
- process newly discovered inodes...
Phase 4 - check for duplicate blocks...
- setting up duplicate extent list...
- check for inodes claiming duplicate blocks...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- agno = 4
No modify flag set, skipping phase 5
Phase 6 - check inode connectivity...
- traversing filesystem ...
- traversal finished ...
- moving disconnected inodes to lost+found ...
Phase 7 - verify link counts...
No modify flag set, skipping filesystem flush and exiting.
In the above output you can observe, in each phase command shows possible modification which can be done to make the file system healthy. If you want the command to do that modification during the scan then run the command without any switch.
root@kerneltalks # xfs_repair /dev/xvdf
Phase 1 - find and verify superblock...
Phase 2 - using internal log
- zero log...
- scan filesystem freespace and inode maps...
- found root inode chunk
Phase 3 - for each AG...
- scan and clear agi unlinked lists...
- process known inodes and perform inode discovery...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- agno = 4
- process newly discovered inodes...
Phase 4 - check for duplicate blocks...
- setting up duplicate extent list...
- check for inodes claiming duplicate blocks...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- agno = 4
Phase 5 - rebuild AG headers and trees...
- reset superblock...
Phase 6 - check inode connectivity...
- resetting contents of realtime bitmap and summary inodes
- traversing filesystem ...
- traversal finished ...
- moving disconnected inodes to lost+found ...
Phase 7 - verify and correct link counts...
done
In the above output, you can observer xfs_repair command is executing possible filesystem modification as well to make it healthy.
Check XFS version and details
Checking the xfs file system requires it to un-mount. Run xfs_db command on its device path and once you entered xfs_db prompt, run version command.
xfs_db command normally used for examining the XFS file system. version command used to enable features in the file system. Without any argument, the current version and feature bits are printed
To view details of the XFS file system like block size and number of blocks which helps you in calculating new block number for growing XFS file system, use xfs_info without any switch.
Learn timezone management using timedatectl command. An article explaining different uses of timedatectl command along with examples.
Learn timedatectl command
In our previous article, we have seen how to change the timezone of the Linux server using files or variables in the system. Few of our readers pushed timedatectl command to achieve this task easily. So I thought of writing a separate article on timedatectl command explaining all its usage.
In this article, we will see how to display server time details, view, list, and change the timezone of the server using timedatectl command. If you want to use date or time in a shell script or as a variable, we explained here how to format the date and time to use it as variable or in scripting.
timedatectl is Time Date Control command! It used to control the date and time of the server in Linux. To check your current system date and time details, run this command without any switch –
root@kerneltalks # timedatectl
Local time: Wed 2017-11-15 15:58:33 UTC
Universal time: Wed 2017-11-15 15:58:33 UTC
RTC time: Wed 2017-11-15 15:58:32
Time zone: UTC (UTC, +0000)
NTP enabled: yes
NTP synchronized: yes
RTC in local TZ: no
DST active: n/a
Where,
Local time : Your system’s local date and time
Universal time : Current UTC time
RTC time : Current Real-time clock time
Time zone : Your system’s current timezone
NTP enabled : Is NTP is enabled on system or not
NTP synchronized : NTP time synced or not.
RTC in local TZ : Is RTC maintaining in configured system TZ? It is recommended to keep it off.
DST active : Daylight saving time enabled or not
List and change timezone using timedatectl
timedatectl allow you to change the timezone of the system with a list of available timezones. To view, a list of available timezones use the command with list-timezones switch.
You will be presented with a list of available timezones in a paged manner. You can use any of thee timezones to set on your local system. To change timezone of your system use set-timezone switch.
Above command will change server timezone to Australia/Sydney one.
Change date and time using timedatectl
Most of the servers are configured with NTP these days. But if not and/or if you want to change the date and time manually then you can use set-time switch. Time should be supplied with YYYY-MM-DD HH:MM:SS
If NTP is configured then you might see an error Failed to set time: Automatic time synchronization is enabled when attempting to change system time manually.
Enable/Disable RTC and NTP using timedatectl
You can enable or disable RTC (Real Time Clock) and NTP using timedatectl. For RTC use set-local-rtc and for NTP use set-ntp switch. Both arguments accepts 1 (to enable) and 0 (to disable) as values.
Please note that enabling NTP here does not take you through NTP configuration steps. That has to be done separately. This only controls if the system should sync time using configured NTP or not.
Manage date and time of other machine
You can use timedatectl command to manage the date and time of local containers or remote machines. To manage the time of local container use -M switch whereas to connect to the remote host and manage its time use -H switch.
-M switch takes argument as --host=ip/hostname. -H switch takes argument as --machine=container_name.
That’s all switches which are mainly useful in day-to-day operations. There are a few more that can be referred from its man page.
Learn how to troubleshoot RPC: Port mapper failure – Timed out error on NFS client. This will help you to resolve NFS mounting being timed out issue.
RPC: Port mapper failure – Timed out
In this article, we are going to discuss the troubleshooting of one of the NFS errors you see on NFS clients. This error can be seen while trying commands related to NFS like below :
root@kerneltalks # showmount -e mynfsserver
clnt_create: RPC: Port mapper failure - Timed out
root@kerneltalks # rpcinfo -p mynfsserver
mynfsserver: RPC: Port mapper failure - Timed out
Normally when you see this error you are not able to mount NFS share as well. You will see mount.nfs: Connection timed out error when you try to mount NFS share.
root@kerneltalks # mount mynfsserver:/data /nfs_data
mount.nfs: Connection timed out
Troubleshooting steps
Follow below troubleshooting steps to fix RPC: Port mapper failure - Timed out error.
Check NFS services on NFS server
First, check if NFS server services are running smoothly on the NFS server.
root@mynfsserver # service nfs-server status
nfs-server.service - NFS server and services
Loaded: loaded (/usr/lib/systemd/system/nfs-server.service; disabled)
Drop-In: /usr/lib/systemd/system/nfs-server.service.d
└─nfsserver.conf
/run/systemd/generator/nfs-server.service.d
└─order-with-mounts.conf
Active: active (exited) since Tue 2017-11-07 15:58:08 BRST; 6 days ago
Main PID: 1586 (code=exited, status=0/SUCCESS)
CGroup: /system.slice/nfs-server.service
The above output is from the Suse Linux server. The output may look different n different Linux distros. If it’s not running or hung, you may need to restart NFS services.
Check connectivity between NFS server and client
Make sure you are able to reach the NFS server from your client. Check using ping and telnet to NFS ports like 111 and 2049 over both protocols TCP and UDP.
root@kerneltalks # ping mynfsserver
PING lasnfsp01v.la.holcim.net (10.186.1.22) 56(84) bytes of data.
64 bytes from 10.186.1.22: icmp_seq=1 ttl=56 time=3.92 ms
64 bytes from 10.186.1.22: icmp_seq=2 ttl=56 time=3.74 ms
64 bytes from 10.186.1.22: icmp_seq=3 ttl=56 time=3.82 ms
^C
--- mynfsserver ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 3.748/3.830/3.920/0.086 ms
root@kerneltalks # telnet 10.186.1.22 2049
Trying 10.186.1.22...
Connected to 10.186.1.22.
Escape character is '^]'.
root@kerneltalks # nc -v -u mynfsserver 111
Connection to mynfsserver 111 port [udp/sunrpc] succeeded!
^C
root@kerneltalks # nc -v -u mynfsserver 2049
Connection to mynfsserver 2049 port [udp/nfs] succeeded!
^C
root@kerneltalks # nc -v mynfsserver 111
Connection to mynfsserver 111 port [tcp/sunrpc] succeeded!
^C
root@kerneltalks # nc -v mynfsserver 2049
Connection to mynfsserver 2049 port [tcp/nfs] succeeded!
^C
Check if RPC info is reachable from client
Run below command to check if you can read RPC information of the NFS server from the client machine.
If you have connectivity issue then you will see mynfsserver: RPC: Port mapper failure - Timed out error here.
Check if you can read exported share info from client
Use the below command to check if you can read exported share info from the client.
root@kerneltalks # showmount -e 10.186.1.22
Export list for 10.186.1.22:
/data *(rw,sync,no_root_squash)
Check if antivirus kernel modules are blocking the NFS
Lastly, if you have SEP 14 (Symantec Endpoint Protection) antivirus installed on your server then you need to uninstall it. For some mysterious reason, SEP 14 holds on nfsd and crashes everything to NFS. You may see below messages in dmesg of NFS server to verify if SEP kernel modules are messing up with NFS
You need a reboot after uninstalling antivirus since its kernel modules loaded in kernel won’t get freed with uninstall. For that, you need to reboot the server. You cant even remove it from the kernel as you normally remove the module from the running kernel. So reboot is a way to go after uninstalling antivirus.
root@kerneltalks # lsmod |grep sym
symev_custom_4_12_14_95_48_default_x86_64 98304 1
root@kerneltalks # modprobe -r symev_custom_4_12_14_95_48_default_x86_64
modprobe: FATAL: Module symev_custom_4_12_14_95_48_default_x86_64 is in use.
root@kerneltalks # rmmod symev_custom_4_12_14_95_48_default_x86_64
rmmod: ERROR: Module symev_custom_4_12_14_95_48_default_x86_64 is in use
root@kerneltalks # lsmod | grep sym
symev_custom_4_12_14_95_48_default_x86_64 98304 1
root@kerneltalks # modinfo symev_custom_4_12_14_95_48_default_x86_64
filename: /lib/modules/4.12.14-95.48-default/kernel/drivers/char/symev-custom-4-12-14-95-48-default-x86-64.ko
modinfo: ERROR: could not get modinfo from 'symev_custom_4_12_14_95_48_default_x86_64': No such file or directory
Once all the above commands are able to provide you expected output, you will then be ready to mount your share without any issues and the issue will be resolved.
How to resolve connectivity issue
To resolve connectivity between two servers first you need to check on network ends that two servers are able to communicate over a network. If you are running it on AWS Linux EC2 instances then you might need to check security groups to allow proper traffic.
On the OS front, you may need to check iptables settings and allow NFS ports. SELinux is also an area where you need to explore settings if you have customized SELinux running on your server. Normally by default SELinux allows NFS traffic.
Learn how to change timezone in the Linux server. Understand timezone files location, configuration files, and way to change timezone using them.
Timezone configuration
This article is a beginner’s guide to change the timezone of the Linux server. Timezone is crucial for the server since the server’s native time is displayed according to timezone.
Server’s current timezone can be checked using simple date command
root@kerneltalks # date
Tue Nov 7 17:23:54 UTC 2017
In the above output, UTC (Coordinated Universal Time) is your server’s timezone. If you want to change it to match your region or application’s user’s timezone there are three ways you can do it.
If you want to change the timezone without much hassle and without messing around system files directly jump to datetimectl command option below.
How to change timezone in Linux using /etc/localtime file
/etc/localtime is the file used by the kernel to determine the timezone. If you check your current file, its a soft link to respective timezone file in /usr/share/zoneinfo directory.
root@kerneltalks # ll /etc/localtime
lrwxrwxrwx. 1 root root 25 Jul 11 16:06 /etc/localtime -> ../usr/share/zoneinfo/UTC
root@kerneltalks # ls -lrt /usr/share/zoneinfo/
total 284
-rw-r--r--. 1 root root 17722 Dec 5 2016 zone1970.tab
-rw-r--r--. 1 root root 19153 Feb 10 2017 zone.tab
-rw-r--r--. 1 root root 4445 Feb 28 2017 iso3166.tab
-rw-r--r--. 6 root root 118 Mar 21 2017 Zulu
-rw-r--r--. 2 root root 1518 Mar 21 2017 W-SU
-rw-r--r--. 1 root root 1873 Mar 21 2017 WET
-rw-r--r--. 6 root root 118 Mar 21 2017 UTC
-rw-r--r--. 6 root root 118 Mar 21 2017 Universal
-rw-r--r--. 2 root root 118 Mar 21 2017 UCT
-rw-r--r--. 3 root root 2126 Mar 21 2017 Turkey
-rw-r--r--. 2 root root 384 Mar 21 2017 Singapore
-rw-r--r--. 2 root root 517 Mar 21 2017 ROK
-rw-r--r--. 2 root root 764 Mar 21 2017 ROC
-rw-r--r--. 1 root root 2294 Mar 21 2017 PST8PDT
-rw-r--r--. 5 root root 388 Mar 21 2017 PRC
-rw-r--r--. 3 root root 3519 Mar 21 2017 posixrules
-rw-r--r--. 2 root root 3439 Mar 21 2017 Portugal
-rw-r--r--. 2 root root 2679 Mar 21 2017 Poland
-rw-r--r--. 2 root root 2047 Mar 21 2017 NZ-CHAT
-rw-r--r--. 4 root root 2434 Mar 21 2017 NZ
-rw-r--r--. 4 root root 2427 Mar 21 2017 Navajo
-rw-r--r--. 1 root root 2294 Mar 21 2017 MST7MDT
-rw-r--r--. 1 root root 118 Mar 21 2017 MST
-rw-r--r--. 1 root root 2102 Mar 21 2017 MET
-rw-r--r--. 2 root root 641 Mar 21 2017 Libya
-rw-r--r--. 2 root root 219 Mar 21 2017 Kwajalein
-rw-r--r--. 2 root root 292 Mar 21 2017 Japan
-rw-r--r--. 2 root root 481 Mar 21 2017 Jamaica
-rw-r--r--. 3 root root 8981 Mar 21 2017 Israel
-rw-r--r--. 2 root root 1690 Mar 21 2017 Iran
-rw-r--r--. 2 root root 1174 Mar 21 2017 Iceland
-rw-r--r--. 1 root root 119 Mar 21 2017 HST
-rw-r--r--. 2 root root 1175 Mar 21 2017 Hongkong
-rw-r--r--. 10 root root 118 Mar 21 2017 Greenwich
-rw-r--r--. 10 root root 118 Mar 21 2017 GMT+0
-rw-r--r--. 10 root root 118 Mar 21 2017 GMT-0
-rw-r--r--. 10 root root 118 Mar 21 2017 GMT0
-rw-r--r--. 10 root root 118 Mar 21 2017 GMT
-rw-r--r--. 7 root root 3661 Mar 21 2017 GB-Eire
-rw-r--r--. 7 root root 3661 Mar 21 2017 GB
-rw-r--r--. 1 root root 2294 Mar 21 2017 EST5EDT
-rw-r--r--. 1 root root 118 Mar 21 2017 EST
-rw-r--r--. 2 root root 3533 Mar 21 2017 Eire
-rw-r--r--. 2 root root 1946 Mar 21 2017 Egypt
-rw-r--r--. 1 root root 1876 Mar 21 2017 EET
-rw-r--r--. 2 root root 2411 Mar 21 2017 Cuba
-rw-r--r--. 1 root root 2294 Mar 21 2017 CST6CDT
-rw-r--r--. 1 root root 2102 Mar 21 2017 CET
drwxr-xr-x. 2 root root 176 Jul 11 15:57 Indian
drwxr-xr-x. 2 root root 4096 Jul 11 15:57 Africa
drwxr-xr-x. 2 root root 53 Jul 11 15:57 Mexico
drwxr-xr-x. 2 root root 59 Jul 11 15:57 Brazil
drwxr-xr-x. 6 root root 8192 Jul 11 15:57 America
drwxr-xr-x. 2 root root 161 Jul 11 15:57 Canada
drwxr-xr-x. 2 root root 187 Jul 11 15:57 Antarctica
drwxr-xr-x. 2 root root 26 Jul 11 15:57 Arctic
drwxr-xr-x. 2 root root 4096 Jul 11 15:57 Asia
drwxr-xr-x. 2 root root 196 Jul 11 15:57 Atlantic
drwxr-xr-x. 2 root root 4096 Jul 11 15:57 Australia
drwxr-xr-x. 2 root root 45 Jul 11 15:57 Chile
drwxr-xr-x. 2 root root 4096 Jul 11 15:57 Etc
drwxr-xr-x. 2 root root 4096 Jul 11 15:57 Europe
drwxr-xr-x. 2 root root 216 Jul 11 15:57 US
drwxr-xr-x. 2 root root 4096 Jul 11 15:57 Pacific
drwxr-xr-x. 18 root root 4096 Jul 11 15:57 posix
drwxr-xr-x. 18 root root 4096 Jul 11 15:57 right
Since our test server’s timezone is UTC, you can see /etc/localtime is a soft link to /usr/share/zoneinfo/UTC. To change the timezone delete existing /etc/localtime file and create a new one with a link to the desired timezone file.
root@kerneltalks # rm /etc/localtime
rm: remove symbolic link ‘/etc/localtime’? y
root@kerneltalks # ln -s /usr/share/zoneinfo/US/Eastern /etc/localtime
root@kerneltalks # date
Tue Nov 7 12:32:19 EST 2017
You can see we have changed timezone to EST by linking new localtime file to appropriate zone file under /usr/share/zoneinfo
How to change timezone using shell variable TZ
Another way to change the timezone is to use shell variable TZ. You can do it with single line command as below :
root@kerneltalks # export TZ=Asia/Singapore
root@kerneltalks # date
Wed Nov 8 01:36:15 +08 2017
I exported the timezone variable TZ for Singapore timezone. Check the date command output. Timezone has been set to +08 which means UTC+08:00 i.e. SGT (Singapore Timezone)
But remember, this timezone setting will be available for current shell only from where you are exporting this TZ variable.
How to change timezone using /etc/timezone file
The third way to change timezone is through the use of /etc/timezone file. This is available in some distro like Ubuntu. The content of the file will be the timezone name you want to set.
root@kerneltalks # cat /etc/timezone
Etc/UTC
root@kerneltalks # date
Tue Nov 7 17:50:50 UTC 2017
You have to export the timezone variable TZ as well along with a change in /etc/timezone file. And then you can see timezone change in effect.
Change timezone using timedatectl command
You can use timedatectl command to safely change timezone when you don’t want to deal with system files and fear of messing them up.
timedatectl command used to display current timezone, list available timezones, and change timezone on the server. We have this dedicated article on timedatectl to learn this command in detail.
To change timezone of server, use timedatectl with set-timezone argument and its value.
root@kerneltalks # timedatectl set-timezone Africa/Malabo
root@kerneltalks # date
Wed Nov 15 16:59:23 WAT 2017
In the output, you can see we have changed the timezone of the server to the WAT timezone.
