Posts Tagged ‘guide’

How to yum Install Gnome GUI, Latest Guest Addition Tools, Google Chrome latest version and rdesktop / xfreerdp / remmina remote RDP VNC clients On CentOS 7 / 8

Thursday, July 29th, 2021

centos7-logo

I've just reinstalled my CentOS 7 Virtual Machine since after I tried to migrate a .vdi Virtual Box image to the new company laptop using a copy of Virtualbox VM via Microsoft OneDrive was a failure.
Thus I have rebuild all my CentOS Linux programs preinstalled on the old Virtual Machines from scratch, I use this virtual machine for a very simple tasks, so basicly most imporant tools I use is a plain SSH and VNC and Remote Desktop clients just to be able to remotely connect to remote Home based server.


1.Install GNOME Graphical Environment from command line on CentOS 7 with yum and configure it to start GUI on next OS boot


I've used a minimal CentOS installation – ISO CentOS-7-x86_64-DVD-1908.iso and this brings up the OS with a text mode only as usually CentOS is used to roll on Servers and rarely and many times admins did not want to have GUI at all, however my case is different since I do like to use Graphical Environment as I use my CentOS for all kind of testing that can be later applied to a Production machines that doesn't have a GUI, hence to install GNOME on CentOS run below cmds:
 

[root@centos ~ ]# yum group list
Loaded plugins: fastestmirror
There is no installed groups file.
Maybe run: yum groups mark convert (see man yum)
Loading mirror speeds from cached hostfile
Available Environment Groups:
 Minimal Install
 Compute Node
 Infrastructure Server
 File and Print Server
 Basic Web Server
 Virtualization Host
 Server with GUI
 GNOME Desktop
 KDE Plasma Workspaces
 Development and Creative Workstation
Available Groups:
 Compatibility Libraries
 Console Internet Tools
 Development Tools
 Graphical Administration Tools
 Legacy UNIX Compatibility
 Scientific Support
 Security Tools
 Smart Card Support
 System Administration Tools
 System Management
Done


[root@centos ~ ]# yum groupinstall "GNOME Desktop" "Graphical Administration Tools" -y


Enable GUI to be automatically start on CentOS VM boot in systemd this is configured with the "targets" instead of the well known classical runlevels (the well known /etc/inittab) is now obsolete in newer Linux distros.

[root@centos ~ ]# ln -sf /lib/systemd/system/runlevel5.target /etc/systemd/system/default.target


2. Install Guest Additions Tools on CentOS


The most basic thing to do once I've had the CentOS Linux release 7.7.1908 (Core) rolled out on the VirtualBox is of course to enable Guest Additions Tools

First I had to install of course Guest Additions Tools to allow myself to have a copy paste in clip board via the Host Machine (Windows 10) and the Guest Machine.
To do I had to:

[root@centos ~ ]# yum install kernel-headers.x86_64 -y

[root@centos ~ ]# rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

[root@centos ~ ]#  yum install perl gcc dkms kernel-devel kernel-headers make bzip2

To check the required VBoxLinuxAdditions.run script kernel headers are at place:

[root@centos ~ ]# ls -l /usr/src/kernels/$(uname -r)

…
You should get a list of kernel header files

Then once I've done the Insert Guest Additions CD Image from the VirtualBox VM upper menu. I've had to mount and load the guest additions via the script:
 

[root@centos ~ ]# mkdir /mnt/cdrom
[root@centos ~ ]# mount /dev/cdrom /mnt/cdrom
[root@centos ~ ]# sh VBoxLinuxAdditions.run

After rebooting the Virtual Machine, I've used the full screen functionality to test and configured immediately Shared Clipboard and Drag and Drop to be both set to (Bidirectional) as well as configured a Shared folder to provide my Windows Desktop under /mnt/shared_folder (as read write) as I usually do to be able to easily copy files from the VM and to the Windows.

3. Install Google Chrome on the CentOS Virtual Machine with yum
 

Next I've installed the chrome browser that was pretty trivial it is up to fetching the required 32 or 64 bit latest chrome binary this is usually on URL:

[root@centos ~ ]# wget https://dl.google.com/linux/direct/google-chrome-stable_current_x86_64.rpm

and installing Google Chrome with superuser with command:

[root@centos ~ ]# yum install ./google-chrome-stable_current_*.rpm -y

 

Loaded plugins: fastestmirror, langpacks
Examining ./google-chrome-stable_current_x86_64.rpm: google-chrome-stable-92.0.4515.107-1.x86_64
Marking ./google-chrome-stable_current_x86_64.rpm to be installed
Resolving Dependencies
–> Running transaction check
—> Package google-chrome-stable.x86_64 0:92.0.4515.107-1 will be installed
–> Processing Dependency: liberation-fonts for package: google-chrome-stable-92.0.4515.107-1.x86_64
Loading mirror speeds from cached hostfile
 * base: mirror.digitalnova.at
 * epel: fedora.ipacct.com
 * extras: mirror.digitalnova.at
 * updates: mirror.digitalnova.at
–> Processing Dependency: libvulkan.so.1()(64bit) for package: google-chrome-stable-92.0.4515.107-1.x86_64
–> Running transaction check
—> Package liberation-fonts.noarch 1:1.07.2-16.el7 will be installed
–> Processing Dependency: liberation-narrow-fonts = 1:1.07.2-16.el7 for package: 1:liberation-fonts-1.07.2-16.el7.noarch
—> Package vulkan.x86_64 0:1.1.97.0-1.el7 will be installed
–> Processing Dependency: vulkan-filesystem = 1.1.97.0-1.el7 for package: vulkan-1.1.97.0-1.el7.x86_64
–> Running transaction check
—> Package liberation-narrow-fonts.noarch 1:1.07.2-16.el7 will be installed
—> Package vulkan-filesystem.noarch 0:1.1.97.0-1.el7 will be installed
–> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package                 Arch   Version         Repository                 Size
================================================================================
Installing:
 google-chrome-stable    x86_64 92.0.4515.107-1 /google-chrome-stable_current_x86_64
                                                                          259 M
Installing for dependencies:
 liberation-fonts        noarch 1:1.07.2-16.el7 base                       13 k
 liberation-narrow-fonts noarch 1:1.07.2-16.el7 base                      202 k
 vulkan                  x86_64 1.1.97.0-1.el7  base                      3.6 M
 vulkan-filesystem       noarch 1.1.97.0-1.el7  base                      6.3 k

Transaction Summary
================================================================================
Install  1 Package (+4 Dependent packages)

Total size: 263 M
Total download size: 3.8 M
Installed size: 281 M
Is this ok [y/d/N]: y
Downloading packages:
(1/4): liberation-fonts-1.07.2-16.el7.noarch.rpm           |  13 kB   00:00     
(2/4): liberation-narrow-fonts-1.07.2-16.el7.noarch.rpm    | 202 kB   00:00     
(3/4): vulkan-filesystem-1.1.97.0-1.el7.noarch.rpm         | 6.3 kB   00:00     
(4/4): vulkan-1.1.97.0-1.el7.x86_64.rpm                    | 3.6 MB   00:00     
——————————————————————————–
Total                                              3.0 MB/s | 3.8 MB  00:01     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : vulkan-filesystem-1.1.97.0-1.el7.noarch                      1/5 
  Installing : vulkan-1.1.97.0-1.el7.x86_64                                 2/5 
  Installing : 1:liberation-narrow-fonts-1.07.2-16.el7.noarch               3/5 
  Installing : 1:liberation-fonts-1.07.2-16.el7.noarch                      4/5 
  Installing : google-chrome-stable-92.0.4515.107-1.x86_64                  5/5 
  Verifying  : vulkan-1.1.97.0-1.el7.x86_64                                 1/5 
  Verifying  : 1:liberation-narrow-fonts-1.07.2-16.el7.noarch               2/5 
  Verifying  : 1:liberation-fonts-1.07.2-16.el7.noarch                      3/5 
  Verifying  : google-chrome-stable-92.0.4515.107-1.x86_64                  4/5 
  Verifying  : vulkan-filesystem-1.1.97.0-1.el7.noarch                      5/5 

Installed:
  google-chrome-stable.x86_64 0:92.0.4515.107-1                                 

Dependency Installed:
  liberation-fonts.noarch 1:1.07.2-16.el7                                       
  liberation-narrow-fonts.noarch 1:1.07.2-16.el7                                
  vulkan.x86_64 0:1.1.97.0-1.el7                                                
  vulkan-filesystem.noarch 0:1.1.97.0-1.el7             
…


4. Install usable Windows VNC and remote desktop (RDP Client) for CentOS Linux


There is a plenty of clients to choice from if you need to have an RDP client for Linux, but perhaps the most useful ones I usually use are remmina / rdesktop and freerdp. Usually I use remmina on Debian Linux, but under the VM somehow I was not able to make remmina work in Full Screen mode while connected to remote Windows 7 VPS server, thus I've first tried xfreerdp (that comes from default CentOS repositories) and is open source alternative to rdesktop (which is non free distributed binary).
 

[root@centos ~ ]$ sudo yum -y install freerdp


The basic use is:

[hipo@centos ~ ]$ xfreerdp –toggle-fullscreen <remote-server-address>


Unfortunately I did not succeeded to make xfreerdp be able to show me remote desktop in FullScreen mode so had to use additional repository package called nux-dextop to have rdesktop at my disposal.

To install it had to run:

[root@centos ~ ]# rpm –import http://li.nux.ro/download/nux/RPM-GPG-KEY-nux.ro 
[root@centos ~ ]# rpm -Uvh http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-1.el7.nux.noarch.rpm    
[root@centos ~ ]# yum install rdesktop

To connect to the remote RDP host in Fullscreen with rdesktop :
 

rdesktop -f <remote-server-address>

windows-7-remote-desktop-screenshot-connected-with-rdesktop

As telnet is not installed by default and it is so useful to check ports

5. Install GNU Image Manipulation Program for better screnshotting and Graphic edits


I usually do install GIMP (GNU Image Manipulation Program) since this is my favourite tool to make screenshot on Linux as well as do some minor graphic edits whenever necessery. I warmly recommend gimp to anyone. If you don't have basic GIMP tool and you plan to be daily working a lot with Linux sooner or later some skills with the program will be of a major use even for the most advanced sysadmin :)_

root@centos ~ ]# yum install -y gimp

 

6. Install useful administration tools for daily sysadmin work – telnet, nmap, iftop, htop, iotop, iptraf-ng, tcpdump

 

Having basic analys tools and remote communication port testing, DNS, resolving and connection, cpu, mem statistics I find mostly useful. 

[root@centos .ssh]# yum install telnet nmap iftop htop vnstat sysstat iptraf-ng bind-utils -y
…

 

 

7. Set Open Explorer and SHOW Desktop key binding shortcuts for GNOME (to make daily work easier)

 


Another useful I do use in my newly installed Virtual Machines is the key combination of Windows (button key) + E – to easily open the GNOME equivalent of Windows Explorer (Nautilus) and Windows (key) + D to hide the active selected Window and Show Desktop. This is configured pretty easy in GNOME through:
 

$ gnome-control-center

Keyboard (Section)

Perhaps there is other stuff I need to add on the freshly installed Operating System if I remember something else interesting

configure-home-folder-and-hide-all-normal-windows-gnome-key-binding-howto-screenshot

 

8. Install gnome-tweaks to tweak a bit the desktop icon positionsing and additional gnome-shell extras

[root@centos hipo]# yum install -y gnome-shell-extension-workspace-indicator.noarch gnome-shell-extension-workspace-indicator.noarch gnome-shell-extension-suspend-button.noarch gnome-shell-extension-refresh-wifi.noarch gnome-shell-extension-updates-dialog.noarch gnome-shell-extension-windowoverlay-icons.noarch gnome-shell-extension-places-menu.noarch gnome-shell-extension-drive-menu.noarch gnome-shell-extension-apps-menu.noarch gnome-shell-extension-auto-move-windows.noarch gnome-tweaks gnome-shell-extension-systemMonitor.noarch gnome-shell-extension-openweather.noarch gnome-shell-extension-user-theme.noarch gnome-shell-extension-topicons-plus.noarch


Next step is to use gnome-tweaks to set multiple custom preference stuff you like on the gnome 3.28 GUI 

 

gnome-tweak-tool1

gnome-tweak-tool2

gnome-tweak-tool3

9. Change ( Fix) timezone to correct time on the Virtual Machine

[root@localhost ~]# timedatectl 
      Local time: Fri 2021-07-30 12:20:51 CEST
  Universal time: Fri 2021-07-30 10:20:51 UTC
        RTC time: Fri 2021-07-30 10:20:48
       Time zone: Europe/Berlin (CEST, +0200)
     NTP enabled: yes
NTP synchronized: yes
 RTC in local TZ: no
      DST active: yes
 Last DST change: DST began at
                  Sun 2021-03-28 01:59:59 CET
                  Sun 2021-03-28 03:00:00 CEST
 Next DST change: DST ends (the clock jumps one hour backwards) at
                  Sun 2021-10-31 02:59:59 CEST
                  Sun 2021-10-31 02:00:00 CET

[root@localhost ~]# ls -l /etc/localtime
lrwxrwxrwx. 1 root root 35 Jul 29 14:03 /etc/localtime -> ../usr/share/zoneinfo/Europe/Berlin


To change to correct timezone, you need to find out the long name for the timezone you want to use. The timezone naming convention usually uses “Region/City” format.

To list all available time zones, you can either list the files in the /usr/share/zoneinfo directory or use the timedatectl command.

[root@centos ~]# timedatectl list-timezones|tail -n 10
Pacific/Pohnpei
Pacific/Port_Moresby
Pacific/Rarotonga
Pacific/Saipan
Pacific/Tahiti
Pacific/Tarawa
Pacific/Tongatapu
Pacific/Wake
Pacific/Wallis
UTC


As I'm situated in Sofia Bulgaria to set the correct timezone to UTC (Universal Time Clock)  + 2 Hrs, i've checked the correct Continent/Country like so:

[root@centos ~]# timedatectl list-timezones|grep -i Sofia
Europe/Sofia

Once I've my Capital / Country time location  identified to set to it:

[root@centos ~]# timedatectl set-timezone your_time_zone

 

10. Configure remote connection hostname SSH aliases via ssh config ( ~/.ssh/config)

 


I'm having separate Virtual Machines running on my OpenXen virtualization Hypervisor server at different ports which I remember by heart under different hostnames, this saves me time to always type on command line long commands such as:
 

 

 

#  ssh long-hostname -p Port_number

 to make accessibility to remote machines via a simple Hostname Aliases, that forwards to remote port (that gets forwarded via a Local Network configure Netwrork Address Translation), I use the .ssh/config nice Host / Hostname / User / Port directives like below samples:

[hipo@centos .ssh]$ cat config 
Host pcfreak
User root
Port 2248
HostName 83.228.93.76

Host freak
User root
Port 2249
HostName 213.91.190.233


Host pcfrxenweb
User root
Port 2251
Hostname 83.228.93.76

Host pcfrxen
User root
Port 2250
Hostname 213.91.190.233
…

Now to connect to pcfrxen for example I simply type:

ssh pcfrxen

type in the password to remote VM and I'm in 🙂

The same could be achieved also with Adding Custom Hostname IP Aliases via ~/.bashrc or iteration script as I've explained earlier that fakes like custom /etc/hosts, but I usuaully prefer to use .ssh/config instead like explained above.

Note that above steps should work also on RHEL / Fedora Linux with a minor modifications, as usually this two distros share the RPM package manager. If someone tries to follow the guide and have success on any of this distros please drop a comment with feedback.

Tags: , , , , , , , , , ,
Posted in Linux, System Administration, Virtual Machines | No Comments »

How to fix “sslserver: fatal: unable to load certificate” Qmail error on GNU / Linux

Friday, October 14th, 2011

After setupping a brand new Qmail installation following the QmailRocks Thibs Qmail Debian install guide , I’ve come across unexpected re-occuring error message in /var/log/qmail/qmail-smtpdssl/ , here is the message:

@400000004e9807b10d8bdb7c command-line: exec sslserver -e -vR -l my-mailserver-domain.com -c 30 -u 89 -g 89
-x /etc/tcp.smtp.cdb 0 465 rblsmtpd -r zen.spamhaus.org -r dnsbl.njabl.org -r dnsbl.sorbs.net -r bl.spamcop.net qmail-smtpd
my-mailserver-domain.com /home/vpopmail/bin/vchkpw /bin/true 2>&1
@400000004e9807b10dae2ca4 sslserver: fatal: unable to load certificate

I was completely puzzled initially by the error as the sertificate file /var/qmail/control/servercert.pem was an existing and properly self generated one. Besides that qmail daemontools init script /service/qmail-smtpd/run was loading the file just fine, where the same file failed to get loaded when sslserver command with the cert argument was invoked via /service/qmail-smtpdssl/run

It took me quite a while to thoroughfully investigate on what’s wrong with the new qmail install. Thanksfully after almost an hour of puzzling I found it out and I was feeling as a complete moron to find that the all issues was caused by incorrect permissions of the /var/qmail/control/servercert.pem file.
Here are the incorrect permissions the file possessed:

linux:~# ls -al /var/qmail/control/servercert.pem
-rw------- 1 qmaild qmail 2311 2011-10-12 13:21 /var/qmail/control/servercert.pem

To fix up the error I had to allow all users to have reading permissions over servercert.pem , e.g.:

linux:~# chmod a+r /var/qmail/control/servercert.pem

After adding all users readable bit on servercert.pem the file permissions are like so:

linux:~# ls -al /var/qmail/control/servercert.pem
-rw-r--r-- 1 qmaild qmail 2311 2011-10-12 13:21 /var/qmail/control/servercert.pem

Consequently I did a qmail restart to make sure the new readable servercert.pem will get loaded from the respective init script:

linux:~# qmailctl restart
* Stopping qmail-smtpdssl.
* Stopping qmail-smtpd.
* Sending qmail-send SIGTERM and restarting.
* Restarting qmail-smtpd.
* Restarting qmail-smtpdssl.

Now the annoying sslserver: fatal: unable to load certificate message is no more and all works fine, Hooray! 😉

Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
Posted in Linux, Qmail, System Administration | 3 Comments »

How to add Apache 301 redirect to VirtualHost in Apache

Sunday, September 25th, 2011

I’ve had two domain names which were pointing to the same website content.
As one can read in any SEO guide around this is a really bad practice as search engines things automatically there is a duplicate site content and this has automatically a negative effect on the site pagerank.
To deal with situation where multiple domains are pointing to the same websites its suggested by many SEO specialists that a 301 redirect is created from all the domain websites to a single website domain which will open the actual website.

Making the 301 direct domain from the sample domain my-redirect-domain.com to www.mydomain.com can be done with a virtualhost dfefinition in either httpd.conf or with the respective file containing the domain virtualhost definitions:
Here is the exact VirtualHost code I use to make a 301 redirect.

<VirtualHost *>  ServerAdmin support@mydomain.com  ServerName my-redirected-domain.com
ServerAlias my-redirected-domain.com www.my-redirected-domain.com
RewriteEngine on RewriteRule ^/(.*) http://www.mydomain.com/$1 [L,R=301]
</VirtualHost>

After placing the VirtualHost redirect, an apache redirect is required.
Further on when a Gooogle or Yahoo Bot visits the website and does any request to my-redirect-domain.com or www.my-redirect-domain.com , they will be redirected with a 301 reuturned code to www.mydomain.com

This kind of redirect however can have a negative impact on the Apache CPU use (performance), especially if the my-redirect-domain.com is high traffic domain. This is because the redirect is done with mod_rewrite.

Therefore it might be better on high traffic domains to create the mod_rewrite redirect by using a vhost like:

<VirtualHost *>
ServerAdmin support@mydomain.com
ServerName my-redirected-domain.com
Redirect 301 / http://www.mydomain.com/
</VirtualHost>

The downside of using the Apache 301 redirect capabilities like in the above example is that any passed domain urls like let’s say http://www.my-redirected-domain.com/support/ would not be 301 redirected to http://www.mydomain.com/support/ but instead the redirect will be done straight to http://www.mydomain.com/

Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
Posted in SEO, System Administration, Various, Web and CMS | 2 Comments »

Complete guide to fix PulseAudio and video/audio VLC Media Player issues (F11_VLC_and_PulseAudio_Guide.pdf)

Tuesday, February 9th, 2010

I’ve found a nice guide discussing some major common problem with pulseaudio and VLC,
sound and video streaming annoyances.
The guide was available only through fedoraforum.org
and in order to fetch it the user needs account in fedoraforum, that is incredibly annoying.
Originally the guide targetted Fedora and other RedHat based distributions, however most
of the information in the tutorial is pretty accurate on other distributions as well.
For instance I use Debian and almost everything described in the tutor is equivalent;
So, Here is download link to the F11_VLC_and_PulseAudio_Guide.pdf
I hope this mirror of F11_VLC_and_PulseAudio_Guide.pdf
would save some time and nerves needed for registration in fedoraforum.org in order to download the file

Tags: , , , , ,
Posted in Linux Audio & Video | 1 Comment »

Download scanned electronic version of The way of the Rat: A Survival Guide to Office Politics by Joep P. M. Schrijvers

Monday, February 8th, 2010

The way of the rat cover

We were obliged in Arnhem Business School to read the book, The way of the rat: A Survival Guide to Office Politics
I looked for the book everywhere online in Torrents, all kind of download areas etc. and I couldn’t find the book
anywhere. I finally surrendered and decided to purchase the book via ebay
It took it a month or so to come to my address, anyways in the meantime I met a friend, who borrowed the book
from a friend and scanned the entire book.
I asked if I can own the copy so he was generous and shared it, so I thought many other students like me
would be looking for the book in a desperate attempt to save some approximately $10 EUR (that’s the book costs).

That is why I copied the scanned version of the Way of the Rat to my personal apache web server and decided to
share it here.

Follow the link below to download:
Download here The way of the Rat: A Survival Guide to OfficePolitics
I have to warn you the scanning quality is terrible, though the text is readable.
Hope the book would be of use to some students out there who are studying business management.

Tags: , , , , ,
Posted in Business Management | 14 Comments »