Category: CentOS

Install CentOS 8 from Net boot ISO
CentOS 8 provide 2 type of ISO. One that ends with boot.iso, this is 534 MB. This only include essential files to get you started with installation. This installation method require internet connection as files needed to be downloaded from internet. Other ISO file is full install media, that is 6.6 GB in size. To install from boot.iso, download it from

http://isoredirect.centos.org/centos/8/isos/x86_64/

This page will list morrors near to you.

Click on any of the morror from link, on next page, you will see ISO files. Download CentOS-8-x86_64-xxxx-boot.iso

Write this ISO file into a USB drive or DVD, then boot your computer with it. You will see following screen.

Select first or second option. 2nd option test install media for any errors. If you use USB drive, you can just select option 1 as there is less chance of media corruption compared to DVD drives.

Select language, click continue.

On this screen, you need to make several choices.

Installation Destination

Select the hard disk where you need CentOS 8 installed.

If you have an empty disk, all you need to do is click “Done”.

If your disk have existing partitions, you may need to delete it before insalling CentOS 8. If you have any data on this hard disk, always take a backup before you installing new OS.

Network & Host Name

You need to configure your network. Most of the time all you need to do is click on ON/OFF toggle on right side of the network interface.

If you have DHCP on your network, you will see IP address assigned to your computer. If not, you need to manually configure networking. It is important as you will need internet to do CentOS 8 install using boot ISO file. Click Done to go back to previous screen.

Installation Source

On this page, you need to enter a CentOS mirror. You can use following URL
```
http://mirror.centos.org/centos/8/BaseOS/x86_64/os/
```
It is better to use a CentOS mirror near to you. This will make file downloads faster. In my case, i used
```
http://centos.mirrors.estointernet.in/8.0.1905/BaseOS/x86_64/os/
```
There is option to select mirror near you on this screen. But for some reason, this option did not work for me.

Software Slection

On this screen, you need to select software to install.

You can select if you need to install GUI or just minimal CentOS install. I selected minimal install as everything else can be installed later as needed.

Click “Done”, will take you to previous screen. Now you will see “Begin Installation” button enabled. Click on it to continue installation.

On next screen, you get option to set password. Set password for user root. You can also create a new user if required.

Installation take 15 to 30 minutes depending on your download speed. Once installation completed, you will be asked to reboot.

CentOS 8 use Kernel 4.18
```
[root@192 ~]# hostnamectl 
   Static hostname: localhost.localdomain
Transient hostname: 192.168.1.5
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 7ad955dffb89464a96918974be28795b
           Boot ID: 77cd4c012cbe4b6f9c33ab7dae5ecc33
    Virtualization: oracle
  Operating System: CentOS Linux 8 (Core)
       CPE OS Name: cpe:/o:centos:centos:8
            Kernel: Linux 4.18.0-80.7.1.el8_0.x86_64
      Architecture: x86-64
[root@192 ~]# 
```
You can use both yum and dnf for installing software.
September 27, 2019
CentOS 8
CentOS 8 is a short-lived Linux distribution based on Red Hat Enterprise Linux (RHEL). Due to a change in policy, CentOS 8 had an early end of life on December 31, 2021.

If you are using CentOS 8, you can easily migrate to other RHEL based distributions like Alma Linux, RockyLinux or Oracle Linux.

CentOS will now provide CentOS 8 Stream, which is a rolling release Linux distribution. CentOS 8 Stream will position itself in the middle of Fedora and RHEL. It won’t be a copy of RHEL, instead, it will be used as a testing ground for RHEL. Newer versions of the software get released on CentOS 8 Stream, once it becomes stable, it will be included in RHEL.
September 26, 2019
Run Apache from command line
To start Apache from command line with out using a systemd service file or init script, run
```
/usr/sbin/httpd -DFOREGROUND
```
To stop Apache, press CTRL+C.

You can keep it running by running it inside screen or tmux.

See Apache
September 25, 2019
Download RPM package from yum repository
To download RPM file from yum repo, you need to install yum-utils package.
```
yum install -y yum-utils
```
Now you can use command
```
yumdownloader --resolve --destdir=/path/ PACKAGE_NAME
```
Example
```
yumdownloader --resolve --destdir=/root/yum/ nginx
```
This will download and store all rpm files in /var/yum folder. –resolve will resolve dependency and download them. This will be helpful if you need to install a package on a system with no direct internet connection.

See yum
September 15, 2019
Setup Tor Hidden Service on CentOS 7
Tor is provided by EPEL repository on CentOS 7. Install EPEL repo with command
```
yum install epel-release
```
Install tor
```
yum install tor
```
Edit tor config file
```
vi /etc/tor/torrc
```
Uncomment or add following lines
```
HiddenServiceDir /var/lib/tor/hidden_service/
HiddenServicePort 80 127.0.0.1:80
```
Restart tor with command
```
systemctl restart tor
```
Now your tor hidden service is ready to use. You need to run your web application on 127.0.0.1:80

To see URL of your tor hidden service, run
```
cat /var/lib/tor/hidden_service/hostname
```
Make sure to make a backup of folder “/var/lib/tor/hidden_service/” as it comtains keys for this .onion domain. If you lost it, you will lose your domain name. So it is very important you keep the files safe.

To stop/start tor, run
```
systemctl stop tor
systemctl start tor
```
See tor
September 11, 2019

yum-config-manager

yum-config-manager allows you to manage yum repositories.

To add a repo, run

yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

Disable a repository

yum-config-manager --disable rpmfusion-free-updates

See yum

August 9, 2019

CentOS add IP Address
To add IP address on a Linux server, first find name of your network interface. This can be done with command
```
ip link
```
In most case, it can be enp3s0 or eth0, if you have more than one network card, this may be differnt, in such case, you need to identify which network interface you need to configure the the IP address .

Now create file
```
vi /etc/sysconfig/network-scripts/ifcfg-enp3s0:1
```
Here i used enp3s0 as network inferface name, replace it with whatever network interface name you use.

Add following content
```
DEVICE="enp3s0:1"
IPADDR=IP_ADDR_HERE
NETMASK=255.255.255.255
```
IP_ADDR_HERE = replace with the IP address you need to add.

enp3s0 = replace with actual network interface name.

Restart network service with command
```
systemctl restart network
```
If you need to add another IP, create file with name
```
INTERFACE_NAME:2
```
for example “enp3s0:2”, you need to use same alias name in DEVICE entry (first line) in the file.

Adding IP Range in CentOS 6
August 5, 2019
Install vnstat on CentOS 7
To install vnstat on CentOS 7, run
```
yum install vnstat -y
```
Now create database for your network interface card
```
vnstat --create -i NETWORK_INTERFACE_NAME
```
Restart vnstat deamon
```
systemctl restart vnstat
```
See vnstat
July 15, 2019
Install Transmission on CentOS
transmission is a torrent client. This come with a web GUI, that make it easy to installed on a remote server with no X-Windows. To install transmission on CentOS server, run
```
yum install -y transmission-daemon transmission-cli
```
Allow Web Access

To access transmission web GUI, you need to white list your IP address. To do this, first stop tranmission
```
service transmission-daemon stop
```
Edit file
```
vi /var/lib/transmission/.config/transmission/settings.json
```
Find
```
    "rpc-whitelist": "127.0.0.1",
```
Replace with
```
    "rpc-whitelist": "127.0.0.1,YOUR_IP_ADDR_HERE",
```
YOUR_IP_ADDR_HERE – replace with your actual IP address.

Start transmission
```
service transmission-daemon start
```
You will be able to access web GUI at
```
http://YOUR_SERVER_IP:9091
```
Downloaded files are stored in folder
```
/var/lib/transmission/Downloads
```
July 5, 2019

Install MongoDB 4.0 on CentOS 7

To install MongoDB 4.0 (for other versions, see release note) on CentOS 7, create file

vi /etc/yum.repos.d/mongodb-org-4.0.repo

Add content

[mongodb-org-4.0]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.0/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-4.0.asc

Install MongoDB with

yum install -y mongodb-org

Enable MongoDB start on boot

systemctl enable mongod

Start Mongo DB with

systemctl start mongod

To see mongoDB version, run

[root@ns3084948 ~]# mongo --version
MongoDB shell version v4.0.10
git version: c389e7f69f637f7a1ac3cc9fae843b635f20b766
OpenSSL version: OpenSSL 1.0.1e-fips 11 Feb 2013
allocator: tcmalloc
modules: none
build environment:
    distmod: rhel70
    distarch: x86_64
    target_arch: x86_64
[root@ns3084948 ~]#

To see if mongoDB running

[root@ns3084948 ~]# netstat -lntp | grep mongo
tcp        0      0 127.0.0.1:27017         0.0.0.0:*               LISTEN      10349/mongod        
[root@ns3084948 ~]#

Or use

[root@ns3084948 ~]# systemctl status mongod
● mongod.service - MongoDB Database Server
   Loaded: loaded (/usr/lib/systemd/system/mongod.service; enabled; vendor preset: disabled)
   Active: active (running) since Tue 2019-06-04 06:08:01 BST; 18min ago
     Docs: https://docs.mongodb.org/manual
  Process: 10347 ExecStart=/usr/bin/mongod $OPTIONS (code=exited, status=0/SUCCESS)
  Process: 10344 ExecStartPre=/usr/bin/chmod 0755 /var/run/mongodb (code=exited, status=0/SUCCESS)
  Process: 10341 ExecStartPre=/usr/bin/chown mongod:mongod /var/run/mongodb (code=exited, status=0/SUCCESS)
  Process: 10338 ExecStartPre=/usr/bin/mkdir -p /var/run/mongodb (code=exited, status=0/SUCCESS)
 Main PID: 10349 (mongod)
   Memory: 46.7M
   CGroup: /system.slice/mongod.service
           └─10349 /usr/bin/mongod -f /etc/mongod.conf

Jun 04 06:07:57 ns3084948.ip-145-239-4.eu systemd[1]: Starting MongoDB Database Server...
Jun 04 06:07:58 ns3084948.ip-145-239-4.eu mongod[10347]: 2019-06-04T06:07:58.013+0100 I CONTROL  [main] WARNING: Cannot detect if NUMA interleaving is enabled. Failed to probe "/sys/devices...ssion denied
Jun 04 06:07:58 ns3084948.ip-145-239-4.eu mongod[10347]: about to fork child process, waiting until server is ready for connections.
Jun 04 06:07:58 ns3084948.ip-145-239-4.eu mongod[10347]: forked process: 10349
Jun 04 06:08:01 ns3084948.ip-145-239-4.eu mongod[10347]: child process started successfully, parent exiting
Jun 04 06:08:01 ns3084948.ip-145-239-4.eu systemd[1]: Started MongoDB Database Server.
Hint: Some lines were ellipsized, use -l to show in full.
[root@ns3084948 ~]#

June 4, 2019

List all files in an rpm package
To list all files in an rpm package run
```
rpm -ql PACKAGE_NAME
```
May 28, 2019

Install vsftpd on CentOS

To install vsftpd FTP server in CentOS, run

yum install -y vsftpd

Enable vsftpd to start on boot

systemctl enable vsftpd

Edit configuration file

vi /etc/vsftpd/vsftpd.conf

You need to update/add following configuration options

chroot_local_user=YES
allow_writeable_chroot=YES
local_umask=002
file_open_mode=0755
force_dot_files=YES

Restart vsftpd

systemctl restart vsftpd

Allow System Accounts to login

local_enable=YES
write_enable=YES

Find

anonymous_enable=YES

Replace With

anonymous_enable=NO

Find

#chroot_local_user=YES

Replace with

chroot_local_user=YES

Add

allow_writeable_chroot=YES
local_umask=002
file_open_mode=0755

See vsftpd

March 28, 2019

Category: CentOS

Allow Web Access

Allow System Accounts to login