Category: CentOS

Install elasticsearch on CentOS 7

To install elasticsearch, first install java

yum -y install java-1.8.0-openjdk

Import key

rpm --import https://artifacts.elastic.co/GPG-KEY-elasticsearch

Create file

vi /etc/yum.repos.d/elasticsearch.repo

Paste following

[elasticsearch]
name=Elasticsearch repository for 7.x packages
baseurl=https://artifacts.elastic.co/packages/7.x/yum
gpgcheck=1
gpgkey=https://artifacts.elastic.co/GPG-KEY-elasticsearch
enabled=0
autorefresh=1
type=rpm-md

Install elasticsearch

yum install --enablerepo=elasticsearch elasticsearch

Set elastic search to start on boot

systemctl enable elasticsearch

To start/stop/status

systemctl stop elasticsearch.service
systemctl start elasticsearch.service
systemctl status elasticsearch.service

To see logs

tail -f /var/log/elasticsearch/elasticsearch.log

ElasticSearch runs on port 9200

[root@server ~]# netstat -lntp | grep java
tcp6       0      0 127.0.0.1:9200          :::*                    LISTEN      1289/java           
tcp6       0      0 ::1:9200                :::*                    LISTEN      1289/java           
tcp6       0      0 127.0.0.1:9300          :::*                    LISTEN      1289/java           
tcp6       0      0 ::1:9300                :::*                    LISTEN      1289/java           
[root@server ~]#

If you get error starting elasticsearch, check Elasticsearch failed to start on CentOS 7

If you have a previous installation, make sure you delete left over files before you install differnt version of elasticsearch. I removed following files/folders when i had to downgrade elasticsearch.

/etc/sysconfig/elasticsearch.rpmsave
/var/lib/elasticsearch
/var/log/elasticsearch

See elasticsearch

August 15, 2020

yum [Errno 5] [Errno 2] No such file or directory

When running yum update on CentOS 7 server, i get following error

[root@server2 yum.repos.d]# yum update curl
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Resolving Dependencies
--> Running transaction check
---> Package curl.x86_64 0:7.29.0-54.el7 will be updated
---> Package curl.x86_64 0:7.29.0-57.el7_8.1 will be an update
--> Processing Dependency: libcurl = 7.29.0-57.el7_8.1 for package: curl-7.29.0-57.el7_8.1.x86_64
--> Running transaction check
---> Package libcurl.x86_64 0:7.29.0-54.el7 will be updated
--> Processing Dependency: libcurl = 7.29.0-54.el7 for package: libcurl-devel-7.29.0-54.el7.x86_64
---> Package libcurl.x86_64 0:7.29.0-57.el7_8.1 will be an update
--> Running transaction check
---> Package libcurl-devel.x86_64 0:7.29.0-54.el7 will be updated
---> Package libcurl-devel.x86_64 0:7.29.0-57.el7_8.1 will be an update
--> Finished Dependency Resolution

Dependencies Resolved

============================================================================================================================================================================================================
 Package                                            Arch                                        Version                                                  Repository                                    Size
============================================================================================================================================================================================================
Updating:
 curl                                               x86_64                                      7.29.0-57.el7_8.1                                        updates                                      271 k
Updating for dependencies:
 libcurl                                            x86_64                                      7.29.0-57.el7_8.1                                        updates                                      223 k
 libcurl-devel                                      x86_64                                      7.29.0-57.el7_8.1                                        updates                                      303 k

Transaction Summary
============================================================================================================================================================================================================
Upgrade  1 Package (+2 Dependent packages)

Total download size: 796 k
Is this ok [y/d/N]: y
Downloading packages:
No Presto metadata available for updates


Error downloading packages:
  libcurl-7.29.0-57.el7_8.1.x86_64: [Errno 5] [Errno 2] No such file or directory
  libcurl-devel-7.29.0-57.el7_8.1.x86_64: [Errno 5] [Errno 2] No such file or directory
  curl-7.29.0-57.el7_8.1.x86_64: [Errno 5] [Errno 2] No such file or directory

[root@server2 yum.repos.d]#

Someone had tried to install differnt version of python on this server. That caused this problem.

When i run urlgrabber-ext-down, i get error saying python missing.

[root@server2 ~]# /usr/libexec/urlgrabber-ext-down
-bash: /usr/libexec/urlgrabber-ext-down: /usr/bin/python: bad interpreter: No such file or directory
[root@server2 ~]#

Problem fixed by creating symlink

ln -s /usr/bin/python2.7 /usr/bin/python

See yum

August 8, 2020

Install bind in CentOS 7

bind is a DNS server. To install bind on CentOS 7, run

yum install bind bind-utils -y

Enable bind to start on boot

systemctl enable named

Start bind

systemctl start named

You can see status with

systemctl status named

Setup firewall

You need to allow DNS ports UDP/TCP 53 in firewall. On CentOS 7, you can run

firewall-cmd --zone=public --permanent --add-service=dns
firewall-cmd --reload

Configure bind

By default bind only listens to local IP, to make it accessable from outside, you need to edit named.conf

vi /etc/named.conf

Find

        listen-on port 53 { 127.0.0.1; };
        listen-on-v6 port 53 { ::1; };

Comment out those two lines by adding # at start of the lines.

        #listen-on port 53 { 127.0.0.1; };
        #listen-on-v6 port 53 { ::1; };

We need our DNS server access query from anyone on internet. For this, find

        allow-query     { localhost; };

Replace with

        allow-query     { any; };

Since we only want our DNS server resolve domains hosted on our server, disable recursion.

Find

        recursion yes;

Replace with

        recursion no;

Now restart bind with

systemctl restart bind

Adding Domain to bind

To server a domain, you need to add the domain to bind. For this edit file

vi /etc/named.conf

at end of the file, add

zone "DOMAIN.EXTN" IN {
   type master;
   file "/var/named/DOMAIN.EXTN.zone";
   allow-update { none; };
};

Now create zone file

vi /var/named/DOMAIN.EXTN.zone

Add following

$TTL            86400
@                 IN SOA            DOMAIN.EXT.  admin.DOMAIN.EXT. (
100     ; serial
1H      ; refresh
1M      ; retry
1W      ; expiry
1D )    ; minimum
@                   IN NS             ns1.DOMAIN.EXT.
@                   IN A                 YOUR_IP_ADDR_HERE
ns1                 IN A                 YOUR_IP_ADDR_HERE
@                   IN MX   10      mail.DOMAIN.EXT.
mail                IN A                 YOUR_IP_ADDR_HERE
www                 IN A                 YOUR_IP_ADDR_HERE

Restart bind

vi /var/named/DOMAIN.EXTN.zone

You can verify domain is resolving with command

nslookup DOMAIN.EXT SERVER_IP_HERE

See bind

July 24, 2020

Install Python 3.8 on CentOS 6 from source

To install Python 3.8 on CentOS, you need to install OpenSSL as the one installed by CentOS from yum is very old.

cd /usr/local/src
wget https://www.openssl.org/source/openssl-1.1.1g.tar.gz
tar xvf openssl-1.1.1g.tar.gz
cd openssl-1.1.1g
./config --prefix=/usr/serverok/openssl --openssldir=/usr/serverok/openssl no-ssl2
make
make install

Now edit file

vi ~/.bash_profile

at end of the file, add

export PATH=/usr/serverok/openssl/bin:$PATH
export LD_LIBRARY_PATH=/usr/serverok/openssl/lib
export LC_ALL="en_US.UTF-8"
export LDFLAGS="-L/usr/serverok/openssl/lib -Wl,-rpath,/usr/serverok/openssl/lib"

Make the settings active with command

source ~/.bash_profile

Now we can install Python 3.8 with

cd /usr/local/src
wget https://www.python.org/ftp/python/3.8.4/Python-3.8.4.tar.xz
tar xvf Python-3.8.4.tar.xz
cd /usr/local/src/Python-3.8.4
make clean && make distclean
./configure --enable-optimizations  --with-openssl=/usr/serverok/openssl/
make altinstall

Now python 3.8 will be available in your system under /usr/local/bin

root@server12:~# python3.8 --version
Python 3.8.4
root@server12:~# which python3.8
/usr/local/bin/python3.8
root@server12:~#

July 18, 2020

yum list all available packages in a repo

To list all packages available on a specific repo, run

yum  --disablerepo="*" --enablerepo="REPO_NAME_HERE" list available

You can get list of all available repos with command

yum repolist

Example: 

yum  --disablerepo="*" --enablerepo="litespeed" list available

This command list all packages available in repo "litespeed"

April 18, 2020

Install PHP 7 on CentOS VestaCP

To install PHP 7. you need to first enable epel and remi repo.

yum install -y epel-release
rpm -Uvh http://rpms.remirepo.net/enterprise/remi-release-7.rpm

Remove existing PHP

yum -y remove php

Install PHP 7.3

yum --enablerepo=remi-php73 install php73-php php73-php-mbstring php73-php-mysqlnd php73-php-gd php73-php-fpm php73-php-intl php73-php-cli php73-php-xml php73-php-opcache php73-php-pdo php73-php-gmp php73-php-process php73-php-pecl-imagick php73-php-devel

start php-fpm

service php-fpm stop
service php73-php-fpm start

Set php 7.3 as default PHP for cli

rm /usr/bin/php
ln -s /usr/bin/php73 /usr/bin/php

Restart apache

service httpd restart

March 23, 2020

rpmdb DB_RUNRECOVERY: Fatal error, run database recovery

When running yum update on a CentOS server, i get following error.

[root@ip-172-30-0-39 ~]# yum update
error: rpmdb: BDB0113 Thread/process 12797/46913889995840 failed: BDB1507 Thread died in Berkeley DB library
error: db5 error(-30973) from dbenv->failchk: BDB0087 DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db5 -  (-30973)
error: cannot open Packages database in /var/lib/rpm
CRITICAL:yum.main:

Error: rpmdb open failed
[root@ip-172-30-0-39 ~]#

To fix it, run

rm -f /var/lib/rpm/__db.00*

March 18, 2020

rpm verify packages
To verify a package installed on system, you can use
```
rpm -V PKG_NAME
```
Example
```
[root@hello-1 curl-curl-7_69_0]# rpm -V bind
S.5....T.  c /etc/named.conf
[root@hello-1 curl-curl-7_69_0]# 
```
Here bind package have /etc/named.conf file modified.

To verify all packages on system, run
```
rpm -Va
```
Back to rpm
March 6, 2020
CentOS 7 resolv.conf make changes permanent
On rebooting the CentOS 7 server, changes made to resolv.conf is lost. This is because one of the network interface is configured to use DNS server.
```
[root@server ~]# grep DNS /etc/sysconfig/network-scripts/ifcfg-*
/etc/sysconfig/network-scripts/ifcfg-eno1:DNS1="127.0.0.1"
[root@server ~]# 
```
To fix, edit
```
vi /etc/sysconfig/network-scripts/ifcfg-eno1
```
Remove the line
```
DNS1="127.0.0.1"
```
Now NetworkManager will not modify /etc/resolv.conf file on boot.

Or you can set valid DNS servers in network config file like
```
[root@server ~]# cat /etc/sysconfig/network-scripts/ifcfg-eno1 | grep DNS
DNS1="1.1.1.1"
DNS2="8.8.8.8"
[root@server ~]# 
```
If your network configuration use DHCP, set set PEERDNS=no.
```
BOOTPROTO=dhcp
PEERDNS=no
```
Another solution is to make file immutable with
```
chattr +i /etc/resolv.conf
```
Related Posts

Domain Resolver
December 31, 2019
Install Pure-FTPd on CentOS with Virtual Users
To install Pure-FTPd on CentOS, run
```
yum install -y pure-ftpd
```
Edit configuration file
```
vi /etc/pure-ftpd/pure-ftpd.conf
```
To disable anonymous FTP, find
```
NoAnonymous                  no
```
Replace with
```
NoAnonymous                  yes
```
To enable Virtual Users, find
```
# PureDB                        /etc/pure-ftpd/pureftpd.pdb
```
Uncomment the line.
```
PureDB                        /etc/pure-ftpd/pureftpd.pdb
```
To Allow Apache user to login via FTP, find
```
MinUID                      1000
```
Replace with
```
MinUID                      47
```
I set MinUID value to 47, as apache user have UID/GID of 48. By setting MinUID below that apache user should be able to login.

Set pureftpd to start on Boot
```
systemctl enable pure-ftpd
```
Restart pure-ftpd
```
systemctl start pure-ftpd
```
Create a Virual User

To create a virtual user, run
```
pure-pw useradd  USER_NAME_HERE -u apache -g apache -d /var/www/html/
```
It will ask you to enter password two times.

Now run
```
pure-pw mkdb
systemctl restart pure-ftpd
```
Change Password of an existing Virual User
```
pure-pw passwd USER_NAME_HERE
```
It will ask you to enter new password.

Rebuild password database and restart pure-ftpd with
```
pure-pw mkdb
systemctl restart pure-ftpd
```
Related Posts

Install pureftpd on Ubuntu

pureftpd
December 30, 2019
Install vim from source on CentOS
To install vim from source on the CentOS server, run
```
yum -y install  ncurses-devel
cd /usr/local/src
wget https://github.com/vim/vim/archive/master.zip	
unzip master.zip
cd vim-master/src/
./configure
make
make install
```
This will install the latest version of Vim. You can start it with the command
```
vim
```
To get it work with “vi” command, i removed preinstalled vim editor with command
```
rpm -e --nodeps  vim-minimal
```
Now create a symlink with
```
ln -s /usr/local/bin/vim /bin/vi
```
December 29, 2019
Install clamav Antivirus on CentOS 7
ClamAV is provided by the EPEL repo. Install epel repo
```
yum install -y epel-release
```
Install ClamAV with
```
yum install clamav
```
Back to ClamAV
December 17, 2019

Category: CentOS

Setup firewall

Configure bind

Adding Domain to bind

Create a Virual User

Change Password of an existing Virual User