Category: Linux

How to install MySQL 5.7 on CentOS 7 Server
To install MySQL 5.7 on CentOS 7 server, install the repository
```
rpm -ivh http://repo.mysql.com/mysql57-community-release-el7.rpm
```
import MySQL GPG key with
```
rpm --import https://repo.mysql.com/RPM-GPG-KEY-mysql-2022
```
Install MySQL with the command
```
yum install mysql-community-server.x86_64
```
Enable MySQL to start on boot
```
systemctl enable mysqld
```
Start MySQL with
```
systemctl start mysqld
```
Find the initial MySQL password with the command
```
grep 'password' /var/log/mysqld.log
```
This initial password is expired, you should change this password before you can start using MySQL server.

To set MySQL password and secure MySQL server, run the command
```
mysql_secure_installation
```
April 4, 2022

Install CSF firewall on Ubuntu Server

First, install libwww-perl package needed for CSF firewall

apt -y install libwww-perl

Install CSF with

cd /usr/local/src
wget https://download.configserver.com/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh

Change following settings in csf.conf file

/bin/sed -i "s/RESTRICT_SYSLOG\s*=.*$/RESTRICT_SYSLOG = \"3\"/g" /etc/csf/csf.conf
/bin/sed -i "s/SYSLOG_CHECK\s*=.*$/SYSLOG_CHECK = \"3600\"/g" /etc/csf/csf.conf
/bin/sed -i "s/TESTING = \"1\"/TESTING = \"0\"/g" /etc/csf/csf.conf

If you need GUI enabled, edit file

vi /etc/csf/csf.conf

Modify following settings

UI = "1"
UI_PORT = "8282"
UI_USER = "username"
UI_PASS = "password"
UI_ALLOW = "0"

March 26, 2022

Configure VPS IP address in OneProvider Server
If you are running virtualization software like Proxmox, KVM, or VMWare ESXi on the OneProvider server, you need to order an additional IP address. On one provider IP operates in 2 modes, you need to set IP to virtualization mode to configure the IP address inside a VPS.

Go to Server Details > Manage > IP Manager

Default settings for IP address is “Host Route”, change it to “Virtualization” under Routing Type.

On this page, you can also get the Gateway IP address. All virtual machines should use the same Gateway IP as main server.

For a virtual machine, I used following netplan config
```
root@vm3:~# cat /etc/netplan/00-installer-config.yaml 
# This is the network config written by 'subiquity'
network:
  ethernets:
    enp1s0:
      dhcp4: false
      addresses:
      - 5.104.107.115/32
      nameservers:
       addresses:
       - 1.1.1.1
       - 8.8.8.8
      routes:
      - on-link: true
        to: 0.0.0.0/0
        via: 89.163.146.1
  version: 2
root@vm3:~# 
```
Here 5.104.107.115 is the IP address of the Virtual Machine. 89.163.146.1 is the gateway.

After editing file /etc/netplan/00-installer-config.yaml, you can apply the changes with command
```
netplan apply
```
March 26, 2022

Linux groups

To see lists all groups that a user is in, run

groups USER_HERE

Example

boby@sok-01:~$ groups boby
boby : boby adm cdrom sudo dip plugdev lpadmin lxd sambashare libvirt docker
boby@sok-01:~$

To add a user to a group, run

adduser USER_NAME GROUP_NAME

Example

root@vagrant:~# adduser boby sudo
Adding user `boby' to group `sudo' ...
Adding user boby to group sudo
Done.
root@vagrant:~#

To remove a user from a group

deluser USER_HERE GROUP_HERE

Example

root@vagrant:~# deluser boby sudo
Removing user `boby' from group `sudo' ...
Done.
root@vagrant:~#

March 17, 2022

Drupal 7 Enable/Disable Maintenance Mode
To disable maintenance mode in drupal 7.x run the command
```
drush vset maintenance_mode 0
```
Example
```
$ drush vset maintenance_mode 0
maintenance_mode was set to 0.   [success]
$
```
To Enable Maintenance mode, run
```
drush vset maintenance_mode 1
```
March 10, 2022
puttygen: error loading x.ppk: PuTTY key format too new
Putty saves ssh key in file with .ppk extension. To use the key on Linux systems, you need to convert it to openssh format. When converting ppk file to openssh format, i got error “PuTTY key format too new”.
```
boby@sok:~$ puttygen key.ppk -O private-openssh -o 2.pem
puttygen: error loading `key.ppk': PuTTY key format too new
boby@sok:~$
```
This error is because the puttygen command is older version. Ubuntu 20.04 comes with older version of puttygen command provided by putty-tools.

The solution is to remove putty-tools package, then install latest version of puttygen from source code.

Remove putty-tools with
```
sudo apt remove putty-tools
```
Download and install latest puttygen from

https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html

As of writing this, latest version of putty is version 0.76
```
mkdir ~/src
cd ~/src
wget https://the.earth.li/~sgtatham/putty/latest/putty-0.76.tar.gz
tar -xvf putty-0.76.tar.gz
cd putty-0.76/
./configure
make
sudo cp puttygen /usr/bin/
```
Once installed, you can check version with
```
boby@sok:~/src/putty-0.76$ puttygen --version
puttygen: Release 0.76
Build platform: 64-bit Unix
Compiler: gcc 9.3.0
Source commit: 1fd7baa7344bb38d62a024e5dba3a720c67d05cf
boby@sok:~/src/putty-0.76$ 
```
You will be able to convert newer version of ppk files to openssh format now.

See Convert PPK file to PEM
February 23, 2022
How to Migrate Linux Server with rsync
A few days ago I wanted to Migrate an Ubuntu VPS from one provider to another. I tried to take a snapshot and try to migrate, but it did not work. The VPS had few random services, so migrating services one by one was not easy. What I did was set up a new Ubuntu VPS with the same OS version, rsync files from source VPS to new VPS.

Make sure you take a backup of your server before doing it. In case anything goes wrong, you should be able to restore from back or OS reload.

Install rsync on source and destination servers.

For Ubuntu/Debian
```
apt install rsync
```
For RHEL/CentOS/AlmaLinux
```
yum install rsync
```
On the source server, create a file
```
vi /root/no_copy
```
add the following content
```
/boot/
/etc/modules
/etc/fstab
/etc/mtab
/etc/netplan/
/etc/network/
/etc/sysconfig/network-scripts/
/lib/modules
lost+found/
/sys/
/proc/
/dev/
/var/cache/
/var/log/journal/
/swapfile
/swap.img
/usr/tmpDSK
/root/.ssh/
/backup/
/home/virtfs/
```
These files won’t be copied to the new VPS. If you don’t have any other folders or files, that you don’t want to be copied to the new server, you can add to the list.

Now run rsync on the source server to copy over files to the new server
```
rsync -avzPHAX --exclude-from=/root/no_copy / root@NEW_SERVER_IP:/
```
In the command above, replace NEW_SERVER_IP with the new server IP address.

When we do rsync, all files get copied to the new server. After the first rsync run, you can run the rsync command any number of times, only changed files copied, and will finish much faster as less data need to be copied to the new server.

After the first rsync is completed, we will stop all services on the source and destination servers like MySQL, Apache, Nginx, etc… so no data gets changed while we doing the rsync. Now do another rsync, reboot the destination server, see if everything works fine.

See rsync
February 19, 2022

How To Install Apache Solr on Debian 10

Apache Solr is a highly reliable and scalable open source search platform. Solr powers the search and navigation features of many of the world’s largest internet sites.

https://solr.apache.org

Solar is based on Java, so we need to install OpenJDK

apt install -y openjdk-11-jdk-headless

Edit .bashrc file

vi ~/.bashrc

Add

export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
export PATH=$PATH:/usr/lib/jvm/java-11-openjdk-amd64/bin

Log off and log in. Alternatively, you can run

source ~/.bashrc

Next download Apache Solr binary package and install

cd /usr/local/src
wget "https://www.apache.org/dyn/closer.lua/lucene/solr/8.11.1/solr-8.11.1.tgz?action=download"
mv 'solr-8.11.1.tgz?action=download' solr-8.11.1.tgz
tar xzf solr-8.11.1.tgz solr-8.11.1/bin/install_solr_service.sh --strip-components=2
bash ./install_solr_service.sh solr-8.11.1.tgz

To start Apache Solr on boot, run

systemctl enable solr

To start Solr, run

systemctl start solr

After installation, you can access Solr admin area at

http://your-server-ip:8983

February 16, 2022

How to Install Supervisord on CentOS 7

Supervisor is a program used to monitor and control programs. It can auto startup application on server boot time, and restart if the application fails.

http://supervisord.org

To install supervisors on CentOS 7, first, enable epel repository.

yum install -y epel-release

Once EPEL repository is enabled, you can install supervisors with the yum command

yum install -y supervisor

Enable supervisord to start on boot, run

systemctl enable supervisord

Start supervisord

systemctl start supervisord

To start a python application on boot time, I created file

vi /etc/supervisord.d/telegram-bot.ini

With the following content

[program:telegram_bot]
command=/root/bots/telegram_bot/bot.py
directory=/root/bots/telegram_bot
;process_name=%(program_name)s ; process_name expr (default %(program_name)s)
numprocs=1
autostart=true
autorestart=true
stdout_logfile=/var/log/telegram-bot.log
stdout_logfile_maxbytes=1MB
stdout_logfile_backups=10
stdout_capture_maxbytes=1MB
stdout_events_enabled=false
stderr_logfile=/var/log/telegram-bot-error.log
stderr_logfile_maxbytes=1MB
stderr_logfile_backups=10
stderr_capture_maxbytes=1MB
stderr_events_enabled=false

Started application with

supervisorctl reload

See supervisord

February 16, 2022

dpkg dependency problems not removing

When removing a package, I got the following error message

root@82-165-118-245:/~# dpkg --remove psa-phpmyadmin
dpkg: dependency problems prevent removal of psa-phpmyadmin:
 plesk-core depends on psa-phpmyadmin (>= 5.1.1); however:
  Package psa-phpmyadmin is to be removed.

dpkg: error processing package psa-phpmyadmin (--remove):
 dependency problems - not removing
Errors were encountered while processing:
 psa-phpmyadmin
root@82-165-118-245:/~#

It is fixed by specifying –ignore-depends=plesk-core in apt command.

Example

root@82-165-118-245:/~# dpkg --remove --ignore-depends=plesk-core psa-phpmyadmin
(Reading database ... 168316 files and directories currently installed.)
Removing psa-phpmyadmin (5.1.1-v.ubuntu.18.04+p18.0.38.0+t210825.1032) ...
root@82-165-118-245:/~#

February 12, 2022

dpkg package pre-removal script returned error

On a Plesk server, MySQL somehow went missing. When I tried to remove a package, I get error

root@82-165-118-245:~# dpkg --remove plesk-config-troubleshooter
(Reading database ... 168528 files and directories currently installed.)
Removing plesk-config-troubleshooter (18.0-v.ubuntu.18.04+p18.0.39.2+t211117.1817) ...
dpkg action: 

ERROR while trying to detect MySQL service name

Check the error reason (see log file: /var/log/plesk/install/plesk_18.0.39_installation.log), fix and try again
dpkg action: 

ERROR while trying to detect MySQL service name


Package script failed

***** installing problem report *****
ERROR while trying to detect MySQL service name
Package script failed
dpkg: error processing package plesk-config-troubleshooter (--remove):
 installed plesk-config-troubleshooter package pre-removal script subprocess returned error exit status 1
Errors were encountered while processing:
 plesk-config-troubleshooter
root@82-165-118-245:~#

To fix this, I removed the prerm and postrm scripts. These scripts execute before and after a package is removed. It is not recommended to remove it, but if these scripts prevent you from uninstalling a package, you can remove them as the last option.

mv /var/lib/dpkg/info/plesk-config-troubleshooter.prerm ~/
mv /var/lib/dpkg/info/plesk-config-troubleshooter.postrm ~/

Or you can just edit the file, put

exit 0

somewhere before the error happens.

February 12, 2022

Cpanel find recently logged in users

To Find a list of Cpanel user logins, run

cat /usr/local/cpanel/logs/session_log | grep NEW | grep 'cpaneld' | awk '{print $1" "$6" "$8}' | tr -d '['

To see the log for a particular user, run

cat /usr/local/cpanel/logs/session_log | grep CPANEL_USER | grep NEW | grep 'cpaneld' | awk '{print $1" "$6" "$8}' | tr -d '['

In the above command, replace CPANEL_USER with the actual Cpanel username.

Back to log

February 12, 2022