Digitalocean – Page 12

April 24, 2020 by dev Leave a Comment

Dovecot Mail Service In Linux – Start, Stop, Restart, Reload, Status, Enable

Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like systems.

Start:

service dovecot start

systemctl start dovecot

Stop:

service dovecot stop

systemctl stop dovecot

Restart:

service dovecot restart

systemctl restart dovecot

Reload:

service dovecot reload

systemctl reload dovecot

Status:

service dovecot status

systemctl status dovecot

Enable Dovecot Mail Service on Boot

chkconfig dovecot on

systemctl enable dovecot

Dovecot default configuration file location
```
vi /etc/dovecot/dovecot.conf
```

April 23, 2020 by dev Leave a Comment

DirectAdmin email issues and solutions.

The service ‘exim’ on server xxx is currently down [Follow this]

SMTP Error (-1): Connection to server failed.

Check SSL certificate
Check email server
```
service postfix status
```
Unit postfix.service could not be found? Restart postfix
```
service postfix restart
```
Failed to restart postfix.service: Unit postfix.service not found. [Follow this]

April 23, 2020 by dev 1 Comment

The service ‘exim’ on server xxx is currently down

Rebuild your exim.

cd /usr/local/directadmin/custombuild
./build update
./build set exim yes
./build set eximconf yes
./build set eximconf_release 4.5
./build set spamassassin yes
./build update
./build exim
./build exim_conf

Start, stop and restart the Exim mail server

Start Services:

/etc/init.d/exim start

service exim start

Stop Services:

/etc/init.d/exim stop

service exim stop

Restart Services

/etc/init.d/exim restart

service exim restart

Status of Exim service:

/etc/init.d/exim status

service exim status

systemctl status exim.service

Edit exim conf

vi /etc/exim.conf

Helpfiles for Exim

https://help.directadmin.com/?topic=17

April 16, 2020 by dev Leave a Comment

Fdisk command line in Linux to help to manage partitions

fdisk command line utility is used to view and manage hard disks and partitions on Linux systems.

Commonly used fdisk commands.

n – Create partition
p – print partition table
d – delete a partition
q – exit without saving the changes
w – write the changes and exit.

Display disk cylinders | View all existing disk partitions | command to list the partitions | View all Disk Partitions in Linux | List Partitions
```
fdisk -l
```
View partitions of a specific hard disk (for example, vda)
```
fdisk -l /dev/vda
```
To get more information detailed and size readable by human of a specific hard disk.
```
partx -s /dev/vda
```
Delete a hard disk partition
If you would like to combine several partitions (for example, /dev/vda2 and /dev/vda3) into a single disk partition, you have to first delete all those individual partitions, as shown below.
```
fdisk /dev/vda
```
Then
```
Command (m for help): p
```
Then
```
Command (m for help): d
```
Then
```
Partition number (1-5): 3
```
Then
```
Command (m for help): d
```
Then
```
Partition number (1-5): 2
```
Then
```
Command (m for help): w
```
Create a new disk partition
```
fdisk /dev/sda
```
```
Command (m for help): n
```

April 15, 2020 by dev Leave a Comment

How to restrict direct root access | Linux | CentOS

We can do it just in two steps.

Step One:

At first we will create new root user as follows (for example, newroot)

Login as root using SSH.
Create new user e.g., newroot and add user to wheel group
```
useradd -G wheel newroot
```
Set password for newroot
```
passwd newroot
```
You will get option to enter password. Use letter and number only.
Save the newroot and password somewhere of you edge.
Su to newroot
```
su - newroot
```
Test sudo permission (permission should be root)
```
sudo whoami
```
Enter password of newroot and it will show result “root”.
Open sshd config file and check whether it has the “newroot” in AllowUsers. If not, add the user manually. (usually at the end).
```
vi /etc/ssh/sshd_config
```
[Permission Denied!] Quit :q
```
AllowUsers newroot
```
Restart sshd.service
```
sudo systemctl restart sshd.service
```

Step Two:

Now we are going to disable the root user. Before doing this, you have to logout from “root” and then login with “newroot”.

You can only disable the “root”, if you can successfully login with “newroot”.

After successfully login with “newroot”, su to “root” using root password.
```
su - root
```
Then open sshd_config.
```
vi /etc/ssh/sshd_config
```
Search and change permitRootLogin “yes” to “no” as follows.
```
permitRootLogin no
```
Restart sshd.service to implement the change
```
sudo systemctl restart sshd.service
```
Now logout from “newroot” and try to login “root”
Login with root now not allowed. Access Deny.
So login with “newroot” and then su to root with root password
```
su - root
```