protocol

Dovecot: Fatal: Error in configuration file /etc/dovecot/dovecot.conf: protocols: Unknown protocol: sieve

1.0 Error:

While configuring the Dovecot Mail Delivery Agent, the Dovecot server would not start and the following error messages were printed.

$ sudo systemctl start dovecot
Job for dovecot.service failed because the control process exited with error code. See "systemctl status dovecot.service" and "journalctl -xe" for details.
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ss command in Linux

1. ss command

The ss command gives the socket statistics. It gives information about the network connections. ss is a replacement for the netstat command.

By default, the ss command gives information about non-listening sockets.

$ ss
Netid  State      Recv-Q Send-Q   Local Address:Port       Peer Address:Port
u_str  ESTAB      0      0                    * 4482                  * 4481
u_str  ESTAB      0      0                    * 4285                  * 3631
...
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Manage network

ip command in Linux

1.0 INTRODUCTION

The iproute2 package contains utilities for network and traffic control. The major commands in iproute2 package are the ip command for IPV4 and IPV6 configuration and tc for traffic control. These commands replace the older ifconfig and the route commands of the net-tools package.… Read more

netstat

1. netstat command

The netstat command in Linux provides network statistics and information about the networking subsystem. It gives information about network connections, routing tables and network interface statistics. For example,

$ netstat
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 myhost.local:53744      mail.example.i:imaps    ESTABLISHED
tcp        0      0 myhost.local:36149      example.com:http        ESTABLISHED
tcp        0      0 myhost.local:57051      imap.example.n:imap2    ESTABLISHED
tcp        0      0 myhost.local:51209      mail.example.i:imaps    ESTABLISHED
tcp        0      0 myhost.local:35617      example.com:http        ESTABLISHED
tcp        0      0 myhost.local:51207      mail.example.i:imaps    ESTABLISHED
tcp        0      0 myhost.local:52281      r-198-51-100-12.tw:http ESTABLISHED
tcp        0      0 myhost.local:51208      mail.example.i:imaps    ESTABLISHED
tcp        0      0 myhost.local:52282      r-198-51-100-12.tw:http TIME_WAIT
...
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Routing in Linux

In Internet, the Internet Protocol (IP) is at the Network Layer, which is the third layer of the ISO reference model of network architecture. IP deals with IP packets or datagrams, which are the basic transfer units in the Internet and the higher level protocols like UDP and TCP are built on top of IP datagrams.… Read more

NTP

Synchronize your computer’s clock using the NTP

Coordinated Universal Time

The Coordinated Universal Time (UTC) is the universally accepted time standard based on atomic clocks with leap seconds added judiciously to keep it in tune with the traditional solar time. The UTC is available as standard from designated national measurement institutes (NMIs) in most countries.… Read more