Status Panel is a minimalistic open-source web application for efficient docker container management. Nothing redundant, only the most necessary features to operate your docker containers quick and easy. The software is written in Python/Flask.

GitHub: https://github.com/trydirect/status

Status Panel

Netdata is a highly scalable metrics monitoring, troubleshooting & management agent. It works in real time, collecting metrics from:

Netdata makes the metrics visualization, complex performance issues troubleshooting, and data interoperability quick and easy.

Check here what features are declared by Netdata creators:

the agent uses only 1% CPU of a single core

Netdata works with minimal disk I/O (only historical metrics written and error and access logs read).

No breaks. Netdata operates on servers of any type, edge/IoT devices, containers, and cloud deployments permanently.

No configuration and maintenance are needed.

No preparation or security measures are required for installation on your systems mid-incident.

No sudo required to install Netdata on Debian, Ubuntu, CentOS, Kubernetes, Docker, macOS, FreeBSD, and more.

Multiple operating modes: from autonomous host monitoring to central multi-host monitoring, collection, and storage.

Netdata

The web app stack deployed via TryDirect consist mainly of docker containers. Portainer is currently the most convenient tool to efficiently manage them.

You can control your machine’s Docker resources via a web interface. This means images, volumes, containers, and networks intuitive visualization.

Portainer is a universal tool in terms of the environment it works in. You can deploy it to Swarm, K8s, Azure ACI, Kubernetes (added in the 2.0 version), or Docker equally well, be that in the cloud, at the edge, or on-prem.

Portainer provides numerous governance and control tools and solutions, like:

Easy and secure deployment, management, and troubleshooting of containerized apps through a powerful GUI. Deep Kubernetes expertise is not needed.

Self-service container management system creation. You can increase your software productivity and reduce errors by building streamlined, automated workflows based on Git.

Software delivery automation with GitOPS integration.

Container environment security provision with RBAC.

These options make centralized management and multi-cluster environments security possible for the platform managers.

Portainer

phpMyAdmin is a free and open-source software tool that is easy to set up. It is created for MySQL or MariaDB database server administration and supports most database management system operations. You can manage databases, tables, columns, indexes, users, relations, permissions, and others via the intuitive web interface or directly execute any SQL statement.

phpMyAdmin has a stable and flexible codebase created by multiple contributors from the global PHP community.

CSV, SQL, XML, PDF, ISO/IEC 26300 - OpenDocument Text and Spreadsheet, Word, LATEX data export

databases, tables, fields, and indexes maintenance, creation, browsing, copying, dropping, remaining and altering

SQL-statement, incl. even batch-queries execution, edition, and bookmark

MySQL user accounts and privileges management

stored procedures and triggers management

Query-by-example (QBE) complex queries creation

For security purposes, TryDirect recommends that you first stop (pause) the phpMyAdmin container and then start it as necessary. This can be done by using Portainer or the Status Panel.

Deploy LAMP stack with phpMyAdmin included for free

phpMyAdmin

Web tools

It is important to be able to find out your server's public IP address right from the terminal while working on remote server

Check the article below, to learn how to discover your system or Server's Public IP address from the Terminal on Linux.

Нou can find your server's public IP address y using the host command:

host myip.opendns.com resolver1.opendns.com

Using domain server:
Name: resolver1.opendns.com
Address: 2620:119:35::35#53
Aliases:

myip.opendns.com has IPv6 address 2400:6180:100:d0::8e9:c001

If you want to get an IPv4 address using the host command, you can add the “-4” option to it.

host -4 myip.opendns.com resolver1.opendns.com

Using domain server:
Name: resolver1.opendns.com
Address: 208.67.222.222#53
Aliases:

myip.opendns.com has address 143.110.250.111

You can use the grep command to filter only IPv6/IPv4 by running the following command:

host -4 myip.opendns.com resolver1.opendns.com | grep "address" | awk 'NF>1{print $NF}'

host -6 myip.opendns.com resolver1.opendns.com | grep "address" | awk 'NF>1{print $NF}'

The dig command is one of the easiest methods to find the public IP address of your server.

You can execute any of the commands below to find your system IP address.

dig ANY +short myip.opendns.com @resolver1.opendns.com

dig ANY +short @resolver2.opendns.com myip.opendns.com

dig +short ANY whoami.akamai.net @ns1-1.akamaitech.net

dig +short @ns1-1.akamaitech.net ANY whoami.akamai.net

dig +short ANY o-o.myaddr.l.google.com @ns1.google.com

You can specify the IP version as shown in the below example:

dig +short ANY o-o.myaddr.l.google.com @ns1.google.com -4

Kindly note that you can use the "-4" option with dig for IPv4 and the "-6" option  for IPv6 in case you want to get a specific IP version.

Wget is a powerful command-line downloader available on most Linux distributions. The wget command allows you to find the public IP address of your system by using it with third-party websites, as shown below:

wget -qO- http://ipecho.net/plain | xargs echo

wget -qO- https://ifconfig.me | xargs echo

Just like the wget commands, you can use the curl command with a third-party service to find the public IP address of your system.

Below are some third-party services you can use with the curl command:

Congratulations! Now you can easily discover your system's public IP address using Terminal on Linux. Do we miss something useful?  Send it to us, use the contact us form.

Ho to find out your server's public IP address right from the terminal 

Find the public IP address from the terminal

Simple Firewall  - is a set of iptables rules that deny SSH access to everybody except the network range IP’s defined in the text field below. Let’s call it Admin’s IP. By default, the admin's IP is detected automatically and the range is calculated based on it. Most Linux distributions have pre-installed iptables, which means Simple Firewall will not install any additional software packages on the user’s server.

Attackers' activity is usually rising right after a new VPS server is created. They often look for web applications with default admin credentials, unfinished setups, admin tools, open ports and so on. “Simple Firewall” rules were implemented and offered to protect the newly created server from various attacks like brute force attacks.

TryDirect also offers administration tools for server management purposes: Status Panel, Portainer, and Monitoring tools like Netdata, PHPMyAdmin.

Even administration tools are password-protected. This enables the“Simple Firewall'' feature to make administration tools accessible only from the specified admin's IP network. Disabling “Simple Firewall” makes admin login form public, visible for all.

Admin’s IP range can be changed to any other IP address range (e.g. 1.1.1.0/24).

Simple Firewall

tcpdump - is a network packet sniffer which can capture or filter any type of traffic like TCP, UDP, and ICMP. It is a widely used command-line tool for network monitoring and debugging. tcpdump is installed by default on many Unix/Linux distributions.

Using tcpdump, you can capture live traffic and save that data to the file for future analysis. tcpdump saves the file in pcap format, which can be read by the tcpdump command or GUI tools like Wireshark.

tcpdump is used for checking system security, Penetration testing, network troubleshooting, and many more. In short, tcpdump is a Swiss army knife for any system administrator, network engineer, or security professional.

This guide will teach you some basics and practical examples of the tcpdump command.

You should always run the tcpdump command with the root user. The tcpdump command continues to run until you press Ctrl+C to terminate it.

The following is the tcpdump command syntax in short:

When you run tcpdump with no filters, it will show you all the packets flowing through the default interface.

You can list all the interfaces of your server by running the following command:

1.eth0 [Up, Running]
2.eth1 [Up, Running]
3.lo [Up, Running, Loopback]
4.any (Pseudo-device that captures on all interfaces) [Up, Running]
5.bluetooth-monitor (Bluetooth Linux Monitor) [none]
6.nflog (Linux netfilter log (NFLOG) interface) [none]
7.nfqueue (Linux netfilter queue (NFQUEUE) interface) [none]

You can capture all packets from all interfaces by using any interface:

For better understanding, You should use the interface name using the -i option:

For more detailed output, you can use the -v or -vv options:

You can limit the tcpdump command output using the below command:

By default, tcpdump does the DNS resolution. You can disable name resolution by using the option -n and port resolution with -nn:

This option is very useful while troubleshooting network issues.

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked v1), capture size 262144 bytes
14:56:10.085238 IP 172.18.1.48.22 > 172.18.1.250.59860: Flags [P.], seq 475071168:475071392, ack 2781200040, win 501, length 224
14:56:10.085526 IP 172.18.1.48.22 > 172.18.1.250.59860: Flags [P.], seq 224:416, ack 1, win 501, length 192
14:56:10.085631 IP 172.18.1.48.22 > 172.18.1.250.59860: Flags [P.], seq 416:576, ack 1, win 501, length 160
14:56:10.085760 IP 172.18.1.48.22 > 172.18.1.250.59860: Flags [P.], seq 576:736, ack 1, win 501, length 160
14:56:10.085860 IP 172.18.1.48.22 > 172.18.1.250.59860: Flags [P.], seq 736:896, ack 1, win 501, length 160
5 packets captured
5 packets received by filter
0 packets dropped by kernel

You can capture packets with properly readable timestamps using the tcpdump -tttt option:

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked v1), capture size 262144 bytes
2022-03-27 15:20:25.081838 IP 172.18.1.48.22 > 172.18.1.250.50472: Flags [P.], seq 3309433839:3309434063, ack 2385369981, win 501, length 224
2022-03-27 15:20:25.082165 IP 172.18.1.48.22 > 172.18.1.250.50472: Flags [P.], seq 224:432, ack 1, win 501, length 208
2022-03-27 15:20:25.082350 IP 172.18.1.48.22 > 172.18.1.250.50472: Flags [P.], seq 432:608, ack 1, win 501, length 176
3 packets captured
3 packets received by filter
0 packets dropped by kernel

tcpdump prints output in one line for each packet. Its syntax looks like this:

[Timestamp] [Protocol] [Src IP].[Src Port] > [Dst IP].[Dst Port]: [Flags], [Seq], [Ack], [Win Size], [Options], [Data Length]

When you type the tcpdump command, you will get output as shown in the below example:

18:13:17.425434 IP app.4436 > 157.32.66.94.45896: Flags [P.], seq 696:749, ack 632, win 3372, options [nop,nop,TS val 2489039195 ecr 16819361], length 53

18:13:17.425434: It is the timestamp of the captured packet as per the system timezone.

app.4436: hostname or IP with port number, separated by a dot (.).

157.35.66.94.45896: destination hostname or IP and port number, separated by a dot (.).

Flags [P.]: It is TCP Flags. It shows the state of the connection. In this example, [P.] means Push Acknowledgment packet.

win 3372: It means the number of available bytes in the receiving buffer.

options [nop,nop,TS val 2489039195 ecr 16819361]: TCP options.

length 53: The length of the data payload.

Using tcpdump Filters, you can find exactly what you are looking for. For example, when troubleshooting issues related to an FTP server, you can use filters to get only FTP traffic. Filters give you a clear idea of what exactly is going on on your server. The most used tcpdump filters are: port, protocol, host, src, dst, tcp, udp, icmp.

You can filter packets using a service name or port with the port filter. For example, you want to capture packets related to the SSH service:

12:12:59.283525 IP 139.59.3.60.22 > 182.77.112.118.62155: Flags [P.], seq 857071566:857071754, ack 3442378916, win 501, options [nop,nop,TS val 2380853868 ecr 2857908344], length 188
12:12:59.283669 IP 139.59.3.60.22 > 182.77.112.118.62155: Flags [P.], seq 188:408, ack 1, win 501, options [nop,nop,TS val 2380853868 ecr 2857908344], length 220
12:12:59.283698 IP 139.59.3.60.22 > 182.77.112.118.62155: Flags [P.], seq 408:612, ack 1, win 501, options [nop,nop,TS val 2380853868 ecr 2857908344], length 204
12:12:59.283724 IP 139.59.3.60.22 > 182.77.112.118.62155: Flags [P.], seq 612:816, ack 1, win 501, options [nop,nop,TS val 2380853868 ecr 2857908344], length 204
12:12:59.283748 IP 139.59.3.60.22 > 182.77.112.118.62155: Flags [P.], seq 816:1020, ack 1, win 501, options [nop,nop,TS val 2380853868 ecr 2857908344], length 204
5 packets captured
6 packets received by filter
0 packets dropped by kernel

You can also capture packets between port ranges as shown below:

Occasionally, you may want to capture all the packages, EXCEPT some specific port. For example, you would like to monitor all the traffic on the server but do not want to capture the port 22:

Alternatively, you can find DNS traffic using the port number, as shown in the below example:

To find FTP traffic by name, execute the below command on your FTP server:

Using protocol with the tcpdump command, you can only get packets related to a specific protocol. For example, if you want to capture only ICMP packets, then run the following command on your server:

Next, ping your server from another system:

You will see the below output on your server:

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked v1), capture size 262144 bytes
12:22:39.353266 IP 192.168.1.52 > 192.168.1.52: ICMP echo request, id 4, seq 18, length 64
12:22:39.353292 IP 192.168.1.52 > 192.168.1.52: ICMP echo reply, id 4, seq 18, length 64
12:22:40.377322 IP 192.168.1.52 > 192.168.1.52: ICMP echo request, id 4, seq 19, length 64
12:22:40.377347 IP 192.168.1.52 > 192.168.1.52: ICMP echo reply, id 4, seq 19, length 64

To filter traffic for a specific host, you can use host filter along with the tcpdump command:

You can combine filters using the and (&&), or (||), and not (!) operators.

The below example shows your destination with a port filter. It captures traffic from 192.168.1.66 on port 80 or on port 443:

tcpdump -n -nn -c 3 -i any 'dst 192.168.1.66 and (tcp port 80 or tcp port 443)'

So far, you have seen how to use the tcpdump command at a basic level. Now let's see some practical and useful tcpdump commands:

4.1. Capture All incoming HTTP GET traffic requests

tcpdump -i any -s 0 -nn -A 'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420'

The above command will give GET traffic requests. Here 0x47455420 is the ASCII value for GET request.

11:22:29.789727 IP 172.77.112.118.62461 > 139.65.3.60.19999: Flags [P.], seq 1724:2155, ack 2149, win 501, options [nop,nop,TS val 1165783811 ecr 2464213374], length 431
E.....@.8..-.Mpv.;.<..N.._.=...............
E|s....~GET /api/v1/alarms?active&_=1648528027188 HTTP/1.1
Host: 139.65.3.60:19999
Connection: keep-alive
Accept: */*
Pragma: no-cache
Cache-Control: no-cache, no-store
X-Requested-With: XMLHttpRequest
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36
Referer: http://139.65.3.60:19999/
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9,gu;q=0.8

4.2. Capture All incoming HTTP POST requests:

Same as above command. You can find post requests by executing the following command:

tcpdump -i any -s 0 -A 'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x504F5354'

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked v1), capture size 262144 bytes

11:30:55.534062 IP app.53364 > 169.252.159.254.http: Flags [P.], seq 1904543180:1904544302, ack 3887682708, win 502, options [nop,nop,TS val 2447752694 ecr 3070714564], length 1122: HTTP: POST /v1/metrics/droplet_id/238459262 HTTP/1.1
E.....@.@.o%.;.<.....t.Pq.....T............
......b.POST /v1/metrics/droplet_id/238459262 HTTP/1.1
Host: 169.252.159.254
User-Agent: do-agent-3.13.0
Content-Length: 848
Content-Type: application/timeseries-binary-0
X-Auth-Key: 21705a51d80d4b87883dbce1f90b742ffd53847d0bfbe38b
Accept-Encoding: gzip
Connection: close

....sNaPpY.B...~....,..sonar_disk...cards_completed_total.device.vda.:.....@.memory./...1D.B.6$.(swap_cached.).....@.6*. available.........B.6(..R ........B'.)Pnetwork_receive_bytes...eth1.8.$C../B..98cpu.mode.system.' ..(\O!.@0.'.d=?0_time_seconds..fA..?.B.file d._size.2./dev/vda1.fstype.ext4.mountpoint./.......i_SB..Q.load.. .z..G..?%....8sectors_written.s6...V...A.T..5.p )\...(.?..TM.F......B.6%..free.H....*.AQK5s.irq.....Q!.$.soft.(.{...T.@..o.(.teal.J.&...@2..!..e... ...Qhp.@,.f%N.@.;...<.YA..>%.5V.
..p=
.?..-VE..f:6.....B-.F...die..ed5.i.f...".?.Q..readV4.....^A+.4..,..... ..A(.=q..transmitB...01....J...>B.:.U. .. ..D.B$.tpdiagnostic.error.flush failur2....@`@..6UD.n.....q=
...}@2..!..B...j.t..K@J..%.-......O-CB..xbuild_info.revision.72c8c9b.ver...3.13.=g....u....id......i.~rAB...user.@...l.yB.A.}....5...:F}..iowait.\,.........J.@

4.3. Capture HTTP traffic including request and response headers and message body on port 443:

tcpdump -A -s 0 'tcp port 443 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'

tcpdump

How to check whether your server is online using a Linux command line.

We often need to check connectivity to troubleshoot network issues or want to check whether our server is online. We created this article to show you how to do this.

There are many handy Linux tools for this:

Ping is one of the most widely used commands to check whether a server or remote host is up and responding. Ping sends ICMP ECHO_REQUEST to the server.

If ICMP is blocked from the server-side or cloud provider, then the ping command may not work as expected (like AWS ec2 instance).

Here, we assume that cloud provider's firewalls do not block ICMP.

➜  ~ ping example.com
PING example.com (93.184.216.34): 56 data bytes
64 bytes from 93.184.216.34: icmp_seq=0 ttl=53 time=129.615 ms
64 bytes from 93.184.216.34: icmp_seq=1 ttl=53 time=130.620 ms
^C
--- example.com ping statistics ---
2 packets transmitted, 2 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 129.615/130.118/130.620/0.502 ms

Telnet is a network protocol that allows you to connect to a remote host. Telnet is usually installed on most Linux OS by default. Otherwise, you can run the following command in the terminal:

Using telnet, you can identify the availability of certain ports. You can use telnet to make sure no firewalls in between are blocking incoming connections to the server.

System or network administrators use Telnet to configure network devices like routers and switches.

➜  ~ telnet example.com 22
Trying 111.201.251.32...
Connected to example.com.
Escape character is '^]'.
SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.5

The above command shows that port 22 is open on the example.com.

Let’s now check whether the webserver port is open.

➜  ~ telnet example.com 443
Trying 93.184.216.34...
Connected to example.com.
Escape character is '^]'.


Which means the port 443 is open and accessible.

If the port is firewalled  on the remote host, then you will see something like this

➜  ~ telnet example.com 22
Trying 93.184.216.34...
telnet: connect to address 93.184.216.34: Operation timed out
Trying 2606:2800:220:1:248:1893:25c8:1946...
telnet: connect to address 2606:2800:220:1:248:1893:25c8:1946: No route to host
telnet: Unable to connect to remote host

Simply speaking, nslookup is used for DNS record checks. You can use nslookup to check if your website is connected to the internet. It is also used to troubleshoot DNS-related problems.

➜  ~ nslookup example.com
Server:		8.8.8.8
Address:	8.8.8.8#53

Non-authoritative answer:
Name:	example.com
Address: 93.184.216.34


It will show the IP address and other details

➜  ~ nslookup example.com1
Server:		8.8.8.8
Address:	8.8.8.8#53

** server can't find example.com1: NXDOMAIN

By default, nslookup command output shows A records of a domain.

Nmap or Network Mapper is a powerful tool for finding open ports and network audits.

In case the nmap command  is not available, you can install it executing the following command in terminal:

Nmap is also used to identify whether the host is up or not.

This command will show open port and host status as below:

➜  ~ nmap example.com
Starting Nmap 7.92 ( https://nmap.org ) at 2022-03-15 12:36 EET
Nmap scan report for example.com (93.184.216.34)
Host is up (0.13s latency).
Not shown: 996 filtered tcp ports (no-response)
PORT     STATE  SERVICE
80/tcp   open   http
443/tcp  open   https
1119/tcp closed bnetgame
1935/tcp closed rtmp

Nmap done: 1 IP address (1 host up) scanned in 64.63 seconds

You can easily check whether your server is running using the following command:

➜  ~ nmap -sn example.com
Starting Nmap 7.92 ( https://nmap.org ) at 2022-03-15 12:39 EET
Nmap scan report for example.com (93.184.216.34)
Host is up (0.13s latency).
Nmap done: 1 IP address (1 host up) scanned in 0.23 seconds

Netcat is known as an nc command used for network scanning like Port Scanning, open Remote connections, Network debugging, read and write operation on the network, and many more.

You can easily check the reachability of remote ports using nc Command.

If port 443 is running on the server, we will get the following:

➜  ~ nc -vz example.com 443
Connection to example.com port 443 [tcp/https] succeeded!

Wget is a command-line download tool that supports HTTP, HTTPS and FTP. Wget is very useful for those who want to check any network-related issue or test connection from a Linux terminal. It will help you in web-related issues debugging.

➜  ~ wget example.com
--2022-03-15 12:42:10--  http://example.com/
Resolving example.com (example.com)... 93.184.216.34
Connecting to example.com (example.com)|93.184.216.34|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1256 (1.2K) [text/html]
Saving to: ‘index.html’

index.html                      100%[=====================================================>]   1.23K  --.-KB/s    in 0s

2022-03-15 12:42:10 (120 MB/s) - ‘index.html’ saved [1256/1256]

➜  ~

Here we get the “200” response code from the web server and index.html file downloaded.

You can use the curl command to transfer data either from or to a server. It supports proxy support, user authentication, FTP upload, HTTP post, SSL connections, cookies, and many more.

You can use curl command to test TCP ports connectivity.

Let’s check SSH port connection to a temporary created demo server with CURL

➜  ~ curl -v telnet://example2.com:22
*   Trying 93.184.216.35:22...
* Connected to example2.com (93.184.216.35) port 22 (#0)
SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.5

Now let’s check whether our web server is running on port 80 using curl.  -I option will show only headers in the output

curl -I example.com
HTTP/1.1 200 OK
Content-Encoding: gzip
Accept-Ranges: bytes
Age: 476807
Cache-Control: max-age=604800
Content-Type: text/html; charset=UTF-8
Date: Tue, 15 Mar 2022 10:48:07 GMT
Etag: "3147526947+ident"
Expires: Tue, 22 Mar 2022 10:48:07 GMT
Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
Server: ECS (nyb/1D13)
X-Cache: HIT
Content-Length: 648

~ curl -v telnet://example.com:25
*   Trying 93.184.216.34:25...
* connect to 93.184.216.34 port 25 failed: Operation timed out
* Failed to connect to example.com port 25: Operation timed out
* Closing connection 0
curl: (28) Failed to connect to example.com port 25: Operation timed out

As you see, CURL is a useful command-line tool available in Linux to check the connection with the server and port.

We’ve examined the Linux command-line tools for checking server health and network connectivity in detail. These are the must-know tools for all the system and network administrators any network-related issues.

DNS propagation is the time frame in which DNS modifications are being renewed over the Internet. Modifying DNS records (such as swapping the IP address specified for a particular hostname) typically takes some considerable time. It can take up to 72 hours before propagating globally. These DNS propagation times are awkward or simply inadmissible in several modern use cases.

If an IP address or other knowledge about a hostname is added or modified in a DNS record, the change must be applied to all systems in the world competing in the DNS process. When a customer completes a DNS query and reaches a system where changes have not yet been generated, the user gets the old address. That indicates the change has not propagated to that user.

There is one issue with DNS propagation. It is effective and, at the same time, one of the weakest sections. Propagation is not complete as long as you have a vast global series of DNS servers and local DNS resolvers, and a part of the chain controls the existing DNS information.

Propagation is a problem but not that intractable. Next-generation DNS base can reduce DNS propagation period from days or hours to seconds.

Why does DNS propagation take so long? Three factors affecting propagation time:

TTL is a period of time for which a query is stored in the cache of your local system or remote DNS server before the DNS resolver can request a new one. At the end of this period, DNS data from the local system is replaced by updated information, newly gathered by the DNS resolver. The lower the TTL, the quicker the propagation rate.

For example, the TTL is set to be 60 minutes. The servers in the system will continue to use old information for an hour, and it will be shown to all the website visitors in this period. Then, the local server will delete this data and create a new DNS request to get the updated information flow.

ISPs cache DNS records to provide users immediate access to their websites. They make one DNS lookup for all websites and use the outcomes for several users as practicable. Some ISPs neglect the TTL perspective and keep DNS records in the cache even if the TTL period has previously expired. This extends the propagation time.

If you change the commanding name server for your website (the DNS server that holds the official and accurate data about your web address), these changes must reflect higher up in the DNS authority. For example, if the website’s TLD extension is ".com", the name server changes will need to be updated on top-level domain (TLD) name servers. Propagation of this change can take a long time, as the root server can have a TTL of 48 hours or more to prevent abuse.

How can you check your DNS using Linux Terminal codes?

There are several websites where you can check your domain's DNS.

You can check the domain DNS information from your Linux machine using three commands.

1. How to check DNS using the dig command


The dig command is an abbreviation for "Domain Information Grover" This is a manageable tool for checking DNS name servers. It performs a DNS lookup and represents the result reflected from the queried name server.

Most DNS controllers used the dig command to resolve DNS problems because of their versatility, comfort of use, and precision in output. Other lookup tools tend to be less functional than digging.

; <<>> DiG 9.10.6 <<>> google.com ANY +noall +answer

google.com.  274 IN AAAA 2a00:1450:4001:811::200e

google.com.  3574 IN TXT "facebook-domain-verification=22rm551cu4k0ab0bxsw536tlds4h95"

google.com.  574 IN MX 40 alt3.aspmx.l.google.com.

google.com.  574 IN MX 30 alt2.aspmx.l.google.com.

google.com.  3574 IN TXT "google-site-verification=TV9-DBe4R80X4v0M4U_bd_J9cpOJM0nikft0jAgjmsQ"

google.com.  3574 IN TXT "globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8="

google.com.  3574 IN TXT "google-site-verification=wD8N7i1JTNTkezJ49swvWW48f8_9xveREV4oB-0Hf5o"

google.com.  34 IN SOA ns1.google.com. dns-admin.google.com. 433718347 900 900 1800 60

google.com.  3574 IN TXT "docusign=1b0a6754-49b1-4db5-8540-d2c12664b289"

google.com.  3574 IN TXT "MS=E4A68B9AB2BB9670BCE15412F62916164C0B20BB"

google.com.  21574 IN CAA 0 issue "pki.goog"

google.com.  3574 IN TXT "v=spf1 include:_spf.google.com ~all"

google.com.  3574 IN TXT "docusign=05958488-4752-4ef2-95eb-aa7ba8a3bd0e"

DNS propagation is a very good thing, yeah

Dashboard

TryDirect explains

Web tools

LINUX/UNIX CLI