Linux Networking





The variety of Linux distributions creates myriad issues relating to configuration and operations when computers are networked, not the least of which is the use of various network management applications, some of which are included with specific distributions, while others are standalone applications.

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Portable, direct connect server access
Portable, direct connect server access

The ATEN CV211 connects a laptop directly to any server allowing you instant access to perform data maintenance and local operations, for quick troubleshooting, updating, service and repair.


How to expand putty to full screen?

also i hae 20 server instances configured  named connection1, connection2 etc till connection20

when i connect it should say connection1 at the top than meaningless ip address etc at the top  of putty window. can i configure somewhere to do that?

also how to change text and background colors. please advise
what is difference between below commands

$ cd xyz

it says no such file or directory

$ cd /xyz
says no such file or directory

where as when i say

$ cd /xyz/
it goes to xyz directory though

what is use or importance of /  and / at the beginning and end?

please advise

Ubuntu 14.04 Desktop I usually connect to Internet via PPPoE over Wi-Fi signal from my router. The router gets the Internet from Ethernet cable which comes from my ISP into my apartment. So it's not a regular Wi-Fi Internet, WLAN just connects my computer to WIRED PPPoE I get from the ISP. Sometimes what happens is that Internet stops working and wireless signal in Ubuntu keeps disconnecting and then reconnecting by itself. And pppoeconf command can't finf PPPoE over wlan0. Then I have to connect the cable directly to my computer's RJ-45 and re-do pppoeconf and then it finds PPPoE over eth0 and then I get Internet. The problem is that for some strange reason, it works better when I use the former option, i.e. connect the cable to the router and use the wireless signal to connect to the PC. I just don't know how to fix this issue with my Wi-Fi.
Hello, I'm curious, hence I ask you; Is there such a "recent college engineer", either software or hardware, or one that studied both, who would meet all of these requirements:
embedded Linux based data telecommunications system/ VoIP/SIP
satellite network application and
embedded software/ Firmware/embedded systems
automation scripting
Linux operating system/Linux Network expertise
Unix shell scripting
WEB GUI test automation
DO-178B experience
Satellite communication experience
Telecommunication experience/PBX switching systems

Any comments?
Do companies expect to find an "expert" engineer with all this knowledge?
I have a CentOS 7 (7.3.1611 ) server running Gnome (3.14.2) and using xRDP (0.9.2-12.el7.x86_64) and authenticating via radius to DUO. I RDP (10.2) from Windows 10. This all work fine.

My problem is when the session locks or time out I can’t log back in unless I have a local password set which I don’t want to do. I want the auth to continuously go through radius/Duo.

My questions are:
1.      How or where do I point re-login to radius?
2.      Or when session times out to kill session so they have to re-auth through radius?
3.      How do I extend the session time out?

# systemctl start dhcpd
Job for dhcpd.service failed because the control process exited with error code. Se e "systemctl status dhcpd.service" and "journalctl -xe" for details.
Hi experts

Require script to capture all root logins, through su - or direct login with root.

OS - CentOS 7
I am trying to sync the following repos.

I created a repo in satellite and when I tried to sync its not downloading any packages. I see the meta data processing message came up and suddenly it went to 100% .  I don't see any packages downloaded.

We have configured a new server in datacenter and everything looks good, but I can't seems to ping from same VLAN,

When I do Arp,

 arp  -a
server1 ( at <incomplete> on eth0

incomplete mean,  switch doesn't have the MAC address of the device?
WordPress Tutorial 1: Installation & Setup
WordPress Tutorial 1: Installation & Setup

WordPress is a very popular option for running your web site and can be used to get your content online quickly for the world to see. This guide will walk you through installing the WordPress server software and the initial setup process.


In putty vi editor vi unix how to see later pages and change colors for bettwer view.

i open big property file not able to see what is at bottom.

how to search in vi editor for some text sat xyz.

setting i went i changed colors , font etc not reflecting.

what is best setting to give for better view

when i opened in vi
it says 536L, 28390C
what is L what is C
how to know how many lines there how many it is showing etc
can i use winscp free version for production servers viewing property files?
please advise

I am fed up with putty with basic options.

Any better tools or IDEs to check logs or to grep unix/linux boxes.

Where  i can download secure ftp and how much is fees?
any advanced putty IDE there
any good free IDE accepted by industry.

please advise
In my server i have two nics, eth0 that's a dedicated interface and eth1 that's has configured as trunk on my vmware.
In eth1 I need to create multiple vlan's, i was able to do it but I cant redirect the traffics between each vlan.
The gateway of this vlan is
When I do ping -I return unreachable network, seams that miss some rute.
Best regards
Dear Experts,

How to copy or transfer a file from one Linux server to multiple Linux server in same network from a single cmd or script ? It should be a single line cmd for copy my file to multipal servers, don't want to use separate line for every server.

for example:
scp report_zonal

i dont know it is possible or any other way to make it possible, please suggest

Currently i am using this method, it is working also, but i don't want to use this process.

[root@200 ftp]# cat
# transfer file to server
cd /root/
#DC Zonal
scp report_zonal
scp report_zonal
scp report_zonal
scp report_zonal
what the heck is delta rpm and why use it , cant I just update or upgrade with yum update or something like that ?

Hi All!!

Is it possible to isolate a small linux box computer from the rest of my home network but still have internet capabilities. My home network connects to a single router which has various devices connected to it, such as Windows machines and other devices (not many but some).

The ideas is, if the linux PC or other devices are compromised, it will not affect the others. I would also like to to port-forward the linux box for remote use. So by isolating it from the network i can minimise the risks if any.

I understand that the likelihood of Linux devices infecting Windows (or vice versa) is rare but I'd still like to achieve this.

After doing research, i have come up with the below...

  • Installing/Configuring A/V on the Linux Terminal
  • Using IPtables to restrict other devices accessing. - Complete newbie to this but would appreciate some guidance.
  • Different IP Subnets.

I would very much appreciate it if someone would be able to assist me in understanding and designing a solution.

Thank you!!
I have two laptops, one with Windows 10 where the USB dongle works perfectly, but doesn't when I try to use it with Kali Linux running in both VMWare and virtual box after trying so many methods, and the other laptop, I have Kali Linux installed as the main OS where also, unfortunately, the dongle isn't working, I've searched so many forums for solutions and tried every single one to no avail, any help is appreciated.
I have a Asus RT-N18U router. (but can buy another one), with DD-WRT firmware DD-WRT v3.0-r32170 std (06/01/17)
I want:
Hotspot for Restaurants that:
-People connect (no password) to WIFI
-they get a webpage (can be on router or in internet)
-webpage ask for emailadress
-once introduced emailadress and send it (to a server in internet with its MAC address) they get granted lets say 2 hours of internet
-after 2 hours they have to come back to the login page again (or better they get blocked for 10 hours with error webpage and after to login page again)
-no other service (not free and not payed) should be used

-the router mentioned offers dd-wrt with onboard radiusserver (I tried it and works), chillispot or nocatsplash (both I didn't get to work)
The router should be configured (WAN) as DHCP automatic conection and he should use his own network with his own DHCP server (so it is easy to connect him to an existing network)

I need somebody who configures the router and tell me how the configuration works. (where are modifyable files)
Hi expert

How to upload SSL to openLdap server?
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hi trying to install jboss on AWS ubunutu and access console from external/Internet

Followed so far
1. Installed Jboss on ubuntu followed these page (
2. Followed this step to allow connections from external (
3. started with -b
./ -b
./ -b <AWS Elastic IP>

when I tried to connect I get below error on the browser
This site can’t be reached.<AWS Elastic IP> refused to connect.

after I enabled TRACE. I get more info but couldn't figure out what is wrong. Please help
Pls check the attached trace.log file

thanks in advance
Dear Experts,

We have automout enabled for our /home directory, Whenever a user login to the servers automout triggers NFS mount to use to mount  home directory[/auto/home/<username>] in the servers.  The NFS servers hosted on Netapp storage device.

Below is the logs from messages file:
automount[25639]: mount(nfs): nfs: mount failure 10.x.x.x:/vol/m1_ldap_home/localhome/sivakumar on /auto/home/sivakumar
Jun  8 09:20:30 xxxxxxxxx automount[847]: attempting to mount entry /auto/home/sivakumar
Jun  8 09:20:51 xxxxxxxxx automount[25644]: >> mount: RPC: Timed out.

My Observation:

The NFS client servers which NOT in the same network where NFS Server is , having above problems.

I need to know , what angle i need to troubleshoot this issue, how to resolve and what is solution?

Thanks in advance.

We had our master DNS server go down last night for our domain (RAID failure). Technically our secondary DNS server should have picked up the slack, however for one domain where our DNS server holds the records for an externally hosted mail server of ours, it was unresponsive until we made NS2 our master server.

The biggest issue is why a secondary server would not show as responsible until becoming a master whereas other services on our network were fine...

Any ideas why this would be the case?
CentOS 7 - BIND.
I have one 12U1 SLES machine in which i want to open an port no 31015 for SAP HANA but unable to.

Netstat -tulpn also not showing LISTEN to this port .

I have also tried it with Yast2 firewall advance option but dont same problem

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0    *               LISTEN      2475/sshd
tcp        0      0  *               LISTEN      2169/master
tcp        0      0 *               LISTEN      2341/sapstartsrv
tcp        0      0 *               LISTEN      2341/sapstartsrv
tcp        0      0  *               LISTEN      2295/sapstartsrv
tcp        0      0  *               LISTEN      2295/sapstartsrv
tcp        0      0 :::22                   :::*                    LISTEN      2475/sshd
tcp        0      0 ::1:25                  :::*                    LISTEN      2169/master
udp     5376      0    *                           1308/wickedd-dhcp4

telnet IP 31015
gives keep trying then unable to reach

telnet working for other ports like ssh and 1128 etc.

please help
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redhat linux 7.3 i did disable ipv6 but still its shows.

tcp6       0      0 :::80                   :::*                    LISTEN      638/httpd
tcp6       0      0 :::22                   :::*                    LISTEN      647/sshd
tcp6       0      0 :::443                  :::*                    LISTEN      638/httpd

Linux Networking





The variety of Linux distributions creates myriad issues relating to configuration and operations when computers are networked, not the least of which is the use of various network management applications, some of which are included with specific distributions, while others are standalone applications.