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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i am in particular folder say abc.

I did ls -ltr where there are bunch of files.

i want to search all the files starting with file name xyz alone ignoring other starting with pqr etc(ignore pqr000.log.20170806.gz etc).
My search should result like

xyz789.log.20170806.gz etc

What is the command i have to use for that.

is it grep or find or something else.

when i gave grep xyz.* it did not gave any result.

how searching inside a file content is different from search outside on unix file names.

any good link on these commands? please advise
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thanks !

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?
Hi experts

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

OS - CentOS 7

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
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!!
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A new era in Cloud training has arrived.

A day that will go down in Cloud history.. But are you ready for it? Will you accept this Cloud challenge?

Hi expert

How to upload SSL to openLdap server?
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.

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
How can I configure BIND DNS to work as a slave for Windows DNS for different environments.  I already built and configured for DNS Bind to work as a slave in a LAB environment however Im trying to phase this into other environments at a slow pace. I created a template and using puppet to configure the environments.  I put an if statement in there for LAB, would it be a else or elsif for another environment or am I going about the wrong way?  Any help would be appreciated.  Thanks!

Template code
#Global Options
options {
  directory "/var/named";
  listen-on port 53 { localhost; <%= @ipaddress_eth0 %>; };
  allow-query { any; };
  dump-file   "/var/named/data/cache_dump.db";
  statistics-file "/var/named/data/named_stats.txt";
  memstatistics-file "/var/named/data/named_mem_stats.txt";
  recursion yes;
  empty-zones-enable no;
  check-names master warn;     #Must be WARN only for AD
  dnssec-enable no;
  dnssec-validation no;
  dnssec-lookaside auto;

  ## Path to ISC DLV key ##
  bindkeys-file "/etc/named.key";

  pid-file "/run/named/";
  session-keyfile "/run/named/ses.key";

#Logging Section  -- What, how, and where logging takes place can be extensively configured in BIND
logging {
  channel default_file {
      file "/var/log/named/default.log" versions 3 size 5m;
      severity dynamic;
      print-time yes;
  channel general_file {
      file "/var/log/named/general.log" versions 3 size 5m;
      severity dynamic;
      print-time yes;

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when i start the tomcat service i get this error.

server[3387]: May 29, 2017 2:33:36 PM org.apache.coyote.ajp.AjpMessage processHeader
server[3387]: SEVERE: Invalid message received with signature 18245
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0*               LISTEN      1/systemd
tcp        0      0  *               LISTEN      5308/mongod
tcp        0      0   *               LISTEN      652/sshd
tcp        0      0 localhost:smtp*               LISTEN      907/master
tcp        0      0 localhost:32000*               LISTEN      2418/java
tcp        0      0 localhost:27017*               LISTEN      1797/mongod
tcp6       0      0 [::]:monkeycom          [::]:*                  LISTEN      2418/java
tcp6       0      0 [::]:sunrpc             [::]:*                  LISTEN      1/systemd
tcp6       0      0 [::]:webcache           [::]:*                  LISTEN      3387/java
tcp6       0      0 [::]:http               [::]:*                  LISTEN      4534/httpd
tcp6       0      0 [::]:ssh                [::]:*                  LISTEN      652/sshd
tcp6       0      0 [::]:ddi-tcp-1          [::]:*                  LISTEN      28290/node
tcp6       0      0 localhost:smtp          [::]:*                  LISTEN      907/master
tcp6       0      0 [::]:https              [::]:*                  LISTEN      4534/httpd
tcp6       0      0 localhost:mxi           [::]:*                  LISTEN   …
[root@web02 ~]# cat /etc/*-release
CentOS release 6.8 (Final)
CentOS release 6.8 (Final)
CentOS release 6.8 (Final)

[root@web02 ~]# yum info -v apache-tomcat-apis
Loading "fastestmirror" plugin
Config time: 0.076
Yum Version: 3.2.29
rpmdb time: 0.000
Setting up Package Sacks
Loading mirror speeds from cached hostfile
 * base:
 * extras:
 * updates:
pkgsack time: 0.126
Installed Packages
Name        : apache-tomcat-apis
Arch        : noarch
Version     : 0.1
Release     : 1.el6
Size        : 246 k
Repo        : installed
From repo   : base
Committer   : Andrew Overholt <>
Committime  : Tue Feb  2 07:00:00 2010
Buildtime   : Wed Nov 10 19:18:17 2010
Install time: Sun May 28 11:58:23 2017
Installed by: root <root>
Changed by  : System <unset>
Summary     : Tomcat Servlet and JSP APIs
URL         :
License     : ASL 2.0
Description : Apache Tomcat's Servlet 2.4/JSP 2.0 and Servlet 2.5/JSP 2.1 APIs.

[root@web01 ~]# cat /etc/redhat-release
CentOS Linux release 7.3.1611 (Core)

[root@web01 ~]# yum info -v apache-tomcat-apis
Loading "fastestmirror" plugin
Config time: 0.009
Yum version: 3.4.3
rpmdb time: 0.000
Setting up Package Sacks
Loading mirror speeds from cached hostfile
 * base:
 * extras:
in Unix

what is the meaning of below command

zgrep 'RPT|O|GetProducts' xyz.gz meaning
why we need RPT|o|
in the beginning what is the meaining of pipe here?
please advise
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Imagine the following scenario:

A NAS box, providing a samba share, with several versions of a fíle collection in dated directories (name i.e. "2017.05.24").

On the NAS should be some links into subdirectories of the latest version, so the copy script should create symbolic links on the share to the latest version of that file collection.

When I try
ln -s <samba_share/link_name> <samba_share/dated_dir_subdir/>

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I get an error that this is not possible. Any hint ?
Can anyone recommend a good Linux tutorial, learning from the ground up?
Hi experts
I have mikrotik router board v5
Using hotspot
I need antivirus rule for my system

what are the best practices and features, options while using grep.

i am using these days to search in log files, files, directories, content etc

When should i give single quote '  '
zgrep 'xyz' aaa.gz

When should i give double quote " "
zgrep "xyz" aaa.gz

how to use tail and head etc along with grep to effectively monitor last or first 100 lines etc
please advise

I keep getting below error when i wrote shell script file and try to open it to.

Swap file "" already exists!
[O]pen Read-Only, (E)dit anyway, (R)ecover, (Q)uit, (A)bort:

why it created .swp file autoatically?
why it asks above question. How to tell unix not to ask that question.
please advise

I created script using vi
then typed below

echo "Hello, World!"
echo "Knowledge is power."

do i need to tyope below line as well at top?

what above line means?

when i try to execute gets errror as

$ ./
-bash: ./ Permission denied

please advise

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.

Top Experts In
Linux Networking