Linux Networking

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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 have recently installed an Ubuntu 16.04 VHD image. Initially the /etc/network/interface file was empty. I put in the ip address info that I was provided by our network guy.
ifconfig showed eth0 as the interface name.
I edited the interface file to have the following:
auto eth0
iface eth0 inet static
address 10.100.1.6
gateway 10.100.0.1
submask 255.255.248.0
dns-nameservers .....

the network folks changed their minds and wanted to put my server on a different subnet.
I have edited the interface file.
auto eth0
iface eth0 inet static
address 10.99.0.6
gateway 10.99.0.1
submask 255.255.240.0
I have flushed the interface.
I have tried rebooting and actually shutting down the system.

but each time when I boot back up the interface continues to be configured with the old IP.

what am I doing wrong?
What do I need to do in order for the new IP to be loaded into the configuration?

Thanks in advance.
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what is the meaning of below command

less log123.log | grep -i nullpointerexception


why we use less and then grep on it

Please advise
0
in vi we can use /nullpointerexception to find that string right.

how to find how many occurrence of that string total and go to say 10th occurence line
please advise
0
when i open with winscp that opens old stale file compared to putty opening of same file say xyz.ccfg

i wonder why winscp does not show recent changs?

please advise
0
tail -f logfile.log


what is the meaning of above command.

i see logs rolling too fast.

is there is a way i can slow it down to see clearly slowly

any god tips, links, resources on how to debug production logs efficiently just using putty without any fancy costly tools?

please advise
0
Dear Experts

Have installed ubuntu desktop 16.4  and created a users  are put into  standard group (non administrator) how do I restrict this standard user not to use wifi and bluetooth services. I want the users limited  wired connection . I mean should not be able to select the wifi also should not be able to use bluetooth please suggest, I would like configure this please suggest. thanks in advance.
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My goal is to be able to connect to private network located behind OpenVPN client (192.168.1.0/24) via OpenVPN server WAN interface.
For example I want this forwarding: http://{Ubuntu WAN IP}:443 -->  http://{Private LAN IP behind OpenVPN client }:443
Please take a look at the attached screenshot.
-  Ubuntu VPS knows the route to private LAN subnet that is behind OpenVPN client (192.168.1.0/24) and MikroTik router knows the route to OpenVPN subnet (192.168.7.0/24).
- I can connect to Ubuntu VPS via SSH and successfully ping MicroTik OpenVPN interface (192.168.7.2) and also I can ping any host from MicroTik private LAN subnet that is behind OpenVPN client (192.168.1.0/24) , needless to say the private LAN hosts that are behind OpenVPN client (from 192.168.1.0/24 subnet) can easily ping Ubuntu OpenVPN interface (192.168.7.1) too.
- Also any host from OpenVPN subnet (192.168.7.0/24) if connected to OpenVPN server via OpenVPN client allows communication like http://{Ubuntu WAN IP}:443 --> http://{Private IP of OpenVPN client}:443 using UFW NAT rule.
But:
When I’m trying http://{Ubuntu WAN IP}:443 --> http://{Private LAN IP behind OpenVPN client}:443 I have following behavior:
1)      Packets successfully arrive to host behind OpenVPN client (to any host from 192.168.1.0/24 )
2)      But the host of this subnet can't route back this received public IP packet via OpenVPN tunnel, it replies using ISP WAN address.

I would very happy if someone is able to help me solve this …
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no one in ubuntu 16.04 can change password. permission deni...
and new user (sudo adduser (not permission to give a password).
0
Hello Community,

I need some help installing Opennms monitoring software because Im getting error trying to install it on Oracle Linux 6.9.

I used this commands:

wget https://yum.postgresql.org/9.3/redhat/rhel-6.9-x86_64/pgdg-oraclelinux93-9.3-3.noarch.rpm

Open in new window

yum install postgresql93-server postgresql93-contrib uuid-pgsql.x86_64 repmgr93.x86_64 rhdb-utils.x86_64 skytools-93-modules.x86_64 pgbackrest.x86_64 pgdg-oraclelinux93.noarch pgloader.x86_64 pgmemcache-93.x86_64 pgmp93.x86_64 phpPgAdmin.noarch pgagent_93.x86_64 ora2pg.noarch -y 

Open in new window


Then, with sudo rights did:

sudo bash bootstrap-yum.sh

And getting the error below:

PostgreSQL initialize                 ... FAILED

Open in new window


Im using the installer provided by official site.

Regards,
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how to import sessions from putty or mputty to securecrt.
https://www.vandyke.com/products/securecrt/

I recently installed securecrt not sure how to import all existing conections to different servers on different environments that are present in putty to winscp.

any tips on effective use of securecrt as i am new to it

Please advise
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Dear experts,

I am new to the DNS and DNS load test. Now i have task to test Load Test on two BIND9 servers [RHEL6]. I had googled it and i found dnspref is good tool to evaluate throughput and latency. However, I need a script to do this task. I will be very helpful for me if any one share the info.

thanks,
Maddy..
0
hi am geting this error when starting my linux
linux
0
Hey all, I am struggling with trying to get this to work, I really hope someone can spot what the issue is.

I have a working OpenVPN server running that has many clients connected to it. These clients are able to communicate with any devices on the OpenVPN 10.100.101.0 network. I set up a Sierra Wireless RV50 with an OpenVPN client with static ipp.txt entry of 10.100.101.17. I have set up iroutes in client ccd files and set a route on the server and I am now able to ping both subnets 192.168.13.0 and 10.100.101.0 from each other. However, I only want the OpenVPN subnet 10.100.101.0 to communicate with devices on the 192.168.13.0 network but not have the 192.168.13.0 network be able to talk to any device on the 10.100.101.0 network besides the server, 10.100.101.1. Hopefully that makes sense.

I figured this has to go in the FORWARD rules, but what I've entered is not working. Can anyone help? Thanks in advance.

Here is the output of my rules but I am still able to ping everything across both subnets.

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination        
    0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ftp
    6   436 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh
    0     0 ACCEPT     udp  --  any    any     anywhere             anywhere             udp dpt:domain
    0     0 ACCEPT    …
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I have an OpenVPN server which is configured as per this article: https://www.digitalocean.com/community/tutorials/how-to-set-up-an-openvpn-server-on-ubuntu-16-04

When I connect to the VPN server using native OpenVPN IOS app I get ~18Mbps down, ~3Mbps up on Speedtest.net IOS app

When I connect to the VPN using Windows 10 (using official OpenVPN client) I get ~18Mbps down, ~3Mbps up on Speedtest.net

I'm happy with those speeds.

What I'm trying to do is have a wireless Access Point called 'VPN-AP' and have it so whenever a device (iPhone, AppleTV, laptop etc.) connects to this, their internet traffic is routed down the VPN.  

I've successfully achieved this, in turn, on each of the following devices, but I can never get half-decent throughput for the clients.


  • RaspberryPi 3, using Hostapd, dhcpd and OpenVPN
  • Linksys E2500, flashed using Tomato (using Tomato's built in OpenVPN client)
  • Windows 10 using official OpenVPN client and shared using a hostednetwork and Internet Connection Sharing

Whichever of the above I use, the performance for of the client connected to the hosted WiFi is TERRIBLE in comparison to the speeds posted above.  At best 5Mbps down, 1Mbps up (Windows 10 with ICS).

None of the 'proxying' devices are straining their CPU and neither is the OpenVPN Server to which they all connect.

For clarity, I can sit on the Win10 PC with the OpenVPN client connected, open SpeedTest.net …
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1. Can someone explain me if there is any changes in .cloginrc file, I need to run the rancid-cvs and rancid-run,
2. When i am trying to login i can see that the username is not pulling from what is there in .cloginrc.

For Eg:
(Under my clogin file)
I have mentioned
add user 1x.x.x User1
add password 1x.x.x       {password}
add method 1x.x.x telnet ssh

But when i am trying to login, i can see that username is in rancid. I am not sure why its happening. And to make sure that if try firewall login or normal login, its going with actual username only
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on my windows 10 machine after installing oracle virtua box and centos on top of it while starting getting below error


Failed to open a session for the virtual machine centos.

The virtual machine 'centos' has terminated unexpectedly during startup with exit code 1 (0x1).  More details may be available in 'C:\Users\saiganesh\VirtualBox VMs\centos\Logs\VBoxHardening.log'.

Result Code: E_FAIL (0x80004005)
Component: MachineWrap
Interface: IMachine {b2547866-a0a1-4391-8b86-6952d82efaa0}

i tried on other laptop i do not see red hat 64 some reason but shows red hat 32 bit

Please advise
centos.png
centos.png
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how to remember shell history and how to save unix queries for future use and share with the team

$HISTSIZE can be increased to unlimited size?

how to type attached l character

please advise
L_char.png
0
how below commands are different

su department (when i do pwd here says department)
vs
su - department(when i do pwd here says /home/department)

when i do below

su -c 'echo $echo  $DEPARTMENT_HOME' department
it does not work

when i do below

su -c 'echo $echo  $DEPARTMENT_HOME'  - department
it does work. Please advise the difference.

what is difference between
department and  /home/department

how su and sudo are different?

how can there is depearment inside home as well as outside at top level again?

what is visudo and sudoers file or folder?

Please advise
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difference between below process killing signals

kill -15 123

vs

kill -TERM 123
vs

kill -9 123


how foreground and background processes are different and how to kill or suspend them?
is PID is always 4 digit or it can be 10 digit etc?

how job and process different?
how to distinguish between background and foreground jobs?

when i say
jobs

it simply shows 5 different jobs one with + other with -

but does not show whether background or foreground?

i have a job running in background i brought it to foreground and stopped it.
when i moved it again to background it automatically moved to RUNNING status? how this is possible?
how terminated suspended and killed etc are different?
Please advise
0
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Cloud Class® Course: Microsoft Office 2010

This course will introduce you to the interfaces and features of Microsoft Office 2010 Word, Excel, PowerPoint, Outlook, and Access. You will learn about the features that are shared between all products in the Office suite, as well as the new features that are product specific.

ubuntu 16.04 ask always to times for password. How to disable that?
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PPTP VPN on Linux Mint won't connect to Windows Server 2016 server. Windows 10 will connect PPTP both externally and internally. Linux fails with an error saying "VPN disconnected because the VPN service stopped"
Server 2016 VPN is set to use MSCHAPv2 only.
WIndows 10 connects when set to use MSCHAPv2 only.
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I am trying to access tomcat and i don't see any page shows up

http://192.168.2.18:8080

i also did check the firewall and i did rule the firewall issue.

Redhat 7

[root@web01 ~]# netstat -pant
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:8009            0.0.0.0:*               LISTEN      1614/java
tcp        0      0 192.168.2.18:8080       0.0.0.0:*               LISTEN      1614/java
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      938/sshd
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      1197/master
tcp        0      0 127.0.0.1:8005          0.0.0.0:*               LISTEN      1614/java
tcp        0      0 127.0.0.1:8009          127.0.0.1:33358         TIME_WAIT   -
tcp        0     64 192.168.2.18:22         192.168.2.10:62364      ESTABLISHED 1297/sshd: root@pts
tcp        0      0 127.0.0.1:8080          127.0.0.1:59988         TIME_WAIT   -
tcp        0      0 192.168.2.18:22         192.168.2.10:62356      ESTABLISHED 1251/sshd: root@not
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Is it possible to creat two domain in samba aktive directory on ubuntu. One for .local and other one for .com .
What  shouls i know to do this? Is there any documentation to do this?
0
securecrt vs putty

what additional feature or advantages or disadvantages securecrt has compared to putty or mputty.

how much is the licence cost per year or life time?

any advantages using securecrt or any other commercial better tools?

please advise
0
Hello Experts,

I'm having some problems with firewall rules and would like the help of you guys.

I added a VPN connection (StrongSwan), but I can not access the network from the other end.

when I run the firewall script (iptables), the script flushes the rules (filter and nat) and adds the new rules. While the script rules are not added (policy: accept) I can access the other end of the VPN, but when the nat table rules are added, I lose the communication.

Yes, I know there must be an error in the nat rules, but I can not figure out exactly which rule(s) is(are) causing that impact.

I tried to use iptables TRACE, but I have a lot of rules applied and I can not understand the results and I can not locate exactly what the problem is.

And now the weirdest part (I think): I have another VPN connection (another network destination) configured on the same machine, with exactly the same rules and do not have this problem.

Can any of the experts give me an idea of how I can try do the troubleshooting or know how I can try to solve this problem? I'm lost!

Thanks in advance!

Best Regards
0

Linux Networking

18K

Solutions

15K

Contributors

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.