Linux Networking

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Question by

HuaMin Chen

2019-09-12Solved

Folder issue in CentOS

Hi,
1. How to resolve issue below?

[code][root@28-218-217-172-on-nets home]# chown -R smb01 ~/home/share
chown: cannot access ‘/root/home/share’: No such file or directory
[root@28-218-217-172-on-nets home]#

[/code]
I want to grant write permission to user smb01.

2. Is "ls -l" enough to list out all rights of user smb01 on folder /home/share? Is there any other command?

5 Comments

I'm new to both Corosync and Pacemaker. I've looked through the documentation, and some tutorials - but I'm not sure my need is discussed. I have worked with other HA packages, so I'm familiar with most of the concepts.

In all of the tutorials, they discuss setting up a "floating IP" which is an IP address (apparently associated with a service), that is assigned automagically by Pacemaker/Corosync when the service needs to be failed over to another node.

However, in my environment, I can't use a floating IP address, specifically. ALL of the IP addresses, to ALL computers (including my servers) are assigned by DHCP based on MAC address. The MAC-to-IP association is made via a DNS adm tool (that I do have access to.)

How I have managed failover of this sort in the past is to create virtual NICs on both machines (so BOTH machines each have two VNICs, which have the same MAC addresses). Then, if I "ifconfig up" and/or "ifconfig down" the VNICs, I defacto control which server holds the IP address.

For example:

Node 1:
# ip link add link enp2s0 address 00:11:11:11:11:11 enp2s0.1 type macvlan
# ip link add link enp2s0 address 00:11:11:11:11:01 enp2s0.2 type macvlan
# ifconfig enp2s0.1 up
# ifconfig enp2s0.2 down
# dhclient -v enp2s0.1 # obtains IP 14x.xxx.xxx.001

Node 2:
# ip link add link eno1 address 00:11:11:11:11:11 eno1.1 type macvlan
# ip link add link eno1 address 00:11:11:11:11:01 eno1.2 type macvlan
# ifconfig

…

i have a centos 7 and installing httpd on it.
i open firewall for port 80 and start httpd services. service is running ok.

in my etc/hosts ihave
127.0.0.1 localhost localhost.localdomain
..
..
10.10.1.10 localhost

in my httpd.conf ihave
ServerName 10.10.1.10

browse 10.10.1.10 says : Not possible to connect to website 10.10.0.10

what is wrong here?

33 Comments

LVL 44

Question by

Rob

2019-08-11Solved

What Network Route to add (VPN)?

Hi Network Gurus,

I'm running a Linux lubuntu running PPTP VPN Server (PoPToP version 1.4.0). I can connect externally to the VPN server however I can't browse the local network, nor browse the internet.

(I know PPTP isn't secure but i'll address that another time)

What routes do I need to add to be able to browse the local network and internet when connected to VPN?

Network Gateway is 192.168.178.1

VPN Server is 192.168.178.58

VPN is setup as server 192.168.0.1 with client addresses as 192.168.1.* (i'm assuming subnet 255.255.0.0?)

Thanks for your help and please ask if you need more info

Cheers,
Rob

8 Comments

how from nginx disable url with "//"

Adding User to Ubuntu

I need a user that I can use when I do not want to risk doing damage to my Ubuntu installation.

So, I ran

sudo su

then ran

adduser curiouswebster

following these instructions,
https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-18-04

is ran
usermod -aG sudo curiouswebster

but doesn't this add root privileges for curiouswebster??

If so, please help me downgrade the permissions.

I was hoping to log in as curiouswebster and install various systems, like Apache, MySQL, PHP and WordPress.

Shouldn't I use root for this?

Also, how do I log in as curiouswebster?

Thanks

17 Comments

What excatly does
iptables -t nat -A PREROUTING -i br0 -p tcp -m tcp -d 10.0.0.2 --dport 4441 -j DNAT --to-destination 10.0.2.3:4441
mean (including the parameters)

Linux Networking

7 Comments

Question by

Dung Do

2019-06-10Solved

AutoFS Can't Mount

I am trying to mount drives using autofs. There are 3 directories that I want to mount: home, data, and web. The mount for /home works but data and web don't work. When I mounted /data and /web manually, the shares showed up. Below has the log:
Jun 10 11:09:18 testdaviddo13 automount: Starting automounter version 5.0.7-99.el7, master map auto.master
Jun 10 11:09:18 testdaviddo13 automount: using kernel protocol version 5.02
Jun 10 11:09:18 testdaviddo13 automount: lookup_nss_read_master: reading master files auto.master
Jun 10 11:09:18 testdaviddo13 automount: do_init: parse(sun): init gathered global options: (null)
Jun 10 11:09:18 testdaviddo13 automount: spawn_mount: mtab link detected, passing -n to mount
Jun 10 11:09:18 testdaviddo13 automount: spawn_umount: mtab link detected, passing -n to mount
Jun 10 11:09:18 testdaviddo13 automount: lookup_read_master: lookup(file): read entry /home
Jun 10 11:09:18 testdaviddo13 automount: lookup_read_master: lookup(file): read entry /web
Jun 10 11:09:18 testdaviddo13 automount: lookup_read_master: lookup(file): read entry /data
Jun 10 11:09:18 testdaviddo13 automount: lookup_read_master: lookup(file): read entry /misc
Jun 10 11:09:18 testdaviddo13 automount: lookup_read_master: lookup(file): read entry /-
Jun 10 11:09:18 testdaviddo13 automount: lookup_read_master: lookup(file): read entry +auto.master
Jun 10 11:09:18 testdaviddo13 automount: lookup_nss_read_master: reading master files auto.master
Jun 10 11:09:18 …

I have a scenario where I need a load balancer
When a new tcp connection is initiated from the client, the load balancer much assign a server, and always route all traffic from that that to the server it initially picked

When I netstat, I see and ipaddress and port for the client. (connection) so it makes sense to use this as the identifier for that client

Is there any software in exisitance to do this? Or do. I need to write my own?

3 Comments

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Question by

pma111

2019-05-09Solved

rpm command basics

I have executed the following command on a red hat Linux server

rpm -qa --last

to try and determine when the latest updates/patches were applied to the server. I ran this under the context of a non root account but still got some output.

A couple of questions:
--will the output of this command be full/accurate if it was executed under the context of a none root account.
---Secondly, how often are updates issued for red hat Linux, and are they cumulative / is it similar to Microsoft patch releases, and do the updates also cover security vulnerabilities. The last updates listed in the output of command were 2017 which raises some concerns that security bugs have not been patched, and therefore the server is vulnerable.
----Finally, does red hat Linux have a support lifecycle where they only continue to issue patches for certain versions, and if so where can I see where the version currently operated sits in this support lifecycle, e.g. is it still eligible for updates for new bugs/vulnerabilities.

Hello,
I am trying to install and SSL certificate on a website after i've migrated it from Ubuntu to a CentOS server.
Everything is up and running but I can't get SSL working. Apache starts fine. My config test shows no errors. But when I try to connect to the server through ssl, in all browsers I get ERR_CONNECTION_REFUSED. I don't believe its an SSL issue but maybe a firewall. I don't know as im unfamiliar with CENTOS, Any ideas?

16 Comments

I have been running Ubuntu 14 with custom tcp tuning parameters for a couple years. I applied, via puppet, all of the same tuning parameters, but on Ubuntu 18, my TCP Time Wait is very high. What is the best method of finding the source of this high TCP Time Wait? The process that is using the tcp connections is a java application.

Please let me know any other information I should provide.

Graph on the left is Ubuntu 18.04, right is Ubuntu 14.04

Thank you,

Reade
tcp-time-wait.png

3 Comments

I set up a Linux server (Ubuntu 18.10) for simple file sharing on our Windows network. The server is a Dell PowerEdge T30. It has an onboard NIC. I had given the server a static IP address and it was serving its purpose as desired for at least 2 weeks.

Last night I was testing a different (Windows) hard drive in the box, without the network cable plugged in. When I was done, I put the Ubuntu hard drive and network cable back in and rebooted the computer. When a message came up about software updates, I accepted the updates and rebooted again. When it came back up, it looked fine to me - though admittedly, I wasn't looking at it very closely.

This morning the server was not connected to the network. The network icon did not appear in the upper right corner of the screen and there was no option for the wired network in the Network control panel. When I ran lshw -C network, it said *-network DISABLED. When I entered sudo ifconfig <adapter> up, I was able to get the network connected again and join the server to the Windows domain... until I rebooted the server again, and the connection was gone again.

I also set up a separate, old Dell Optiplex 760 with the same version of Ubuntu. I do not believe I set it up to automatically update, and hadn't touched it for about a week. It too had dropped its wired network connection. My boss and I were discussing whether we should just get another network card for the server until we noticed that the other computer's network …

13 Comments

Hi everyone,

I'm searching for a tool to manage and monitor hundreds of Unix servers.
90% are on Debian but from Debian 7 to Debian 9.

I tried Cockpit and I really liked it but it is limited to 20 servers.
Webmin is not good enough.
I tried to install a CentOS server with SpaceWalk on it but I can't take the control of Debian's servers.

So I would like to know if you have some advice for me.

Tank you all.

9 Comments

I am running centos 6 and have been having issues getting a kaseya agent installed.

6 Comments

Question by

alanlam123

2019-03-07Solved

Linux

Hi expert

What is the command to check the status of the IPSec in rehat linux 7 ?

10 Comments

LVL 33

Question by

nappy_d

2019-02-05Solved

Netplan static configuration issue

I just installed Ubuntu server 18 and trying to get netplan to take my static IP but not having luck.

Can someone assist me with this?

This what I entered but it's not working.

5 Comments

I am using an older version of oxidized (rancid) to grab configs. It was build by someone else about three years ago. I'm trying to find where you configure the user ID and password to be used by the different network equipment. I don't see a reference to a user in /home/oxidized/.config/oxidized/config and not even a reference to device type PanOS which is what I'm aiming for.

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Question by

frankhelk

2019-01-24Solved

How to get tcpdump to capture continuous ?

I have some SLES 12.2 server where I need to monitor certain network traffic for diagnosing a problem that occurs every now an then. I'll try to record the traffic with tcpdump, and when that problem arises, I could dissect the correcponding network traffic with Wireshark.

I've set up a main script which contains

#!/bin/bash
tcpdump -iany -G $((30*60)) -n -w tcpdump.io.%F_%H%M%S.pcap -z ./tcpdump_postproc.sh net 192.168.1.0/24 or net 192.168.2.0/24 > tcpdump.statistics
./tcpdump_postproc.sh

and a helper script tcpdump_postproc.sh for some postprocessing:

#!/bin/bash
gzip *.pcap
find . -maxdepth 0 -mmin +$((12*60)) -name '*.pcap.gz' -delete

I'd expect that script to run indefinitely, creating capture files containing 30 minutes of data each, until I stop tcpdump with i.e. [CTRL-C] or kill. The postprocessing called after stopping (and whenever a new capture file is created) will zip the created capture files and limit the backlog of capture files to 12 hours.

So far, so good. Now to the problem:

tcpdump stops capturing data in the middle of the second file and exits (without error, as far as I could see).

What have I missed ?

8 Comments

Hi guys

We have an Linux instance in the cloud with Nginx installed on it. However, whenever the server restarts, the Nginx services don't. I'm not overly familiar with Linux commands. Can anyone help me how we can automate the Nginx services to start on restarts automatically?

Thanks for helping
Yash

7 Comments

While setting up a PXE boot server on a CentOS 7 machine, I encountered a strange problem with TFTP. I cannot retrieve any files from the TFTP server without encountering a timeout problem. The boot process comes so far that I correctly get an IP address and a file name from the DHCP server. However, when the boot files are to be retrieved from the TFTP server, a "TFTP open timeout" message comes. If I manually make a TFTP connection to the PXE server from a local computer, I immediately get access to the server. But if I try with a "get pxelinux.0" command, I get another timeout message.
My firewall is set up correctly and it also makes no difference if I completely turn off the firewall. SeLinux is also disabled.
If I make a tcpdump on port 69 I get the following message:

12:34:33.477401 IP 172.16.1.202.ah-esp-encap > tools.dmz.tuxme.dk.tftp:  27 RRQ "pxelinux.0" octet tsize 0
12:34:35.481131 IP 172.16.1.202.acp-port > tools.dmz.tuxme.dk.tftp:  27 RRQ "pxelinux.0" octet tsize 0
12:34:39.490793 IP 172.16.1.202.msync > tools.dmz.tuxme.dk.tftp:  27 RRQ "pxelinux.0" octet tsize 0
12:34:45.477712 IP 172.16.1.202.gxs-data-port > tools.dmz.tuxme.dk.tftp:  27 RRQ "pxelinux.0" octet tsize 0
12:34:53.441801 IP 172.16.1.202.vrtl-vmf-sa > tools.dmz.tuxme.dk.tftp:  27 RRQ "pxelinux.0" octet tsize 0
12:35:03.384065 IP 172.16.1.202.newlixengine > tools.dmz.tuxme.dk.tftp:  32 RRQ "pxelinux.0" octet blksize 1456
12:35:39.414843 IP 172.16.1.202.newlixconfig >