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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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Are there instructions somewhere for setting up VPN on Ubuntu via command line?

Anyone can provide any reference please?  Thank you!!
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Introduction to R
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Introduction to R

R is considered the predominant language for data scientist and statisticians. Learn how to use R for your own data science projects.

i have removed below pid file using rm command as i got some error messages with permissions on that

rm xyz.pid

is there is a way i can restore that file

I am trying to start the web logic server and having issues which used to work earlier file

Please advise
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I have just provisioned a Debian 9 VM.

My /etc/network/interfaces file reads

auto ens32

iface ens32 inet static
	address 172.16.50.210
	netmask 255.255.255.0
	broadcast 172.16.50.254
	network 172.16.50.0
	gateway 172.16.50.254

Open in new window

Yet for some reason, I end up with the system having one DHCP address and the static one I'd like for the file above.

I'm sure I am missing something obvious... but what??
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Our Solaris 10 server running Weblogic are getting thousands of messages below:
Intermittently the OS would freeze:  no core/crash dumps found.

Does this require a WL or Solaris patch or certain TCP tuning?  


Feb  5 06:17:27 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  5 12:13:03 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  6 10:28:25 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  6 11:56:35 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  7 21:57:33 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  7 22:06:34 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  8 04:24:08 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  9 21:28:25 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be under a SYN flood attack!
Feb  9 22:12:10 VGUV30 ip: [ID 995438 kern.warning] WARNING: High TCP connect timeout rate! System (port 8080) may be …
0
Previously when we transferred a 20GB gz  Solaris file down to PC's
local HDD & then from the local PC HDD, transfer to a USB HDD, our
DLP corrupted the gz file when it's transferred from local HDD to USB

We have since resolve that but to prevent untoward corruption in
future for copying of critical files to USB HDD,

Q1:
Does Winscp has checksum feature that checks at Unix end & at
PC end?

Q2:
If so I would rather use Winscp to transfer directly to USB HDD.
0
On a Redhat Linux system running a bash shell script I need some help with an if then statement that has more than 2 conditions. I basically want to check for this
A AND B or C  
A AND B or D
A AND B or E

Something along these lines but it doesn't work and wondered if I have the correct usage of brackets. It's not what's contained for evaluation that's the issue it's the syntax of the AND and OR where there's more than two conditions that I am struggling with.

if [[ $(find /opt/app -name httptd*.conf | grep -v grep | grep -c http) -eq 0 ] && [ ! -f /etc/init.d/apache ] ||  [ $(find /app -name http*.conf | grep -v grep | grep -c http) -eq 0 ]] || \
[[ $(find /opt/app -name httptd*.conf | grep -v grep | grep -c http) -eq 0 ] && [ ! -f /etc/init.d/apache ] ||  [ $(find /application -name http*.conf | grep -v grep | grep -c http) -eq 0 ]] || \
[[ $(find /opt/app -name httptd*.conf | grep -v grep | grep -c http) -eq 0 ] && [ ! -f /etc/init.d/apache ] ||  [ $(find /application -name manifest* | grep -v grep | grep -c http) -eq 0 ]] ; then
.....
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Dear Experts

We are running web server (10.253.18.41) which is on lamp stack and database server mysql is on another server 10.253.12.42, users are complaining the application is taking too long time also on prospect conversion takes too much time and finally timeout approx 3 mins then time out , when check the network statics below is the continuous report, please let me know what does this indicate, what could be the solution

tcp        0      0 10.253.18.41:38760          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38765          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38274          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38130          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38590          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38116          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:39296          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38577          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38379          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:39027          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38827          10.253.12.42:3306           TIME_WAIT
tcp        0      0 10.253.18.41:38222          10.253.12.42:3306           TIME_WAIT
tcp        0     …
0
Dear Experts

CRM system work flow triggers emails to the prospect email account as and when the prospect statues changes via the SMTP server ( without password that is without authentication as it is Relay server hosted locally-office 365 mail protection ). We could see the connection to the email server getting established but no packets sent/received , but through telnet we can send and receive mails by making use of from and to email commands through the telnet session, can you help where the things are going wrong. following SL2 cases it works but SL3 it does not work.
1. though telnet to the smtp server with FROM and TO commands it works that is mail is delivered to the TO addressed account.
2. though CRM system configure email settings with email account, smtp and port without the SMTP authentication mail is getting delivered to the To account.
3. CRM system through workflow trigger email on each status changes mail is not getting delivered instead we can see connection is ESTABLISHED to the smtp server
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For this question, let's forget about v-nodes/vnodes. So let's say the contents of a file are located in data block(s) on a real physical disc.

See for example: https://www.usna.edu/Users/cs/aviv/classes/ic221/s16/lec/21/lec.html#orgheadline4

2.3 V-node and I-node Tables

There they explain the inode-table. Actually the inode-table just leads you to the contents of a file. But I think they forgot to mention something important. Let's say I'm requesting a regular file in a filesystem. In such a case, for what I need the inode-table? I just see it like this:

dentry (possibly more than 1) -> inode -> data block(s)

The inode contains the pointers to the data block(s). So why we need an inode-table? Or is this inode from above actually just an entry in the inode-table? If that's true, then it's weird because the inode-table is stored in memory, so when restarting the computer all the inodes are gone. Furthermore, probably the inode-table only contains information about open files.

Or are the inodes of open files just cached in memory (in the inode-table) to speed things up? Then the purpose of the inode-table is i.a. caching?

Anyway I'm surprised that they don't say anything about this. I think understanding the inode-table starts with the question why there is an inode-table.
0
Dear Experts

In windows server where the application server (CRM system)  is deployed this application which connects to multiple integrations like website , CTI, also configured office 365 smtp, the application logs are not giving us enough data hence from the windows server level how to find or get the log report , when the CRM application runs logic based on scheduler it triggers emails to the customers to check this from windows server level what to do please suggest, in linux think we can use netstat - tulnp, In windows server how to find the application which is running is it establishing connection to the remote services like smtp configured. for example
1.  would like to run the command where it lists  only the running smtp connections established
2. would like to run the command where it lists all the connections established to web server.
also is it possible to append to text file
0
Python 3 Fundamentals
LVL 12
Python 3 Fundamentals

This course will teach participants about installing and configuring Python, syntax, importing, statements, types, strings, booleans, files, lists, tuples, comprehensions, functions, and classes.

Does anyone know How can I see the interface up and down logs in the ubuntu 18.4? there should be something like /var/log/dmesg shows logs
0
Dear Experts

We are having web-based application on linux which uses LAMP  which is production server recently the web-based application stops working for some time later it resumes back and when checked the /var/log/messages can find the following
kernel: Out of memory: Kill process 249606 (httpd) score 32 or sacrifice child
Sep 13 13:19:27 NYSWB kernel: Killed process 249606, UID 48, (httpd) total-vm:2826972kB, anon-rss:1334424kB, file-rss:2044kB
attached /cat/proc/meminfo and also fdisk -l , the system has 32G of physical RAM,
please suggest should i have to create one more swap partition OR should I have to edit swap config if yes please help me with steps, or any other steps on any config to be done please let me know, thank you.
memandfdisk.txt
0
Dear Experts

application server web-based of LAMP stack becomes extremely slow and makes application unable to use, web-server(application file system) is having 16GB Ram and database server is separate with 64GB ram and did run mysql tuner attached for your reference below posted recommendation section, when try to set values as recommended mysql fails to start  withe following error log, please help on what values to set so that below error is fixed, thank youmysqltuner12.txt
Plugin 'InnoDB' init function returned error.
180911 14:18:19 Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
180911 14:18:19 Unknown/unsupported storage engine: InnoDB
180911 14:18:19 Aborting

Below -extract of recommendations section from the attached

-- Recommendations ---------------------------------------------------------------------------
General recommendations:
    Control warning line(s) into /var/log/mysqld.log file
    Control error line(s) into /var/log/mysqld.log file
    Set up a Password for user with the following SQL statement ( SET PASSWORD FOR 'user'@'SpecificDNSorIp' = PASSWORD('secure_password'); )
    Restrict Host for user@% to user@SpecificDNSorIp
    MySQL was started within the last 24 hours - recommendations may be inaccurate
    Reduce your overall MySQL memory footprint for system stability
    Dedicate this server to your database for highest performance.
    Adjust your join queries to always utilize …
0
I am sysadmin..I want to know

I want to reach the server, to check the connectivity thru specific port.
This is just to varify whether the required firewall rule defined properly or not.
0
Consider the below scenario

userPC---- firewall --- Destination-server
                         10.1.1.1


I have installed some software on the server, the service  of that software is using port # 301.

1) Scenario...
      Firewall defined
      server#  service UP
        userPC# telnet 10.1.1.1 301  --> user get reply

2)Scenario...
      Firewall defined
      server# service DOWN

is there any command/3rdparty-tools available to just varify, pockets from userPC able to reach on the server through port#301

==
This I asked just to segregate if there any issue, problem from firewall side (or) destination server side.
0
Dear Experts

in linux server of centos,  we are running crm which is web based application apache, mysql and php once in few hours users are getting timeout and this is affecting very badly,
1. would like to fetch the log reports of server resources consumption like  RAM, CPU to understand the issue is occurring due to over load of that particular time.
2.  would like to fetch apache logs and mysql logs of that particular time
to determine the time that users are facing issues of application time out , Can I ask software developer to provide me time out occurred and application closed  date and time and during that time check the server resource utilisation which will help me to trace the issue is it due to server or application level.
please help on best practice on such cases.
0
rsync error on ubuntu 16.04 server.
i try to sync folder between two ubuntu server and say
sshpass -p password@ rsync  ssh -avhre user@ip_server:/home/my/direct/ /home/my/
rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1655) [generator=3.1.1]

Help!!!
0
Hi ..CCan anyone tell me what is this service "icl-twobase1" running on port 25000 ?
0
Hello Experts,
I am trying to change the mail behavior of fail2ban to /etc/fail2ban/jail.local section mta=.
I would like to generate a fail2ban mail filter that uses swaks as mail client although the authentication, mail from, mail to are already pre-set. Unfortunately I don't find any meaningful examples in my internet search and wanted to ask politely if someone has such a configuration already running. Thank you so much

With kind regards reredok
0
Learn SQL Server Core 2016
LVL 12
Learn SQL Server Core 2016

This course will introduce you to SQL Server Core 2016, as well as teach you about SSMS, data tools, installation, server configuration, using Management Studio, and writing and executing queries.

I want to create a server(OS: CentOS) which will be acting as an interface to an Android app(client) and the database.

I am not much experienced in programming and I just want a little bit of guidance right now to get started.
I have decided that I want to program the server in C++(though it's not an easy language but I believe there's much more to learn while programming in C++)

The basic functionality I want from my server:
1. It will interact with the app via https.
2. The server and client(app) will communicate via REST APIs.

I want guidance in terms of the most stable and well documented external C++ libraries that I should use to program the above server(I've looked at zmq, libcurl, netlib-cpp but due to my lack of experience I don't even know if these are really related to my problem statement). Thanks in advance. Please feel free to attach any blog/article/video which might be relevant.
0
I have multiple NICs on my Redhat 6 x86_64 server and as part of my script I have to determine which NIC is the default gateway on each server since there are lots of static routes over the other NICS. I always see the default gateway as the last line in the routing table but is that logic flawed and I just run net stat -rn | tail -1 | awk '{print $8}' but I'm not sure if that logic is up to par and I'm going to have to tally it up with what's in /etc/sysconfig/network as the gateway.
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I recently cleaned my server off, and installed a fresh copy of centos 7 linuxs on it. My issue is i have ssh running, but i am only able to access it with my private ips. I am not clear on how to set it up to use my static ip and domain names? Please help? The domains are not setup yet, since i just installed centos 7 again. i need help with the basic understand of setting my ssh up to allow remote access in another city.  when i try to use my static ip to access it i get this error "port 22: No route to host ". My firewall is complete down, so there or not blocks, so it has to be a configuration issue. i Just dont know what to do to fix it.
0
Dear All

  I have a centos 7 acting a router, and found out using a speed test the upload speed is very slow, whereas the download speed is reaching 99mbps, I try to by pass the centos and direct connect to a laptop , the upload speed show 99mbps, any idea what limited the upload speed on centos ?


Keith
0
I installed dietpi today on a Zero w. (did it on a 3B+ and setup as Hotspot no problem). I wanted to setup the zero as a webcam.
I did this 4 times before I started to install or change the configuration and reboot at least 2 times to make sure all was good.
I changed the setup to US. connected to the Wi-Fi.
Updated to the latest version of dietpi. Update the firmware.
Changed drop bear to ssh.
installed REALVNC.
But when I Install RPI WEB CAM it keeps rebooting and I can't stop it.
As I said after the 3rd time I flashed a fresh image again and rebooted at least 2 times after each change or install until I got to the RPI Web CAM issue.
I get "You're in emergency mode. Enter root password for maintenance or CTRL D.
I tried dietpi for the password and root. CTRL D does nothing but reboot back to the same area.
I'm assuming there is am issue with RPI Web Cam.
And Yes I made sure the power supply is good. I replaced the power supply with one used on my Pi3B+. It's 5.2V, 3amps.
I even tested it with my voltmeter. The issue is this pi Zero W setup works fine with a full version of Raspian and the RPI WEB CAM version I had to manually configure. I switched back to that card and all is fine. I just like the small footprint and ease of setup with DietPi. And it only starts to reboot when I add in the Web Cam distro on DietPi. I even tried some other packages after my 4th attempt, on the card, flashed a new image. In fact I added a few distros to the DietPi setup …
0
Dear Experts

in the Windows Active Directory domain controller environment joining the windows client to the domain controller by assigning the IP address and preferred DNS pointing to Windows AD server (which functions as domain controller and also name server).
 Joining the windows client does not require manually creating the entries in the forward and reverse zones, the moment windows client device is joined the records are automatically created in the DNS server.   Now how to make Linux servers in the network to use windows AD server as its  DNS server,  should we have to manually create forward zone and reverse zone entries and then configure Linux server to use windows AD server as its DNS server, please suggest .
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.

Top Experts In
Linux Networking
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