How to configure OpenDKIM on Linux with Postfix and setup bind zonefile

This guide assumes you have a working Postfix server and want it to sign with DKIM. There are a few things we have to understand to make all of this work though, which require you to be familiar with DNS as well. 1.) Install OpenDKIM apt install opendkim systemctl enable opendkim 2.) Edit /etc/opendkim.conf Syslog yes SyslogSuccess yes Mode&nbs........

isc-dhcp-server dhcpd how to get longer lease

You can do a static lease that is tied to the MAC address but what a lot of users prefer is that they come into the office or lab the next day and that their device gets assigned the same IP address (if possible). As we can see in the dhcpd logs that there is threshold that is defaulted as we'll show later. Whatever the threshold is set at, if the lease is younger than the threshold, it will keep the same lease. In other words, if the device goes to sleep or is powered off........

nvidia cannot resume from sleep Comm: nvidia-sleep.sh Tainted: Linux Ubuntu Mint Debian

This seems to happen in many different drivers but it happened more often in newer versions such as 530 vs 525. Then nvidia-modeset goes to 100% There are many reports of this appearing since driver 4.70 and I can confirm I've seen this in various machines. https://forums.de........

zfs and LUKS how to recover in Linux

Sometimes users take their removal drives and unplug and replug them to test what happens during the failure of a disk. However, this breaks things quite badly due to the /dev/mapper in LUKS not coming back online due to it not being closed. In other words, generally with non-encrypted drives the process is smooth but when encrypted you may want to follow a strategy like this: We can see below that both disks are unavailable as they were physically remov........

Postfix / sendmail config for DKIM, SPF and DMARC Tutorial Guide E-mail Delivery for Hotmail.com Gmail.com and More HowTo

This will be the goto to help solve e-mail delivery issues and talk about many practical issues that happen between developers, admins and scripts that send e-mail and do things that may not be acceptable or cause deliverability problems. Sendmail Stuff Edit /etc/mail/sendmail.mc The problem is that if you send directly out from the server using the mail function, the Return-path of the e-mails will be username@thehostnameoftheserver.com. Let........

How To Upgrade Debian 8,9,10 to Debian 12 Bookworm

Step 1.) Upgrade to Debian 11 first The process to go to Debian 12 is not as smooth as 11, when trying to upgrade from Debian 10. In fact, it doesn't work directly, so you'll first need to follow this guide to update to Debian 11, reboot and come back here if successful. Step 2.) Update sources.list Update your /etc/apt/sources.list like this: deb http://........

Linux dhcp dhclient Mint Redhat Ubuntu Debian How To Use Local Domain DNS Server Instead of ISPs

If you are running a local DNS server like named/bind and don't want to use the ISPsupplied DNS servers that are announced via a DHCP request (using dhclient) then the solution is simple. The reason should be obvious, but normally running your own DNS server will provide a more reliable, and fast DNS response and you won't have to worry about filtering as much (unless your upstream filters or proxies outgoing DNS requests). Edit /etc/dhcp/dhclient.conf........

Linux Ubuntu Mint how to check nameservers when /etc/resolv.conf disabled solution

You'll notice that /etc/resolv.conf contains dire warners on most Linux Desktops. # This file is managed by man:systemd-resolved(8). Do not edit. # # This is a dynamic resolv.conf file for connecting local clients to the # internal DNS stub resolver of systemd-resolved. This file lists all # configured search domains. # # Run "resolvectl status" to see details about the uplink DNS servers # currently in use........

How To Add Multiple SSH Keys Ubuntu Mint Linux Debian Redhat

By default if you create a private key for SSH, it will create something like .ssh/id_rsa Linux will always search for and offer this key when connecting to servers. If you put extra keys in your .ssh directory like id_rsa_realtechtalk.com, they will be ignored by default and NOT used or offered (you can verify this with ssh -v) and see it is not being offered. Here is how you add the extra SSH keys so they are all offered: #this gives........

iptables NAT how to enable PPTP in newer Debian/Ubuntu/Mint Kernels Linux

Remember that control connections are established on port 1723 and then actual data is transferred over GRE protocol 47. If you have a NAT setup this will work without special forwarding or accepting of GRE packets (normally if you are not blocking outgoing connections and accepting established and related connections). The below two commands will get things going so PPTP and GRE work We first load the ip_nat_pptp module which allows PPTP to work with........

Linux How to Check Which NIC is Onboard eth0 or eth1 Ubuntu Centos Debian Mint

So say you happen to have 2 NICs of the exact same chipset, they will generally show up as the same name, with possibly a different revision in lspci. Normally this is not an issue if you have a server with 4 NICs, generally the eth0 to eth3 appears from left to the right (or right to left on some vendors) so it doesn't take much figuring out. Generally if you have different chipsets for different NICs, it should be easy to know which one is eth0 or the first NIC in the OS.........

Cisco Switch / Router How To Restore Factory Default Settings

1.) Make sure your conf register is 0x2102 Do show version and at the very end of the output you will see the Configuration register. show version Configuration register is 0x2102 If the config register is not 0x2102 then enter this command: r1#configure terminal r1(config)#config-register 0x2102 r1(config)#end 2.) Let's Erase the NVRAM/flash........

RTL8821AU Setup Configure Wifi Realtek 8821 in Linux Debian Mint Ubuntu Howto

The easiest way for the 8821AU Realtek Wifi chipset / TP-Link T2U Plus: Bus 002 Device 003: ID 2357:0120 TP-Link Archer T2U PLUS [RTL8821AU] First install your kernel headers/source/other required tools: sudo apt install linux-headers-`uname -r` make gcc bc Clone this github repo with the driver: git clone https://github.com/morrownr/8821au-20210708 Run the compile/ins........

How To Do Linux Network Bonding Teaming in Mint Debian Ubuntu

Bonding is an excellent way to get both increased redundancy and throughput. It is similar to the "Network Teaming" feature in Windows. There are a few different modes but we will use mode 6, I think it's the best of both worlds, as it is not just a failover, but it provides round robin, so you will get redundancy and load balancing. So if you have a 1G single port, you will have a combined throughput of 4G at this point. Just bear in mind that the true thr........

GlusterFS HowTo Tutorial For Distributed Storage in Docker, Kubernetes, LXC, KVM, Proxmox

This can be used on almost anything, since Gluster is a userspace tool, based on FUSE. This means that all Gluster appears as to any application is just a directory. Applications don't need specific support for Gluster, so long as you can tell the application to use a certain directory for storage. One application can be for redundant and scaled storage, including for within Docker and Kubernetes, LXC, Proxmox, OpenStack, etc or just your image/web/video files or even da........

Debian Mint Ubuntu Which Package Provides missing top, ps and w Solution

Install procps and it will install the other packages you need: apt install procps Reading package lists... Done Building dependency tree Reading state information... Done The following additional packages will be installed: libgpm2 libncurses6 libprocps7 lsb-base psmisc Suggested packages: gpm The following NEW packages will be ins........

Vbox Virtualbox DNS NAT Network Mode NOT working

There is a random bug that sometimes occurs with Vbox NAT mode DNS, although it has never happened in the past and Vbox was working fine until recently. The symptom is that you can see it does get an IP+ DNS from the Vbox NAT DHCP. Below we use resolvectl dns and verify the DNS server is set to 10.0.2.3 which is the DNS from Vbox NAT. We can ping it but it does not respond to any DNS requests when we use dig @10.0.2.3 realtechtalk.com........

Docker Tutorial HowTo Install Docker, Use and Create Docker Container Images Clustering Swarm Mode Monitoring Service Hosting Provider

The Best Docker Tutorial for Beginners We quickly explain the basic Docker concepts and show you how to do the most common tasks from starting your first container, to making custom images, a Docker Swarm Cluster Tutorial, docker compose and Docker buildfiles.........

How To Create OpenVPN Server for Secure Remote Corporate Access in Linux Debian/Mint/Ubuntu with client public key authentication

Why choose OpenVPN instead of a firewall appliance? OpenVPN can be a reliable and easy replacement for traditional hardware or just be an additional tool that your company uses so that the firewall can focus on its job rather than acting as a VPNappliance at the same time. When comparing OpenVPN with traditional firewal........

Linux Mint 20 cannot install snapd missing solution

The Linux Mint team has disabled it by setting an apt preference, you can edit or just remove the file: sudo apt install snapd Reading package lists... Done Building dependency tree Reading state information... Done Package snapd is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source........

Cisco Howto Configure Console Port/Terminal/Comm Server with Async Cable Setup

This assumes that you've already installed the relevant HWIC cards eg. Cisco Asynchronous Serial NIM These are essentially cards that you install into your router, once installed you connect an Async cable to one of the ports on the card which normally gives you 8 console cables and are normally labelled 1 through 8. You connect all of the cables to the devices you need (even non-Cisco devices) whether switches, routers or firewalls, they will usually work. The real m........

Ubuntu/Debian Linux/Unix Howto Setup Install Syslinux Bootable USB with EFI and MBR from Command Line/CLI Terminal

There aren't too many simple guides that show you how to use commands to setup your USB or other drive as a normal bootable drive where you can easily boot custom kernels or whatever OS you would like. 1. Get the tools we need: We install "syslinux" for MBR and "syslinux-efi" for EFI and "MBR" as we need a tool that embeds the actual MBR into our USB: sudo apt install syslinux syslinux-efi mbr........

Cisco Switch Howto Reset Password

This was done on a 2900 but applies to all the switches of the same era. Step 1 - Power Cycle and enter recovery mode If you have physical access you can power cycle and hold the mode button down for 15 seconds. After that the SYS light will flash on the switch and you will see the following screenshot. If you don't have physical access (eg. it is a datacenter swich over console only) then power cycle and hit "Ctrl+Pause/B........

bash how to hide username/customize prompt Linux Debian Redhat Ubuntu Solution

Just edit your ~/.bashrc and add this at the very end: export PS1="realtechtalk.com" Then your prompt will look like this: bladeblox:uptime 08:47:14 up 48 min, 1 user, load average: 1.00, 1.07, 0.96 If you wanted a dollar sign at the end then you would change it like this: export PS1=&........

Juniper JunOS Command Overview and Howtos Switch, Router, Firewall Tutorial Guide

Enable "cli" mode equivalent in JunOS cli Configure Mode configure So rather than going to the console on a Cisco switch and typing "enable" and then "conf t", the equivalent in JunOS is "cli" and "configure". How Do You Apply Changes You've Made? You can make all kinds of changes to the switch, but remember they are not........

How To Boot, Install and Run Windows 2000 on QEMU-KVM

Interestingly enough Windows 2000 works fine on QEMU 64-bit but you have to specify Pentium as your CPU otherwise it doesn't complete the install (it will not pass the detecting/setting up devices phase). -vga cirrus is wise because it is supported by Windows 2000 and allows higher resolutions and 24-bit color. -cpu Pentium emulates an old computer and is necessary for install to complete -device rtl8139 is important as this oldschool Realtek 8139 NIC is supported by W........

How To Replace Audio Track of Video using ffmpeg

A very common use case is that you don't want to waste time using a video editor that requires you to open it up and manually import the video clip and audio clip, then manually delete the old audio track and import the video and new audio. That's too much work and time since we don't want to go through the hassle. ffmpeg is our solution, all we have to do is specify 3 variables and we're done! -i Windows2019-Server-Noaudio.mp4 is our in........

Linux Mint Ubuntu Debian CentOS Dual Boot Install Issues

The best way to avoid this problem is to understand how your BIOS is setup to boot. Often newer machines will default to U(EFI) which is different than the traditional MBR/Legacy mode. The problem is that this may not be apparent, often a BIOS Boot Menu will show a Legacy Boot Option and EFIOption without defining it. A good example of this is if your USB is called "Kingston" you may see in your Boot Menu "Kingston" and also "Ubuntu"........

Nvidia Ubuntu Linux Screentearing Video with solution driver

This seems to happen on most if not all Nvidia cards but the good news is that if you are using any of the Linux drivers and have the nvidia-settings tool installed it is just a simple command. Solution: nvidia-settings --assign CurrentMetaMode="nvidia-auto-select +0+0 { ForceFullCompositionPipeline = On }" Enter the above command in your terminal and the screentearing will be fixed which is like enabling Tear Free on AMD cards.&........

CentOS 6 impossible to compile a newer libguestfs

yum -y install gcc make gperf genisoimage flex bison ncurses ncurses-devel pcre-devel augeas-devel augeas readline-devel checking for cpio... cpio checking for gperf... no configure: error: gperf must be installed configure: error: Package requirements (augeas >= 1.2.0) were not met: Requested 'augeas >= 1.2.0' but version of augeas is 1.0.0 yum remove augeas augeas-libs augeas-devel wget http://downl........

Linux Ubuntu Debian Centos How To Make a Bootable Windows 7, 8, 10, 2016, 2019 Server USB from ISO

Use fdisk on your USB drive to create a bootable NTFS partition (in my case /dev/sdb): sudo fdisk /dev/sdb Welcome to fdisk (util-linux 2.27.1). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): n Partition type p primary (0 primary, 0 extended, 4 free)........

MySQL Cheatsheet Guide and Tutorial

Create Database: create database yourdbname; Show All Databases: show databases; Change Database: use mysql; Drop / Delete a MySQL Database: drop database nameofyourdatabase;........

gsmartcontrol for Windows to Check the SMART S.M.A.R.T status

gsmartcontrol is a free tool that let's you see the status of the SMART parameters so you can check things like temperature, reallocated sectors, bad sectors etc.. to give you a better idea of your drive health. Download it here. gsmartcontrol is a very useful tool in Windows to check your HDD / Hard Drive health status. In my experience you should NEVER trust that everything is OK just because SMAR........

How To Use Letsencrypt SSL/TLS Encryption to Create Certificates without installing on the target machine

For some reason, perhaps you don't want to run a daemon or let Letsencrypt have access to your production server. There is a way to use it like a normal CSR/CA setup in manual mode. ./letsencrypt-auto certonly --manual -d realtechtalk.com - www.realtechtalk.com Eventually you will get prompted to create a certain path and file with certain data: Create a file containing just this data: Casdfasfadsfsad........

Cisco Router Setup Guide and Tutorial Howto With Commands and Examples

In most of the Cisco router IOS I find the ports like ge0/0 ge0/1 and ge0/2 or whatever your ports are down. They will not even give you a link light. So one of the first tasks should be getting the port you are working with up. In my case the first goal is often connectivity with the LAN and WAN. LAN = your local area network (eg. in the office/home ) WAN= your ISP/public internet (eg. fiber/cable/dsl/ethernet).........

How To Boot Cisco CUCM UCSInstall 8.6, 10, 11 and 12 on KVM/Proxmox

The key thing is that you must use a "machine"id of "pc-1.3" or it will say your hardware is not supported. Additionally you MUST use a virtio disk or you will get a ks_pre.sh error as soon as the install starts (a look at logs will show it can't find a disk). This is funny because even though the OS finds the disk and an fdisk -l shows it, it looks like the script looks for a /dev/vda device (virtio) and nothing else, so if you didn't use Virtio as you........

Linux Mint 18.2 Create Config File To Start Application Upon Login

This is not about systemd/systemctl and not about "onboot" so there's no rc.local trick here but it's the GUI/Gnome etc when a user logs in that a command is launched. Put this in your home dir The .config/autostart directory is where Linux Mint/Ubuntu checks for autostart application config files mkdir -p ~/.config/autostart Create a new entry/file that starts an application........

iptables linux firewall recommended rules for public computing

Whether you are at work, at the coffee shop or on the public internet here are some basic but effective rules for iptables that lock things down (eg. no one can SMB or SSH to you or really anything): # Generated by iptables-save v1.4.21 on Fri Dec 14 14:00:08 2018 *nat :PREROUTING ACCEPT [160:19844] :INPUT ACCEPT [4:357] :OUTPUT ACCEPT [2955:182236] :POSTROUTING ACCEPT [2955:182236] COMMIT # Completed on Fri Dec 14........

How Does Cisco CUCM (Cisco Unified Communication Manager) Work?

Cisco's CUCM (Cisco Unified Communication Manager) is a system that combines voice, video, data and mobile products into a single unified management suite. At its core, the CUCMis like a "Super PBX" that controls the flow of all communications through an organization even single or multiple site deployments. Cisco's CUCMmakes communication more effective and simple through centralized management and unification of communications resources.........

AMD Set Fan Speed and Other Powerplay Memory/CPU Timings with a Linux script

You can do other things but this particular script is just to set all AMD cards to 80% fan speed (remember this script needs to applied everytime you reboot). You could set it is a cron or just throw it into /etc/rc.local basepath=/sys/class/drm for hwmon in `ls -1 /sys/class/drm|grep card[0-99]$`; do echo card=$hwmon; hwmonname=`ls $basepath/$hwmon/device/hwmon|grep hwmon[0-99]` hwmonpath=$basepath/$hwmon/device/hwmon/$hwmonname echo "ec........

VMWare ESXi 6.7 SSH/PowerShell CLI Commands

[root@localhost:~] BootModuleConfig.sh echo host-ind nfcd........

[warn] VirtualHost 10.2.5.101:443 overlaps with VirtualHost 10.2.5.101:443, the first has precedence, perhaps you need a NameVirtualHost directive

[root@thetor2017 conf]# service httpd restart Stopping httpd: [ OK ] Starting httpd: WARNING: MaxClients of 3000 exceeds ServerLimit value of 300 servers, lowering MaxClients to 300. To increase........

Linux How To Free Wasted Memory RAM in Buffers

We all know Linux is known for good memory management but is it really? It seems all on its own with hardly anything running that you can come back in days or weeks and find that almost all of your RAMis used! And many will say "no don't worry it's buffers for optimization" but it doesn't seem to help because what is in buffers is not available to use for new programs running or ones that allocate more RAM as far as Ican tell. The reason Iknow........

VMWare 6.7 VCSA VSphere ESXi Management SSO Install Guide on Linux using the CLI

#mount the VCSA DVD mount /dev/sr0 /mnt/cd #alternatively you could mount the iso directly mount -o loop vcsa.iso /your/mount/path #for this purpose we are using the CLI installer on Linux cd /mnt/cd/vcsa-cli-installer/lin64 #no it's not going to be that easy you can't just run vcsa-deploy like that you need to use a template or configured .json file ./vcsa-deploy Usage: vcsa-deploy [-h] [--version] [--supported-deploymen........

mail command line examples of how to send an email using Linux / Unix and the Bash Shell or Scripting

A simple way that may work for a lot of people who just need basic output for their scripts or daemons to announce an action is this: echo "body or message" | mail -s "realtechtalk.com" user@domain.com If you want to send a text file as the body just do this instead: mail -s "realtechtalk.com" user@domain.com < /tmp/sometxtfile.txt These are some ve........

OpenVPN cannot ping remote IP routing loop issue after connecting

Sometimes if you have a very basic configuration OpenVPN on the client side for some reason sends all traffic to the OpenVPN server IP through the tun0 which is of course impossible and creates a block or routing loop. This is because you need to use your normal ISP/LANgateway to hit the OpenVPN server if it is remote/offsite as is usually the case. So if you are connected to the OpenVPN through say a tun0 device and your routing is set to connect to the OpenVPN&nbs........

vzquota : (error) Quota on syscall for id 4532: No such file or directory vzquota on failed [3] OpenVZ Error and Solution

Starting container... vzquota : (error) Quota on syscall for id 4532: No such file or directory vzquota on failed [3] Solution vzquota drop 4532 Then start the container and it should work. It actually happened after migrating the VPS manually to ano........

Apache htaccess Custom ErrorDocument not working properly for root home page 403 Error Issue and Solution

So I have a domain "testdomain.com". Inside test domain.com's root is the following .htaccess: Options +FollowSymLinks -Indexes ErrorDocument 403 /launch/index.html Order Deny,Allow Deny From All Allow From 192.168.1.2 When you visit anything other than root things work fine. Eg. if you visit http://testdomain.com/somedirfile.html It will show the right error in /launch/........

How To Install Windows Server 7 8 10 12 2008 2012 2014 2016 Servers Desktops using Linux tftp, dhcpd and samba

It has been a big pain for a long-time to install Windows from a Linux environment. I used to run a windows install server and it never worked right for some reason (the install would fail on most servers). Before getting start be sure to setup your samba share so once you boot into WinPE you can mount the install for whatever Windows you want /etc/samba/smb.conf [smbwinstall] path = /tftpboot/images/winstall guest ok = yes........

MySQL Adding New Field to Existing Database Table

ALTER TABLE existingtable ADD newfieldname VARCHAR(255);........

MySQL How To Add New Field Column To Existing Table

ALTER TABLE thetable ADD newfield VARCHAR(255) It's very simple just specify "the table" and then the newfield type........

M2Crypto.SSL.Checker.WrongHost: Peer certificate subjectAltName does not match host, expected fedora-archive.ip-connect.vn.ua, got DNS:mirror.ip-connect.vn.ua

You are using Centos 5 which is deprecated so nothing in yum will work until you follow this post to use the vault: http://realtechtalk.com/Centos_59_Working_Vault_Repo_file-1921-articles yum update Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * epel: fedora-archive.ip-connect.vn.ua Traceback........

rsync specify alternate port non-standard port than 22

It is not obvious but the rsync --help rsync --help|grep port --port=PORT specify double-colon alternate port number --port does not do anything at all actually for some strange reason it still uses 22 You have to specify a manual ssh command to make it work: -e 'ssh -........

ffmpeg how to watermark and concatenate in one command

If you were in my boat you were frustrated that you had to double encode, eg. one separate encode for watermark and a separate from concat and it's not easy to figure out this with ffmpeg on your own. However it is a nice way to save time! ffmpeg -i file1.mp4 -i file2.mp4 -i file3.mp4 -i watermark.png -filter_complex "[0:v]setpts=PTS-STARTPTS[v0]; [1:v]setpts=PTS-STARTPTS[v1]; [2:v]setpts=PTS-STARTPTS[v2]; [v0][0:a][v1][1:a][v2][2:a]concat=n=3:v=1:a=1[v][aout]; [v][3:........

ffmpeg trouble concatenating similar but different files

When things go wrong your video is basically unplayable or the first video plays fine and then freezes when moving on to the next. Generally if both videos weren't produced with the exact 100% same settings you will have issues. You can try the basic concat but it often won't work right. Solution for me: My example uses 3 videos in total so "n=3" and a=1 to include audio. ffmpeg -threads 12 -i file1.mp4 -........

ffmpeg Unable to Use Hardware Encoding with Nvidia 3.40 Driver and GT210 card

I believe from what I've read that this card's driver doesn't support the features after trying all known troubleshooting methods. ffmpeg -i uservideoRendered.mp4 -filter:v hwupload_cuda,scale_npp=w=1920:h=1080:format=nv12:interp_algo=lanczos,hwdownload -c:v hevc_nvenc -profile main -preset slow -rc vbr_hq -c:a copy uservideoRendered.mp4-test ffmpeg -i uservideoRendered.mp4 -filter:v hwupload_cuda,scale_npp=w=1920:h=1080:format=nv12:interp_algo=lanczos,hwdownload........

ffmpeg Linux Mint download, compile and install howto

#if you have nvidia make sure you install the nvidia-cuda-toolkit so hardware acceleration can be used wget http://ffmpeg.org/releases/ffmpeg-3.3.2.tar.bz2 tar -jxvf ffmpeg-3.3.2.tar.bz2 cd ffmpeg-3.3.2/ ./configure --disable-yasm install prefix /usr/local source path ........

cudaminer freezes Linux Mint taints kernel

When running cudaminer once it tries to initialize the card the entire screen freezes. The computer itself is still running but the Xorg is done for, you cannot even switch to another console window and must reboot (even an mdm or Xorg restart does not help). At first cudaminer will give you these errors: stratrum_recv_line failed ...retry after 15 seconds GPU #0: Geforce 210 with compute ca........

Openshot 2.2 is very unstable always crashing in Linux Mint 18.1!

Jun 1 15:45:42 videoeditor-desktop org.mate.panel.applet.MintMenuAppletFactory[1882]: project_data:INFO Missing folder chosen by user: Jun 1 15:45:42 videoeditor-desktop org.mate.panel.applet.MintMenuAppletFactory[1882]: project_data:INFO Removed missing file: MAH02949.MP4 Jun 1 15:45:57 videoeditor-desktop org.mate.panel.applet.MintMenuAppletFactory[1882]: ui_util:WARNING Icon theme media-playback-start not found. Will use backup........

use ffmpeg to watermark videos if mencoder/bmovl fail

If you have this problem: http://realtechtalk.com/mencoder_bmovl_error_vf_bmovl_Unknown_command_Ignoring_-1860-articles Then ffmpeg is for you. Go here if you are using Linux Mint and cannot find or install it to use an external PPA........

Avocent DSR8020 KVM/IP - Network Connect Error - Solution

This error is commonly due to Java security or TLS settings but there is a second issue with forwarded ports that also causes it. 1. Java Security/TLS Settings issue: This article has the solution to change them all in Linux automatically 2. Port Forwarding Issue if your Avocent DSR is behind NAT/private IP........

How to verify SSL SHA-1 Certificate Fingerprnit Signature of your mail/web server to avoid hijacking/man-in-the-middle attacks

This is especially helpful if you run your own servers. If you are presented with an error message or warning that the signature has changed or does not match the IP/domain you are connecting to you always want to verify manually. So your e-mail/web client will show you an SHA-1 fingerprint like this: "Could not verify this certificate because the issuer is unkown" or other reasons such as a mismatch in IP/domain. It will also show you........

Linux Mint Network Manager Connection Disconnect Option Grayed Out

This is a real pain because I had to manually unplug ethernet cables for network testing or to use an alternate network or guarantee physical access to one network segment is cut off. For some reason this happened after Ikilled dbus because it was confused and blocking packets thinking they were coming from the wrong interface since eth0 and eth1 both had the same subnet and gateway. I eventually did a "service network-manager restart" but the option was........

Centos 6 how to guide convert LVM non-RAID into mdadm 1/10 RAID array live without reinstalling

Here is the scenario you or a client have a remote machine that was installed as a standard/default minimal Centos 6.x machine on a single disk with LVM for whatever reason. Often many people do not know how to install it to a RAID array so it is common to have this problem and why reinstall if you don't need to? In some cases on a remote system you can't easily reinstall without physical or KVM access. So in this case you add a second physical or disk or already ha........

Firefox errors Unable to generate public/private key pair. (Error code: sec_error_keygen_fail)

Your firefox is out of date if you get errors like below: Secure Connection Failed ........

HP Procurve Switch 2824 CLI Telnet Experience , Guide and Tutorial

------------------------------------- ProCurve J4903A Switch 2824 Software revision I.10.77 Copyright (C) 1991-2009 Hewlett-Packard Co. All Rights Reserved. RESTRICTED RIGHTS LEGEND Use, duplication, or disclosure by the Government is subject to restrictions........

OpenVZ vzctl update changes how iptables work - iptables v1.3.5: can't initialize iptables table `nat': Table does not exist (do you need to insmod?) Perhaps iptables or your kernel needs to be upgraded. updated solution

Are you getting the same old error message even though your iptables settings for OpenVZ are correct? iptables v1.3.5: can't initialize iptables table `nat': Table does not exist (do you need to insmod?) Perhaps iptables or your kernel needs to be upgraded. The reason is because in newer vzctl the old way of setting IPTABLES="" in vz.conf is completely deprecated (I spent some time fiddling wondering why my settings were correct but........

esniper and curl errors https://signin.ebay.com/ws/eBayISAPI.dll?SignIn: Couldn't connect to server: couldn't connect to host

I kept thinking it was esniper but somehow my bash settings have a preset proxy that was creating the issue. https://signin.ebay.com/ws/eBayISAPI.dll?SignIn: Couldn't connect to server: couldn't connect to host curl manually to any URL is the same: curl: (7) couldn't connect to host Run curl with -vvvvvv mode to see the issue: curl -vvvvvvvvvv http://realtechtalk.com * About to c........

Postfix how to secure outgoing authenticated e-mails for privacy and hide the IP address, mailer and other things

The most common solution is to use the /etc/postfix/header_checks but this is a big problem. Why is header_checks a problem? Because it does it to all mail whether incoming or outgoing and whether authenticated or not. We of course want as much header information for incoming as we can get for many reasons but many organizations want to secure and make their mail clients as secure as possible. I adapted this solution to the client's custom config, they are configur........

Samsung Galaxy Note Upgrade/Update Experience from 4.0.4 with aftermarket ROMs

It really seems that 4.4.4 is not ready or stable for the i717 yet and this makes sense since it takes a lot of work/development and testing to get the factory stock ROMs working well. In the end I used the 4.1.2 based Blackstra BlackJelly because it was fast, stable and just works and feels great. The aftermarket support is great but many devs are focussed on adding features and customization that most of us don't want or need rather than getting things smooth and stable.........

CPanel Link to all of the command line options

CPanel says you can access 98% of the functions through CLI which experienced Unix/Linux admins prefer for simplicity and for scripting. I've never found CPanel easy to use from the admin panel, it seems everything is hard to find and a simple task becomes a series of hunts. So for people like me here's the list: http://cpanel.net/system-administrators/command-line-scrip........

virtio KVM drivers download location

http://realtechtalk.com/downloads/virtio-win-0.1-74.iso Current Direct stable URL from Fedora: https://fedoraproject.org/wiki/Windows_Virtio_Drivers Direct Downoad of Stable Virtio: https://fedorap........

cPanel VPS Server Cannot Login as root

I was worried the server was hacked, I was logged in already as root but couldn't login to CPanel or a new SSHsession. I even reset the password from the shell and it did not work still. The reason is CPanel Hulk, it detected a brute-force attack so it locked down the root account entirely even from the correct password. According to cPanel the best way around this is to whitelist your IP.........

MySQL How to add a field/column using alter

ALTER TABLE yourtable ADD COLUMN info VARCHAR(255)........

Asterisk iptables block bruteforce attacks howto with fail2ban

yum -y install fail2ban vi /etc/fail2ban/jail.conf [asterisk-tcp] enabled = true filter = asterisk action = iptables-multiport[name=asterisk-tcp, port="5060,5061", protocol=tcp] sendmail-whois[name=Asterisk, dest=you@example.com, sender=fail2ban@example.com] logpath = /var/log/asterisk/messages maxret........

wget test without actually downloading howto

user the "--spider"switch and you can see what it would do. wget -r --spider dontryrealtechtalk.com........

vzquota : (error) Quota on syscall for id 42131: No such file or directory vzquota on failed [3]

Starting container... vzquota : (error) Quota on syscall for id 42131: No such file or directory vzquota on failed [3] Solution cd /var/vzquota mv quota.42131 quota.42131-disable vzctl start 42131 Starting container... Initializing quota ... Container is mounted Adding IP address(es): Setting CPU units: 1000 Container start in progress... ........

LSI MegaRAID Adventures, Guide and HowTo

LSi Megaraid At first it was configured as a RAID 0, then I deleted the Virtual Disk Group. I thought both drives would be shown and detected in Linux as sda and sdb but it actually shows nothing. To make them work you have to hit Ctrl+R before the system boots (when prompted) and create a Virtual Disk Group. In my case I created each one as RAID 0 (with a single drive only) as I just wanted JBOD but there is no such option or default in these Dell Pe........

mkdir(): Too Many Links - The Solution and Problem in ext3 filesystems

The error itself "mkdir(): Too Many Links" is not very useful, but I'll translate it into plain English. It means you've reached the filesystem's limit of how many directories can be created in a single directory. In this case for ext3 the limit is 32000 and it was exceeded. What's the solution? The simple solution is to move those directories into more subdirectories possibly sorting them by date, alphabet or numerically.........

How to log all PHP based E-mails for abuse

Step #1 - Create Wrapper Script vi /usr/local/bin/phpsendmail #!/usr/bin/php ........

iptables v1.4.10: can't initialize iptables table `filter': Table does not exist (do you need to insmod?)

I have iptable_filter loaded on the hostnode so I don't understand this issue.........

Centos 6 RTL8111/8168B r8169 link up and down error solution/fix

02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03) For whatever reason it seems the r8169 driver that ships and has shipped with most Linux distros for years is still flawed and does not work properly on these cards, causing 100mbit connectivity when it should be 1gbit and even worse, causing random network dropouts. The r8169 driver in Linux kernels is simply not meant to be used on th........

How to install GRUB to the MBR of a disk image.

cat | grub --device-map=/dev/null Now pay close to the attention of the beginning. Type: "device (hd0) VPS.img" this is telling what hd0 will be to GRUB and we're telling it the disk image file "VPS.img" in the current directory is hd0, you can specify alternate paths and image names of course. GNU GRUB version 0.97 (640K lower / 3072K upper memory) [ Minimal BASH-li........

Thunderbird How-To Copy/Backup/Restore Accounts and Settings to Another Computer

The best way is to use rsync, I've set it up so it doesn't copy unnecessary files, or at least ones I'm sure aren't needed. Here is the rsync command Iused (adapt to your specific Thunderbird profile location): rsync -hazv user@remotehost.com:/home/user/.thunderbird/sbrer.default/* /home/user/.thunderbird/4nyb0.default/ --exclude=global* --exclude=Cache --exclude=ImapMail --exclude=Mail This is a great way to get your e-mail accounts going on a new c........

mdadm: /dev/sdb1 not large enough to join array solution

mdadm --manage /dev/md1 --add /dev/sdb1 mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: /dev/sdb1 not large enough to join array md1's first primary member /dev/sda3 has 57394 cylinders while the /dev/sdb1 has 57393 (1 less cylinder) which is why it won't work. fdisk -l /dev/sda3 Disk /dev/sda3: 47........

ip_conntrack: table full, dropping packet. solution for Linux RHEL/Centos/Debian

ip_conntrack: table full, dropping packet. A lot of clients I've seen have this issue, it really seems the default level is way too small. Once this connection tracking table becomes full then packets get dropped which is obviously a bad thing. One thing to be mindful of though is that 350 bytes of memory are used per entry so there is some justification for not keeping it too high. However, if you have multiple servers running or high traffic daemons........

bash script remove non-printable special characters/white space

In bash you test like this for problems that can be caused by non-printable characters since if you don't know how to identify it because it basically breaks your script. echo "url=$url" should print something like this normally if you have properly formatted input/text: url=::http://someaddress.com:: But if you have some weird hidden characters (not visible in a text editor of any sort you'll get something like this ::l=::http://s........

iptables v1.3.5: can't initialize iptables table `nat': Table does not exist (do you need to insmod?) - OpenVZ Container Problem iptables module problem solution

iptables v1.3.5: can't initialize iptables table `nat': Table does not exist (do you need to insmod?) This solution applies to all other iptables modules/problems for OpenVZ, you'll just need to add them to both lists/lines below if you have modules other than what I have below. The modules need to be enabled in both iptables and the OpenVZ hostnode itself and then the containers which need it must be restarted. How To Enable IPTables Modules in OpenVZ........

Linux Ubuntu Nvidia GT430 Lockups/Errors/Freezes NVRM: os_schedule: Attempted to yield the CPU while in atomic or interrupt context

I'm running Ubuntu 10.10 with Asus NVIDIA GT430 2.6.35-32-generic-pae #65-Ubuntu SMP Tue Jan 24 14:06:16 UTC 2012 i686 GNU/Linux Nvidia binary driver: 260.19.06 The screen sometimes completely freezes and locks up or everything starts going very slow: [1903398.100007] NVRM: os_schedule: Attempted to yield the CPU while in atomic or interrupt context [1903402.373210] NVRM: Xid (0001:00): 53, CMDre 00000000 00000080 00000000 00000005 00........

Xen non-HVM container won't work/boot anymore

One of my test Centos 5 containers was on a partition that filled up and it threw all sorts of errors and stopped responding but now I can't boot it again anymore. All the console shows is the Linux Penguin on the top left corner and the xm console says "usbcore: registered new driver hub" and has halted there. Centos 5 Xen container stuck/frozen won't boot on "usbcore: registered new driver hub" Another great way of troubleshooting is booting fro........

How to view UDP and other protocol connections?

netstat is weak and can't show udp connections and most other protocols, use "ss" which is what netstat should have been: The "-u" switch stands for udp, here's a list of other options: Usage: ss [ OPTIONS ] ss [ OPTIONS ] [ FILTER ] -h, --help this message -V, --version output ver........

List of Free Public DNS Servers IP Addresses

One thing to note about DNS servers and providers is that they aren't always trustworthy, not even if they're Google or your favorite ISP. Any DNS server can compromise your privacy, and they are likely tracking your browsing habits and keeping logs of it. Sometimes it's for Marketing/Research purposes such as Google's GMail service which they admit is scraped/datamined. I would expect nothing less from their DNS service. The other danger with such widely used and pu........

Convert PDF to JPG/JPEG without low resolution/small picture size

convert -density 400 somepdf.pdf -scale 2000x1000 output.jpg The key is the "-density 400" switch and also -scale 2000x1000 To give credit I found the solution here: http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=10928 That was the perfect solution when I was frustrated with how small the resulting JPG's resulted. I'm sure this will help a lot of people when it comes time to converting a PDF to JPG which I'm amazed Imag........

Enable SPAMASSASSIN on Postfix in 5 minutes

Centos 5 Postfix and SPAMASSASSIN Tutorial yum install spamassassin chkconfig spamassassin on vi /etc/mail/spamassassin/local.cf ############## #required_hits 5 #report_safe 0 #rewrite_header Subject [SPAM] #5 is the least restrictive (means only the most obvious SPAM is caught. 0 is obviously the most restrictive/sensitive and would have lots of false positives require........

Thunderbird copy filters to other accounts

cp msgFilterRules.dat /other/mail/folder edit msgFilterRules.dat change all instances of your old mailbox: actionValue="mailbox://joes@mail.server.com/name" to: actionValue="imap://joes%40server.com@mail.server.com/INBOX" sed s/'actionValue="mailbox:joes@mail.server.com'/imap://joes%40server.com@mail.server.com/g msgFilterRules.dat-........

CPU #1 not responding - cannot use it.

I think this will be useful to others because I have a server that kept crashing mysteriously during intense disk usage/RAID checks. It would only crash during the weekly RAID integrity check. ThenI noticed during a reboot that not all CPUs were being brought up, as a result this actually creates much higher temperatures with the output I got from sensors, just booting the system produced higher than normal temperatures. You can imagine that a full blown RAID check........

Understanding /etc/aliases from sendmail when using with postfix or other MTA's

understanding /etc/aliases *remember to apply changes you need to run "newaliases" after editing /etc/aliases one thing I don't get is that it doesn't allow you to specify the whole e-mail address on the left-hand side eg: yourfullemail@domain.com: someotheremail@domain.com postalias: warning: /etc/aliases, line 109: name must be local (if you try the above) It works more like this: your........

Linux Realtek Gigabit NIC huge/high latency problem after sleep?

That is pinging to the gateway IP on the same switch, the same IP is pingable externally without any problems which makes me think the switch is fine. 64 bytes from 55.55.55.55: icmp_seq=4 ttl=255 time=1.07 ms 64 bytes from 55.55.55.55: icmp_seq=1 ttl=255 time=3536 ms 64 bytes from 55.55.55.55: icmp_seq=2 ttl=255 time=2536 ms 64 bytes from 55.55.55.55: icmp_seq=3 ttl=255 time=1536 ms 64 bytes from 55.55.55.55: icmp_seq=8 ttl=255 time=1.20 ms 64 by........

Ubuntu 10.04 Linux is still not ready for the Desktop world

I am a huge fan of Linux and the idea of OpenSource but I've said it many times, there are still hurdles in today in 2010 for Linux as a Desktop. Linux is still intended for servers at its very core. This can be changed succesfully though, as Apple has shown us with Mac OS X based on FreeBSD. Half of the issue is lack of driver support and the other half is the Linux Kernel and Window Manages, KDE and GNome still both don't cut it (but they're getting closer). I'll........

md: kicking non-fresh sda1 from array! - fix/solution

md: Autodetecting RAID arrays. md: autorun ... md: considering sdb1 ... md: adding sdb1 ... md: adding sda1 ... md: created md0 md: bind md: bind md: running: md: kicking non-fresh sda1 from array! md: unbind md: export_rdev(sda1) raid1: raid set md0 active with 1 out of 2 mirrors The md0 raid kicked sda1 ou........

Realtek r8169 1gbit/1000mbit NIC/Ethernet Goes Down/Halts on Large File Transfer/Heavy Network Usage

This is obviously a bug in the r8169 kernel module and it seems to affect a lot of people. I upgraded to the latest kernel and hope this won't happen anymore, as it is a very serious error. This is especially serious for those who are running servers with this chipset, who can afford for the NIC to randomly go off-line for no apparent reason? [655548.189113] type=1505 audit(1277067560.902:5): operation="profile_load" name="/usr/bin/freshclam&q........

How To Set DHCP/Static IP Address in Centos/RHEL/Fedora & Debian/Ubuntu/Kubuntu/MEPIS Set DHCP/Static IP Address

Basically the two main types of distros are Debian and RHEL/Centos based. I'm just going to give a quick overview of how the configuration of IP interfaces works in Debian/Centos based distros. *Just one thing to remember, when setting IPs statically you have to manually specify a DNS server in /etc/resolv.conf (since DHCP is what normally does it automatically) Debian/Ubuntu/Kubuntu/MEPIS The IP (DHCP &........

Openvz Enable Most Common iptables modules

The default options for iptables are very basic. Here is what you need to do in order to enable them in OpenVZ. 1.) Add the modules to iptables and restart iptables: vi /etc/sysconfig/iptables-config Edit the line as so: IPTABLES_MODULES="ipt_REJECT ipt_tos ipt_TOS ipt_LOG ip_conntrack ipt_limit ipt_multiport iptable_filter iptable_mangle ipt_TCPMSS ipt_tcpmss ipt_ttl ipt_length ipt_state iptable_nat ip_nat_ftp" 2.........

SSH Automatic/Passwordless Logon - Setup Public Key Encryption In Single Command

This is a very simple solution, but most guides out there make you login twice (once to scp the key) and once to put the key in authorized_keys. There's no need for that. If you don't already have a ~/.ssh/id_rsa.pub just type "ssh-keygen -t rsa" and keep hitting enter until it's done :) Just use this code to easily enable passwordless login with SSHD key=`cat ~/.ssh/id_rsa.pub`;ssh user@192.168.5.25 "echo $key >> ~/.ssh/auth........

rsync halted froze Out of memory: kill process 7559 (rsync) score 635 or a child Killed process 7559 (rsync)

Out of memory: kill process 7559 (rsync) score 635 or a child Killed process 7559 (rsync) I was surprised to see this in my dmesg whenmy rsync backup suddenly stalled/stopped. This system has 3 gigs of RAM and lots of free memory so I don't understand what is happening. rsync invoked oom-killer: gfp_mask=0x200d2, order=0, oomkilladj=0 Pid: 7600, comm: rsync Not tainted 2.6.24.2 #83 [] oom_kill_pr........

MySQL TEXT field size length limit reminder, don't truncate your data!

I thought there would be an error message or warning from MySQL in the case that the text you submit is greater than the allowed limit based on the field. So essentially I submitted text that was about 120,000 characters long, whereas the limit of TEXT is just 65,535 characters! I almost lost half of my data/what I typed without knowing it! I just altered the field type in my database from TEXT to LONGTEXT. I can't see how LONGTEXT wouldn't be long enough for MOST........

tar gzip: stdout: File too large - Error Size Limit on Large file > 17GB

The folder I was trying to archive is about 72GB, but much like rsync at about 17GB it chokes because of the filesize. What's with so many common and essential Linux tools having such limitations? I guess it is likely that the authors never wrote their code with the idea that files would be so large but it's still very annoying. It's important to stay on top of these limitations on production servers because I didn't realize what happened until I checked the file with "........

Compaq V2405CA Laptop - Unixbench Performance Test

Here are the results, it is Sempron 3000+ AMD Mobile, 500Gig HDD, 512MB RAM with shared ATI Radeon graphics. # # # # # # # ##### ###### # # #### # # # # ## # # # #&nb........

PHP cannot access /usr/bin/openssl

PHP cannot access /usr/bin/opensslI have verified the username that runs the process is able to access /usr/bin/openssl and it does exist but the PHP script is saying it doesn't exist: [code:1:1fd0f3abbe] if (!file_exists($OPENSSL)) { //echo "ERROR: OPENSSL $OPENSSL not foundn"; }[/code:1:1fd0f3abbe] I don't get itI can clearly see the contents of /usr/bin by using the PHP system fu........

Telus + 2Wire 2700 Router Horrible

Telus + 2Wire 2700 Router HorribleWell first of all let me say this is the only router/switch that sometimes seems to crash/disconnect computers on the local network. This device also thought it would be smart to block VOIP packets coming from my Sipura ATA VOIP adapters so I disabled the [quote:cb89ba7bff]"Invalid TCP Flag Attacks (NULL/XMAS/Other)"[/quote:cb89ba7bff] option Then all of a sudden I couldn't get onto any web pages, the wireless........

Changing field names

Changing field names[quote:91ea6831b6]ALTER TABLE [u:91ea6831b6]table_name[/u:91ea6831b6] CHANGE [i:91ea6831b6]existing_field_name[/i:91ea6831b6] [b:91ea6831b6]new_field_name[/b:91ea6831b6] INT(11);[/quote:91ea6831b6]........

REMOVE a field

REMOVE a field[quote:effdb203d8]ALTER TABLE table_name DROP field_name[/quote:effdb203d8]........

Create Table with structure of another existing table

Create Table with structure of another existing tableOk, this has many valid uses such as if you need to create backups or the ability to undo changes, you would want to create new tables with the same structure as another. Here is how you do it. [i:7ed9581493] Also remember Indexes such as PRIMARY KEYS [b:7ed9581493]will not be preserved[/b:7ed9581493] so you will have to readd them manually.[/i:7ed9581493] [code:1:7ed9581493]CREATE TABLE NewName AS SEL........

ADD PRIMARY KEY to Table

ADD PRIMARY KEY to TableHere is an example of readding a PRIMARY KEY with an AUTO_INCREMENT field: [b:40986c2a8b]First make the field NOT NULL[/b:40986c2a8b] [code:1:40986c2a8b] ALTER TABLE tableName MODIFY FieldNAME INT(18) NOT NULL; [/code:1:40986c2a8b] [b:40986c2a8b]Create The Primary Key[/b:40986c2a8b] [code:1:40986c2a8b]ALTER TABLE tableName ADD CONSTRAINT PRIMARY KEY(FieldName);[/code:1:40986c2a8b........

Basic Port Listing

Basic Port ListingHopefully someone finds this useful or at least interesting. http://www.sans.org/top20/#u9 Name Port Protocol Description Small services ........

RTL8111/8168B R8169 Gigabit Link slow speeds

This is the Intel Atom 330 motherboard with integrated Realtek Gigabit NIC (Intel Desktop Board D945GCLF2 Motherboard W/ Atom 330 1.6 GHz Dual Core Processor - Mini-ITX) I cannot achieve more than 15 MB/s, even doing a local transfer through eth0 to it's own IP. 100% 95MB 15.9MB/s 00:06 So this is not a cabling, switch or hardware issue, it seems like a driver or chipset limitation problem. Here is my........

OCFS2 crash

When trying to even cd or ls the mounted OCFS2 partition it crashes. Ithink this is a combination of VMWare Server's problem and the way I mounted and symlinked to it. More than anything this shows the problem and lack of forsight with VMWare, but also that OCFS2 is easily crashed if you do strange things. Output of /var/log/messages for OCFS2 Apr 10 15:57:45 localhost kernel: [84331.691258] Modules linked in: vmnet vmci vmmon ocfs2_stac........

Viewing and Connecting to an SMB Samba Share on Windows/Linux/Unix

This will give you the basic info needed to browse and connect to Samba shares from the command line. From the GUI of Gnome or KDE etc, it is pretty standard and straight forward. However, I've found very little guides on how to do it from the command line and if you're like me, a nerd who prefers command line for its simplicity and for remote use, this is the way to go. First get a list of all the Samba/SMB shares on the target. smbclient -L hostname........

Welcome to realtechtalk.com

We have years of knowledge with technology, especially in the IT (Information Technology)industry. realtechtalk.com will always have fresh and useful information on a variety of subjects from Graphic Design, Server Administration, Web Hosting Industry and much more.........