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Debian / Ubuntu

Linux Iptables Delete postrouting Rule Command

I am a new Linux server sysadmin. I need to delete POSTROUTING rule. How do I delete postrouting rule on Linux server?
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Sysadmin because even developers need heroes!!!

10 Ubuntu / Debian Linux apt Command Examples

ip-command

I am a new Linux system admin user. How do I use apt command line utility for the package management on Ubuntu Linux LTS and Debian Linux server? How can I use the apt command for the package management?
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How to gzip and keep original file on Unix or Linux command line

I would like to compress a log file using gzip Unix command line utility, and I would also like to keep the original file. However, when I use the gzip my-app.log command, results in modifying my log file and renaming it my-app.log.gz. How do I force the gzip command to keep original file while maintaining the original file on Linux or Unix-like system?
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How to check Debian/Ubuntu Linux package version using apt-get/aptitude command

I am a new Debian / Ubuntu Linux sysadmin. I would like to find out what version I would install if I ran the apt-get command. How do I find out which versions of a package can I install using apt-cache/apt-get command? How do you check package version using apt-get/aptitude on Debian or Ubuntu Linux server?
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KVM libvirt assign static guest IP addresses using DHCP on the virtual machine

I am using KVM/libvirt on Linux operating system and how do I assign static IP address using dnsmasq dhcpd server for my default virtual network switch?
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How to copy permissions from one file to another on Linux

I need to copy or clone file ownership and permissions from another file on Linux. Is there a bash command line option to clone the user, group ownership and permissions on a file from another file on Linux operating system?
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How to configure Nginx with free Let’s Encrypt SSL certificate on Debian or Ubuntu Linux

How do I secure my Nginx web server with Let’s Encrypt free ssl certificate on my Ubuntu Linux 14.04 LTS or Debian Linux 8.x server?
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How to run a command or script after running apt-get command on a Debian or Ubuntu Linux

How do I run custom command after ‘apt-get upgrade‘ or ‘apt-get dist-upgrade‘ on a Debian or Ubuntu Linux based system? How do I hook a script to apt-get command on my Ubuntu Linux server?
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A stack-based critical buffer overflow was found in the way the libresolv library (glibc) performed dual A/AAAA DNS queries. A remote attacker could crash or, potentially, execute code running the library on Linux. How do I patch and protect my server or workstation against the glibc getaddrinfo on Linux operating system?
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How to reload sysctl.conf variables on Linux

I am new Linux system user. How do I reload all sysctl variables without rebooting my server?
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