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Debian / Ubuntu

A very serious security problem has been found in the Linux kernel. A 0-day local privilege escalation vulnerability has existed for eleven years since 2005. This bug affects all sort of of Android or Linux kernel to escalate privileges. Any user can become root in less than 5 seconds. The bug has existed since Linux kernel version 2.6.22+. How do I fix this problem?
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How to create snapshot in Linux KVM VM/Domain

Before upgrading my virtual machine, I would like to make a snapshot. I want to revert a domain/VM to a snapshot if something goes wrong with my upgrade. Is there a command to create a snapshot of virtual machine (VM) while it is running? Does qemu-kvm support live snapshot creation?
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How to force users to use secure passwords on Ubuntu/Debian Linux

My Linux shell user can modify their password using the passwd command. How can I force users to choose the secure password that will prevent users from using stupid passwords like “abc123”, “password”, “123456” and so on? How do I setup password quality requirements on my Debian or Ubuntu Linux server?
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How to configure Postfix relayhost (smarthost) to send eMail using an external smptd

How do I configure Postfix MTA to send eMail using an external cloud-based SMTP server (with username: password) from a web server on Linux or Unix-like system? How do I configure an Ubuntu server and postfix as the relay server (smarthost)?
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cron Error: bad username; while reading /etc/cron.d file on Linux

I am getting the following error in my cron job log file /var/log/cron.log:
       Aug 22 01:59:01 server2 cron[7510]: Error: bad username; while reading /etc/cron.d/backups
I have job entry as follows to run a job at 00:50 every day for root user:
       50 0 * * * /etc/cron.d/backups
How do I fix this problem on Linux or Unix-like system?
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How to make disk image with dd on Linux or Unix

How do I create disk image using dd command? How do I perform disk cloning from a live Linux cd for backup or recovery purpose?
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How to create RAID 10 – Striped Mirror Vdev ZPool On Ubuntu Linux

How do I create zfs based RAID 10 (striped mirrored VDEVs) for my server as I need to do small random read I/O. How can I create striped 2 x 2 zfs mirrored pool on Ubuntu Linux 16.04 LTS server?
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How to setup a UFW firewall on Ubuntu 16.04 LTS server

How do I setup a firewall with UFW (uncomplicated firewall) on an Ubuntu Linux 16.04 LTS server to restrict traffic on my personal web-server that hosts my pictures and blogs for my family members?
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Linux how long a process has been running?

I‘m a new Linux system user. How do I check how long a process or pid has been running on my Ubuntu Linux server?
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How To Setup Bonded (bond0) and Bridged (br0) Networking On Ubuntu LTS Server

I want to setup KVM bridge with bonding on Ubuntu Linux 16.04 LTS server. I have total four Intel I350 Gigabit network connection (NICs). I would like bonding/enslaving eth0 through eth2 into one bonded interface called bond0 with 802.3ad dynamic link aggregation mode. How do I configure bridging and bonding with Ubuntu Server 16.04 LTS?
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