HowTo: Prevent Yum From Upgrading The Kernel On a CentOS / Red Hat Enterprise Linux

I am a new RHEL / Centos Linux server admin. I would like yum to update all packages except the Linux Kernel. How can I prevent yum command from updating kernel on a CentOS/RHEL/Fedora Linux based systems?

You can prevent yum command from updating the Kernel permanently by following the simple steps.

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Unix / Linux: Check New Files In File System /var/www/uploads/

Recently, I switched from MS-Windows based web-server to CentOS Linux based Apache web-server. All user uploaded files are stored in /var/www/uploads/ directory. Is there command that can give me a list of files that have been added to the filesystem at /var/www/uploads/ in last 7 days on Linux/Unix-like oses?

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Linux / Unix: Check Last Time User Logged In On The System

am a new Unix system admin. How do I find ouw who has recently use the Linux or Unix-like server? Which terminals they used, and when they logged in and out of the my server?

You need to use last command. This command displays last logins of users and ttys.

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CentOS / RHEL: Yum Lock Package Version At a Particular Version

I am a new CentOS / RHEL 6.x server user and DevOP. I need to lock a package called nginx on a server being updated via yum command. How do I lock package version at a particular version on CentOS / Red Hat Enterprise Linux (RHEL) 6.x or Fedora Linux?

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CentOS Linux 5/6: Change OpenSSH Port Number

I am a new CentOS Linux user. How do I change default sshd tcp port # 22 to 2022 on CentOS Linux version 5/6?

You can set or specifies the port number that sshd server listens on. The default is TCP port # 22

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Linux / Unix: whereis Command Examples

Iam a new Linux and Unix-like system command line user. How do I find and locate the binary, source, and manual page files for a given command?

You need to use the whereiscommand to find the source, binary, and manuals sections for specified commands or files.

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Nginx: Redirect Backend Traffic Based Upon Client IP Address

I have four Apache backend servers in front of nginx reverse proxy server. How do I make sure nginx reverse proxy load balancer always send specific client IP address (say IP 1.2.3.4) request to http://apachereadwrite/ backend and rest to http://apachereadonly/ backend?

Nginx web server does support if conditionalconfiguration. You can redirect and/or select configuration depending on client ip address. In this case you need to use the variable called $remote_addr which can be used to retrieve information about the users ip address. This is useful if you want to give file upload capabilities to your own office IP address and read-only capabilities to the rest of the world based upon client IP address or vpn address:

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