ag@linux:~$

System administration

13 posts, oldest first.

  1. Partition, Format and Mount a New Disk with fdisk. How I partition a new disk with fdisk, format it as ext4 and mount it via /etc/fstab, with corrected steps, UUIDs and a warning on picking the right disk.
  2. How to Set Up MySQL Master-Slave and Master-Master Replication. Step-by-step notes for MySQL replication between two servers: my.cnf settings, a replication user, a locked dump, and CHANGE MASTER TO.
  3. How to Install Redmine on CentOS 6 with Apache and Passenger. My notes from installing Redmine 1.4 on CentOS 6.3 with MySQL, Ruby gems, Passenger and an Apache virtual host, with corrected commands.
  4. Basic Linux Administration: Users, Groups and Permissions. Notes on creating users and groups, adding users to groups, reading and changing file permissions with chmod, and what /etc/shadow and /etc/group hold.
  5. How to Install and Configure NFS and NFSv4 on CentOS 6. Setting up an NFS server on CentOS 6, exporting a folder to a client, mounting it with NFS or NFSv4, keeping it after reboot and checking statistics.
  6. Common Linux Log Files and What Each One Records. A list of common files in /var/log and what they contain, with the Red Hat vs Debian/Ubuntu differences and how to read logs with journalctl today.
  7. Use Cron to Sync the System Time with ntpdate. A daily cron job that syncs the clock with ntpdate, with each option explained, the missing server fixed, and today's chrony and timesyncd alternatives.
  8. How to Troubleshoot Apache: A Step-by-Step Checklist. A checklist for when an Apache website will not load: DNS, service status, config syntax, error logs, listening ports, the firewall and SELinux.
  9. Rsync over SSH and the Trailing Slash Question. Copying folders between servers with rsync over SSH, using a custom port and key, and how a trailing slash on the source changes where files end up.
  10. Basic Linux Commands Revisited: mv, mkdir, less and useradd. My 2017 cheat sheet of everyday commands (mv, mkdir, less, rm, useradd, userdel), corrected, with how to read files in less and manage user accounts.
  11. How to Create a Cron Job with crontab. The five crontab time fields and their allowed values, how to add jobs with crontab -e and list them with crontab -l, and worked schedule examples.
  12. Check Running Processes, Login History, Services and Open Ports. Quick commands to see what a Linux server is doing: ps aux for processes, last for login history and netstat or ss for listening ports and services.
  13. Opening Firewall Ports with iptables. Opening ports 80, 110 and 143 by editing /etc/sysconfig/iptables, restarting the service and checking the rules, plus firewalld and ufw equivalents.