Anecdotes from a Linux Systems Administrator. /root

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July 17, 2015

BIND - Typo caused slave zone transfer to stop working

by Alpha01

I was surprised to see a typo had caused all slave transfers to shit themselves. I came across a situation where a new slave zone was specified to a non-existing location in the file system and that caused the rest of the slave zones to get permission denied errors when trying to update.


Jul 12 03:23:27 ns2 named[1184]: dumping master file: etc/zones/tmp-Zbk9acg9uv: open: permission denied
Jul 12 03:27:50 ns2 named[1184]: dumping master file: etc/zenos/tmp-4yxBXaUMTq: open: file not found
Jul 12 03:29:46 ns2 named[1184]: dumping master file: etc/zones/tmp-KPqzHa9ev9: open: permission denied
Jul 12 03:38:02 ns2 named[1184]: dumping master file: etc/zones/tmp-kuhtUPjcAi: open: permission denied
Tags: [ bind ]
July 13, 2015

Running my own Git server: GitList

by Alpha01

For the longest time I’ve been wanting to streamline updates to my sites, ie. implement good software deployment technique and procedures. To be specific, start using Git for source code management, and Jenkins to deploy. No, I’m not drinking the whole Agile Kool-Aid. After all we’re in 2015, and people who still continue to use FTP/SFTP to push out changes to their sites should really need to be practicing more long term sustainable procedures. Setting up a git server is really simple. See

Git workflow

I prefer to only communicate with Git over ssh and not https. Since I don’t use the default ssh port, the initial repository clone looks like this:

git clone ssh://$GIT-USER@$GIT-SERVER:$SSH-PORT/home/git/$REPO

GitHub has become the defacto Git hosting provider. I think much of it’s success, aside from the fact that Git is an amazing piece of software, is GitHub’s polished web user interface. While Git ships with a daemon that provides a visual look at the repositories, it’s definitely not pretty. I wanted to have a local GitHub like interface on my private git repos, so I decided to use GitList. GitList is fairly minimalistic. Requiring just PHP and mod_rewrite, it allows you to browse your repositories, view files under different revisions, commit history and diffs. Configuring GitList is really easy.

git clone
cd gitlist
chmod 777 cache
mv config.ini-example config.ini

Then update config.ini to point to the location where the Git repositories are stored in the server. On my server, they’re located in /home/git.

repositories[] = '/home/git/';

Lastly, is just configuring the web server’s virtual host. Since I use Apache mine looks like this.


        DocumentRoot /var/www/gitlist

        <Directory "/var/www/gitlist">
                AllowOverride All
                AuthType Basic
                AuthName "Git Repos"
                AuthUserFile /home/svn/.htpasswd
                Require valid-user

        SSLEngine on
        SSLCertificateFile /etc/httpd/certs/
        SSLCertificateKeyFile /etc/httpd/certs/
        SSLCACertificateFile /etc/httpd/certs/rubyninjaCA.crt

        ErrorLog logs/git_ssl_error_log
        CustomLog logs/git_ssl_request_log \
                "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"



Tags: [ php git apache ]
July 7, 2015

Git Ansible Playbooks

by Alpha01

One of the reasons I love Ansible over any other config management tool is because of its simplistic design and ease of use. It literally took me less than 15 minutes to write a set of playbooks to manage my local git server.

git_server_setup.yml - configures base server git repository configuration.

- hosts: git
  - name: Installing git package
    yum: name=git state=latest

  - name: Creating developers group
    group: name=developers state=present

  - name: Creating git user
    user: name=git group=developers home=/home/git shell=/sbin/nologin

  - name: Updating /home/git permissions
    file: path=/home/git mode=2770

create_git_user.yml - creates local system git user accounts.

- hosts: git

  - name: Creating new git user
    user: name={{ user_name }} password={{ user_password }} home=/home/git shell=/usr/bin/git-shell group=developers

  - name: "user_name"
    prompt: "Enter a new git username"
    private: no

  - name: "user_password"
    prompt: "Enter a password for the new git user"
    private: yes
    encrypt: "sha512_crypt"
    confirm: yes
    salt_size: 7

create_git_repo.yml - creates an empty bare git repository.

- hosts: git

  - file: path=/home/git/{{ repo_name }} state=directory mode=2770

  - name: Creating {{ repo_name }} git repository
    command: git init --bare --shared /home/git/{{ repo_name }}

  - name: Updating repo permissions
    file: path=/home/git/{{ repo_name }} recurse=yes owner=git
Tags: [ ansible git ]
June 22, 2015

Server Move and Upgrades!

by Alpha01

My little corner of the internet has a new home. My old $29.99 8GB RAM, 3.40GHz Intel Core i3 dedicated server was simply not enough to handle my server needs. Which apparently OVH doesn’t even provide that service anymore. So instead I hoped to their mid-tear dedicated service service branch they call So you Start. I opted with their $49.00 SYS-IP-2 service. Now my server’s specs is a follows:

  • 2.66 GHz+ Intel Xeon W3520 (4 cores/ 8 threads)
  • 32 GB ECC
  • 2 x 2 TB SATA drives (Software RAID)

I would’ve love the drives to be SAS and the RAID to be hardware based, but it’s definitely not a deal breaker, and just $49.99 a month, it’s not much to complain about.

CentOS 6 to CentOS 7 upgrade

My server migration was fairly straight forward for the most part. I opted to re-create the KVM hypervisor and its guests from scratch. Mainly because I wanted to upgrade all of guests and host from CentOS 6 to CentOS 7. This is where I encountered my first problem. Since I rely on custom nat PREROUTING and POSTROUTING iptables firewall rules for my VMs to properly be able to talk to each other and to the internet. I realized CentOS 7 defaults to firewalld, so instead of trying to rewrite my firewall rules to be compatible with firewalld, I decided to continue to use CentOS 6 on my host operating system, and only upgrade my guests VMs to CentOS 7.

On a side note, my previous guest VMs were originally using raw image format (default cache settings) for its storage, and by god what a hell of a difference it makes changing to use native block storage via LVM. I/O performance on my old server was terrible, the I/O wait percentage was roughly about 6%, now it’s less than 1%. Even with the software raid, I/O performance is much better on my new server.

PHP 5.3 to 5.6 upgrade

Since I don’t have anything heavily customized on any of sites, the PHP version upgrade was practically painless.

Apache 2.2 to 2.4 upgrade

Luckily, upgrading Apache wasn’t a big hassle. Anyone considering upgrading from 2.2 to 2.4, it’s definitely worth checking out the official upgrade documentation since dropping the old 2.2 configs in onto a 2.4 environment won’t work off the gecko. In my case all of my sites were returning 403 forbidden replies and non of my .htaccess files weren’t being read by Apache. The fix was really simple.

<Directory /www/path-to-webroot>
    AllowOverride All
    Require all granted

I must say, I really like Apache 2.4 new authorization syntax. What used to be a three line configuration is now a single line configuration, and much more human readable.

Future Upgrade Plans

I didn’t tackle this during the server migration, but I’ll definitely going to be upgrading to Varnish 4 and use PHP FastCGI via php-fpm and mod_proxy_fcgi.

Tags: [ kvm php centos iptables apache ]
June 14, 2015

Networking Quirk in CentOS 7 - Virtual IP not being assigned

by Alpha01

I just realized the order of which the IP configurations are set in the /etc/sysconfig/networking-scripts/ifcfg-* file does matter. For example the following config was failing to assign the virtual IP on one of my systems:


Systemd was spitting out the following errors:

Jun 14 01:04:19 webapps network: RTNETLINK answers: File exists
Jun 14 01:04:19 webapps network: RTNETLINK answers: File exists
Jun 14 01:04:19 webapps network: RTNETLINK answers: File exists
Jun 14 01:04:19 webapps network: RTNETLINK answers: File exists


It turns out that the DEVICE and NAME declaration needs to be assigned and specified before the networking information.

Tags: [ centos networking ]