Linux

FAQs/HOW-TO's related to Linux and/or BSD server administration.

New Linux Server Checklist (2014 Edition)

These are some of the basic things I do when I setup a new server

 

Setup DirectAdmin with an SSL certificate

source: http://help.directadmin.com/item.php?id=15

If you don't own a certificate, you can create your own:

/usr/bin/openssl req -x509 -newkey rsa:2048 -keyout /usr/local/directadmin/conf/cakey.pem -out /usr/local/directadmin/conf/cacert.pem -days 9000 -nodes
chown diradmin:diradmin /usr/local/directadmin/conf/cakey.pem
chmod 400 /usr/local/directadmin/conf/cakey.pem

How to install a new drive in Linux larger than 2TB with proper alignment

Let's assume that we already have a primary physical drive in our system (HDD or SDD), and have added a second drive to our box, which we need to partition and mount automatically on boot.

Here's how to that:

Let's see what physical drives we have installed in our server:

ls /dev/sd*

Since this is our 2nd drive, you should see /dev/sdb.

Example:

How to fix Linux error "read-only file system"

Recently our /etc/fstab got screwed up preventing us from SSH-ing into the server after a reboot. So we were given KVM access to our server.

Once seting up Java to allow unsigned certificates--hint: under the Java Control Panel click the "Security" tab, and slide the "security level" to the bottom "Medium" . We were then greated with a message:

'give root password for maintenance or press ctrl+d to continue"

Come to find out CTRL-C and CTRL-V doesn't work, you have to type the pass by hand--this was very tedious since my root pass is extremely complex.

So once in I soon realized that the system was mounted as "read-only"; meaning that you couldn't make any changes to it; or in other words, completely useless at this state.

How to install CSF (ConfigServer Security & Firewall) with DirectAdmin

cd /usr/local/src
wget http://www.configserver.com/free/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh

Now login as Admin into directadmin, and click the link at the bottom left ConfigServer Firewall&Security

You'll probably want to add your WAN IP here--you can find out what it is here: http://www.ip-secrets.com/

Then add your WAN IP into Quick Allow column.

DirectAdmin how to set an external email server for Domain Pointers

If you ever created domain pointers in DirectAdmin, you may have wondered how to set the domain pointer NOT to process email locally.

For instance say you have PRIMARYDOMAIN.com as the main domain under your DirectAdmin account--and it is set NOT to process emails locally, but rather have an external email server handle that; Under MX Records you un-checked "Use this server to handle my emails. If not, change the MX record and uncheck this option". So now you decided to create a "domain pointer" under that same account for another domain SECONDARYDOMAIN.com ... You set the proper MX records for this domain pointer under DNS settings, pointing to the external mail server, and think you're all good to go...

How to prevent accidentally doing "rm -rf /" | How to Install safe-rm

As a server administrator, I rely mostly on root or sudo access--allowing me absolute control of the server. However, "with great power, comes great responsibility!"

You can easily accidentally do this devastatingly bad command of wiping your entire system clean.

rm -rf /
# or
rm -rf /*

Which looks almost identical to the popular command

How to upgrade coreutils to latest version (from source)

Say you're on CentOS 5.x, and want to pimp out your bash prompt using the pretty awesome Solarized color scheme. Well, there's a nice .bashrc Solarized setup here: https://github.com/seebi/dircolors-solarized. To use all the features of dircolors.256dark version, you'll need GNU coreutils 8.5 or higher, otherwise you'll get errors like this:

Enable Zend OPcache for PHP 5.5 or Install ZendOpcache for PHP 5.3 or PHP 5.4

Zend Opcache is part of PHP 5.5, however, it's not enabled by default. It's a successor to APC cache--meaning APC cache is never going to be compatible with PHP 5.5 or higher

Opcache is also around 10% faster than APC, and more stable.

However, if you're on PHP 5.3 or PHP 5.4, you can still use ZendOpCache, and it should still be a bit faster than APC

Enable OpCache (part of with PHP 5.5)

vi /usr/local/lib/php.ini

Paste this under your extension_dir

wget download all files from a directory with resume

Here is how you download all files from a directory using wget with automatic resume of partially downloaded files (in case your connection gets cut off)

wget -r -c --no-parent http://www.whateveraddress.com/downloads

Keep in mind this will only download files that it can read from that location.  If you need to wget a bunch of files from a directory you have SSH or FTP access to you first have to do the following inside that directory:

vi .htaccess

and paste in the following and save.

Categories: 

How to create a larger /tmp location using ext2 filesystem

Increasing the size of /tmp is not a practical thing to do on a busy server, mainly because you probably won't be able to dismount /tmp because it's constantly used by various services--trying to find and kill them all is too tedius. (Plus you won't be able to do single user mode through SSH)

So what we will do here is create a whole new /tmp storage location, make a backup of the old /tmp, add the new location to fstab, reboot the server, copy everything from the backup /tmpBKP location to new location, and lastly reboot the server again.

How to permanently raise ulimit 'open files' and MySQL 'open_files_limit'

The default ulimit (maximum) open files limit is: 1024--Which is very low, especially for a web server environment hosting multiple heavy database driven sites.

This ulimit 'open files' setting is also used by MySQL. MySQL automatically sets its open_files_limit to whatever the system's ulimit is set to--at default will be 1024.

NOTE: MySQL can NOT set it's open_files_limit to anything higher than what is specified under ulimit 'open files'--you can set it lower, but not above the 'open files' limit.

Anyhow...

This is how we raise the ulimit

To check the limits:

Categories: 

How to optimize and auto repair all MySQL databases using SSH

Here's a simple command to optimize and auto repair all tables in your MySQL database.

mysqlcheck -uroot -p --auto-repair --optimize --all-databases

This is the same thing as using PHPMyAdmin, however, you don't need to do this one by one for each database, select all tables, and optimize--and not to mention if you wanted to repair a database prior to optimizing, it will take 2x as long.

How to set date and time automatically in CentOS

tzselect

Answer the 3 locations questions. Then create a symlink to your local time.

rm -rf /etc/localtime
ln -sf /usr/share/zoneinfo/America/Los_Angeles /etc/localtime

The symlink will be according to your time zone--above is just an example.

Now, we check the date and time

date

Time and date should now be properly set.

Categories: 

How to install XCache 3.0 from source

Alright... So APC has been pretty unstable for me on 2 separate servers running PHP 5.3.x and PHP 5.4.x. So I figured I'd give XCache a try after reading about similar problems with APC.

Anyhow...

Here's how to install XCache 3.X from source on CentOS

Get the latest version of XCache from here: http://xcache.lighttpd.net/#Downloads

Latest version at the time of this writing is XCache 3.0.1

Drupal .htaccess rewrite with 'www' but not for sub-domains

Say you have your Drupal's .htaccess set "To redirect all users to access the site WITH the 'www.' prefix", and you added a sub-domain, and it came out looking something like http://www.sub.domain.com. So, most people will NOT want the "www" added to the url in this case. So what do you do? Easy.

Use this instead:

Categories: 

Add memcached Support to Magento

After you successfully install memcached and pecl/memcached (memcached PHP support), you will next want take full advantage of it by enabling native support for memcached in magento.

NOTE: you must have memcached and pecl/memcached already installed. Otherwise your Magento installation will break if you try following this guide.

Ok... now that the warning is out the way. Here's how we do it...

Edit your local.xml

vi ./app/etc/local.xml

Add the following between

How to set a custom sub-domain path in DirectAdmin

UPDATE: See below, there's an easier way to do this. Plus DirectAdmin's way doesn't seem to be working through the 'Custom HTTPD Configurations' way.... So, just use the way listed below. It's much easier.

*** OLD WAY / start ***
I work with Drupal's Domain Access module a lot. However, if you're using DirectAdmin as your hosting control panel, then making sub-domains will not work with the default setup. DirectAdmin puts the sub-domain into a separate directory, and in order for Domain Access to work with sub-domains on DirectAdmin, this needs to be set as the same directory/path as the top domain.

A simple work around is to login to DirectAdmin as administrator, and go into "Custom HTTPD Configurations".

Here you will paste the following code:

Cannot find autoconf. Please check your autoconf installation and the $PHP_AUTOCONF environment variable.

if you try running the following:

phpize

and get this error

$PHP_PREFIX/bin/phpize
Configuring for:
PHP Api Version: 20041225
Zend Module Api No: 20060613
Zend Extension Api No: 220060519
Cannot find autoconf. Please check your autoconf installation and the
$PHP_AUTOCONF environment variable. Then, rerun this script.

Then it's because you don't have autoconf installed.

To fix this error, do the following:

yum install autoconf

or you can install from source (if you want to use the latest version)


cd /usr/local/src/

/* find latest version of m4 here: http://ftp.gnu.org/gnu/m4/ */

Categories: 

phpMyAdmin database export "Save as file" template

Whenever you do a database backup using phpMyAdmin, you are presented with a default file name structure for saves, usually like so:

__DB__

which basically gives you the name of the database you just backed up. Which is ok, however, most people would also like the date and time stamp included as well...

So...

This is how it's done... replace the above with :

__DB__-%F-%T

or for newer version of phpMyAdmin

@DATABASE@-%F-%T

__DB__ = name of database Example: my_database
%F = Same as "%Y-%m-%d" (year-month-day) Example: 2009-11-25
%T = time stamp . (24 hour format, hour_minute_second) Example: 11_07_31

which will save a file with the naming structure similar to:

my_database-2009-11-25-11_07_31.sql

You can easily use other date/time structure, to suit your personal preference.

Categories: