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Category Misc

Hetzner server with > 2TB disk

Recently I ordered a Hetzner server for one of our clients. The server had two 3TB disks. Hetzner provides a command line installation of the desired OS once we login to their server. As such, I logged in to the server and installed Centos6 by executing “installimage” option as suggested by Hetzner.

After installing OS and rebooting the server, I noticed that the 3T disk is not showing full space.

[root@abc ~]#df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        99G  2.5G   91G   3% /
tmpfs           463M     0  463M   0% /dev/shm
/dev/sda2       976M  126M  800M  14% /boot

/dev/sda4   2.3T     123M   2.2T  1% /home

If the disk size is greater than 2T you cannot use normal fdisk to create partition...

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Fatal error: Class ‘Net_SMTP’ not found in /usr/local/lib/php/Mail/smtp.php on line 349″

I was trying to setup a php script to send mail with SMTP Authentication. The script was ready, but when executed in a browser, it displayed the following error.

Fatal error: Class ‘Net_SMTP’ not found in /usr/local/lib/php/Mail/smtp.php on line 349″

The problem appears because the php pear package Net_SMTP is not present in the server. You can install it in two way.

  1. Install the Mail package with –alldeps which will install all required dependencies like Net_SMTP

pear install –alldeps Mail

If Mail is already installed, and if it refuses to get installed then you can force the installation as follows.

pear install –alldeps -f Mail

2.  If Mail is already installed, then you can install the Net_SMTP option alone as follows.

pear install Net_SMTP

After that, execute the script again and...

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df showing wrong result

My mysql server suddenly started showing my disk space usage as almost full.

[root@abc /]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3       550G  508G   14G  98% /
tmpfs            32G     0   32G   0% /dev/shm
/dev/sda1       2.0G  173M  1.8G   9% /tmp

But when I issued a disk usage check on / , it returned the usage to be very little.

[root@abc /]# du -sch
47G     .
47G     total

I was sure there is something wrong. Hence, I checked for deleted files. You can use either of the following commands.

[root@abc /]# lsof +L1

mysqld    23193     mysql    5u   REG    8,1          184     0       13 /tmp/ibrUf6yr (deleted)
mysqld    23193     mysql    6u   REG    8,1            0     ...

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(28)No space left on device: mod_rewrite: Parent could not create RewriteLock file

Noticed this error in a cpanel server while starting apache. Apache refused to start with the following error.

(28)No space left on device: mod_rewrite: Parent could not create RewriteLock file

Seeing the error, the first thing that I checked was the disk space in the server but it looked fine.

root@abc [~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg0-root   16G  1.2G   14G   8% /
/dev/mapper/vg0-home  249G  124G  113G  53% /home
/dev/mapper/vg0-var    23G  7.0G   15G  33% /var
/dev/mapper/vg0-usr    23G  7.6G   14G  36% /usr
/dev/mapper/vg0-tmp   9.5G  151M  8.9G   2% /tmp
/dev/sda1             7.4G  184M  6.9G   3% /boot
tmpfs                 7.9G     0  7...

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Accessing Gmail with Roundcube

Requirement : I want to access my gmail under my own domain with the help of webmail.

Say my domain name is abc.com , I want to access it as http://abc.com/mail

Suppose I am on a cpanel server. Download and install Roundcube as follows.

root@me [/home/abc/public_html]# wget http://downloads.sourceforge.net/project/roundcubemail/roundcubemail/1.0.0/roundcubemail-1.0.0.tar.gz

root@me [/home/abc/public_html]# tar -xzvf roundcubemail-1.0.0.tar.gz

root@me [/home/abc/public_html]# mv roundcubemail-1.0.0 mail

root@me [/home/abc/public_html]# chown -R abc:abc mail

root@me [/home/abc/public_html]# cd mail

Now login to your cpanel and create a database for roundcube installation, create a database user and assign privileges. This can all be done from cpanel.

Once done, go to the installer link as ...

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Migrating emails from mailenable to exim

I wanted to transfer my entire sites from my Windows Plesk server to Linux Cpanel server. I could simply create the new accounts in the new server and copy the files. The main issue was with emails. My windows server was using mail enable, where as the the cpanel server uses exim.

I realized I will have to create all email accounts manually in the new server. A simple tool which will do everything in a click was not available. Losing email was not something I could let happen, so I decided to go ahead with creating accounts and then copying emails. I used imapcopy for it. If anybody wants to do it, you can do it as follows. I am copying the email account test@abc.com to new server. Its password is test123c on both servers.

root@abc [~]# cd /usr/local/src/

root@abc [/usr/local/src]#  wget ...

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Sharding in MongoDB

Sharding refers to the process of distributing data across multiple servers which helps in retrieving it easily. When the data set is huge, it is said that sharding significantly improves the query response time.

Let us see how we can implement sharding. Sharding requires a  minimum of three servers for test purpose. In production scenario, sharding may require more servers.

Sharding is implemented through the following :-

1) Config Servers – These servers contain the metadata as to where the data belongs to. Means, it holds data as to which shard each data goes. A minimum of 2 config servers in a huge databases system is recommended.

2) Query Router Servers – These servers are the ones that communicate with the application directly...

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Find the number of FTP connections along with the connected IP Addresses

You can use the following t o find which all IP Addresses are connected to server via FTP as well as the number of connections.

netstat -tpn | grep pure-ftpd | awk ‘{print $5}’ | cut -d”:” -f1 | sort | uniq -c | sort -nr

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ERROR: Error creating index db.collection-101613_nno.csv: 16633 err: “text search not enabled”

I was trying to restore a database onto a new server, when I got the following error.

mongorestore -d db /backup/db

ERROR: Error creating index db.collection-101613_nno.csv: 16633 err: “text search not enabled”

In order to correct this, you need to enabled text search. Simply stop the mongo process and start it with text search enabled.

root@abc# /etc/rc.d/init.d/mongod stop

root@abc# /usr/bin/mongod -f /etc/mongod.conf –setParameter textSearchEnabled=true

Now try restoring again and it works.

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Configuring SSL in nginx

Suppose you have a domain greproot.com for which you want to enable SSL. Make sure you have a dedicated IP for the domain. Say, is the dedicated IP address for greproot.com

First, decide where you want to keep your certs and keys. In my case, I am going to place it in /etc/ssl/certs/ and /etc/ssl/keys respectively.

[root@abc ~]#mkdir /etc/ssl/certs/

[root@abc ~]#mkdir /etc/ssl/keys

Now we need to generate CSR and key for the greproot.com, get the cert signed and then install SSL.

[root@abc ~]#cd /etc/ssl/keys

[root@abc ~]#openssl genrsa -out greproot.com.key 2048

[root@abc ~]# chmod 600 greproot.com.key

[root@abc ~]# cd /etc/ssl/certs/

[root@abc ~]#openssl req -new -key greproot.com.key -out greproot.com.csr

Now we have the CSR and key...

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