Ruby on Rails

Most frequently asked questions

1. How to connect to MySQL (Web interface & CLI)

   Web Interface

   
   

   Adminer is a database management web applicarion

   
   

   URL : https://12.34.56.789:12322
   Username: adminer
   Password : 

   
   

   Command line

   
   

   MySQL command line tool log in as root (no password required):

   
   

   $ mysql --user root 
   Welcome to the MySQL monitor. Commands end with ; or \g. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. 
   mysql>

2. How to connect to Cloud Application shell (Web interface & CLI)

   Web based command line

   
   

   URL :  https://12.34.56.789:12320/
   User : root

   
   

   SSH

   
   

   Login as root.

   
   

    

   
   

   From Windows you can access your server using a free simple SSH client program called Putty located at our Downloads.

   
   

   From Linux :

   
   

   ssh root@12.34.56.789

   
   

   * Replace 12.34.56.789 with a valid IP or hostname.

   
   

    

   
   

    

   
   

    

3. Hot to connect to System control panel (Webmin)

   System control panel

   
   

   Point your browser to:  https://12.34.56.789:12321/

   
   

   Username : root
   Password : 

   
   

   * Replace 12.34.56.789 with a valid IP or hostname.

   
   

    

4. What is Reverse DNS?

   Reverse DNS (rDNS) is name resolution that looks up an IP addresses to obtain a domain name, performing the opposite function of the DNS server, which turns domain names into IP addresses.

   
   

   Reverse DNS can be used as a spam filter. Typically, spammers use invalid IP addresses, that is, ones that do not match domain names. A reverse DNS program looks up the IP address of an incoming message and, if no valid domain name is found, the server blocks the message. Although reverse DNS is fairly effective for filtering spam, it also often blocks valid emails.

   
   

   Our administrators configure reverse DNS on all of our email servers. If you administrate your own server, you can contact your IP address's provider to configure reverse DNS.

5. Tune MySQL / mariadb database for WooCommerce and WordPress

   WooCommerce can really give mysql or mariadb a pounding.

   
   

   On smaller hosting platforms WooCommerce will grind to a halt.

   
   

   If you have a VPS, here are a few things you can tune, to give you fast database performance. The faster the database goes, the faster WooCommerce goes:

   
   

    

   
   

   InnoDb cache

   
   

   Assuming of course that you’re using innodb (which is a must – see below)

   
   

   innodb_buffer_pool_size=1024M

   
   

   The size should be as large as your wp_postmeta and wp_options tables, or 50% or more of your WooCommerce database. Don’t go above 25% of the RAM in your VPS.

   
   

    

   
   

   Query Cache

   
   

   There are a few articles out there saying disable query cache , but I think it really helps the WordPress wp_options table, which WooCommerce stores most of its data in.

   
   

   query_cache_limit=2M

   
   

   query_cache_size=64M

   
   

   query_cache_type=1

   
   

   If you have a lot more memory in your VPS, try this:

   
   

   query_cache_limit=8M

   
   

   query_cache_size=256M

   
   

   query_cache_type=1

   
   

    

   
   

   Make sure you’re using innodb

   
   

   Innodb is the fastest and most reliable database engine for mysql , mariadb, WordPress and WooCommerce. Here’s how to check.

   
   

   
   
   • Login to PHPMyAdmin
   
   
   • Select the database for your WP site.
   
   
   • Click the SQL tab.
   
   
   • Type this:   show table status
   
   
   • Click GO.
   
   

   
   

   You are looking for engine and you want InnoDB.

   
   

   If it’s myisam you need to fix it. Use this command in PHPMyAdmin (as above). make sure you have a good backup first.

   
   

   
   
   • ALTER TABLE tablename ENGINE = InnoDB
   
   
   • you’ll need to it for each table that was myisam  (replace tablename with each table)
   
   

6. Resize an LVM volume

   Logical Volume Management (AKA LVM) is a powerful, robust mechanism for managing storage space.

   
   

   In TurnKey 11,  instead of installing the root filesystem directly to a fixed size partition, we setup LVM by default, and install the root filesystem to a Logical Volume, which may later be expanded, even across multiple physical devices.

   
   

   Unfortunately, as with anything powerful, to get the most out of LVM you first have to negotiate a learning curve. From the feedback we've been getting it seems that confusion regarding LVM is  common with new users, so here's a quick "crash course"...

   
   

   How LVM works

   
   

   In LVM, there are several layers, each builds on top of the other:

   
   

   PV[s] (Physical Volumes) -> VG[s] (Volume Groups) -> LV[s] (Logical Volumes) -> Filesystems.

   
   

   Logical Volumes are allocated/extended within the boundaries of their underlying storage pool which is called a Volume Group in LVM terminology.

   
   

   For example, in TurnKey the filesystem is installed by default to the /dev/turnkey/root Logical Volume, which is allocated within the turnkey Volume Group:

   
   

   --- Logical volume ---
   
     LV Name                /dev/turnkey/root
   
     VG Name                turnkey
   
     LV UUID                OzX3fe-aRQa-81XM-0vCV-8aJo-eUL4-6J90XJ
   
     LV Write Access        read/write
   
     LV Status              available
   
     # open                 1
   
     LV Size                17.0 GiB
   
     Current LE             4502
   
     Segments               2
   
     Allocation             inherit
   
     Read ahead sectors     auto
   
     - currently set to     256
   
     Block device           251:0
   
   

   
   

   Out of the box the turnkey Volume Group doesn't have too much free space:

   
   

   # vgdisplay
   
     --- Volume group ---
   
     VG Name               turnkey
   
     System ID
   
     Format                lvm2
   
     Metadata Areas        1
   
     Metadata Sequence No  3
   
     VG Access             read/write
   
     VG Status             resizable
   
     MAX LV                0
   
     Cur LV                2
   
     Open LV               2
   
     Max PV                0
   
     Cur PV                1
   
     Act PV                1
   
     VG Size               18.14 GiB
   
     PE Size               4.00 MiB
   
     Total PE              4645
   
     Alloc PE / Size       4480 / 17.50 GiB
   
     Free  PE / Size       165 / 660.00 MiB
   
     VG UUID               IwaFL0-QCi8-iIUE-TWjQ-R906-PYpH-gMPaH9
   
   

   
   

   We can only extend a Logical Volume within the free space of the underlying Volume Group. How much free space we currently have within the Volume Group can be seen in this part of the output:

   
   

   Free  PE / Size       165 / 660.00 MiB
   
   

   
   

   In the above example we only have 660 MB to allocate to LVMs within the turnkey Volume Group. So if we want to extend the root LV we'll have to first extend the VG backs it up.

   
   

   Volume Groups group together Physical Volumes. That's why they're called Volume Groups. This command will show us which Physical Volumes have been registered into LVM, and to which volume groups they have been assigned:

   
   

   # pvdisplay
   
     --- Physical volume ---
   
     PV Name               /dev/sda2
   
     VG Name               turnkey
   
     PV Size               18.15 GiB / not usable 4.00 MiB
   
     Allocatable           yes
   
     PE Size               4.00 MiB
   
     Total PE              4645
   
     Free PE               165
   
     Allocated PE          4480
   
     PV UUID               H1Prpv-0VXR-7moE-zsbt-eyVt-m0fQ-GkAT6w
   
   

   
   

   In this example we only have one Physical Volume (the /dev/sda2 partition) in the turnkey Volume Group.

   
   

   Extending a Logical Volume

   
   

   Bottom line: if the underlying Volume Group doesn't have enough free space, to extend the Logical Volume you'll first have to extend the underlying Volume Group by adding another Physical Volume to it.

   
   

   In VMWare you could either create a new virtual hard disk device to add to the volume group, or extend an existing virtual hard disk device, create a new partition with cfdisk, and add the new partition to the Volume Group:

   
   

   # example #1: you've added to VMWare a new virtual hard disk called /dev/sdb
   
   pvcreate /dev/sdb
   
   vgextend turnkey /dev/sdb
   
   
   
   # example #2: you've expanded the existing sda hard disk
   
   cfdisk /dev/sda  # creating /dev/sda3 (you may need to reboot before you can see this)
   
   pvcreate /dev/sda3
   
   vgextend turnkey /dev/sda3
   
   

   
   

   After you've extended the Volume Group, you are free to extend the underlying Logical Volume:

   
   

   # lvextend -L+10G /dev/turnkey/root
   
   Extending logical volume root to 27.0 GiB
   
   Logical volume root successfully resized
   
   

   
   

   Finally, you'll have to resize the filesystem within /dev/turnkey/root so it can see that the underlying block device just got 10G bigger:

   
   

   # resize2fs /dev/turnkey/root
   
   resize2fs 1.41.11 (14-Mar-2010)
   
   Filesystem at /dev/turnkey/root is mounted on /; on-line resizing required
   
   old desc_blocks = 2, new_desc_blocks = 2
   
   Performing an on-line resize of /dev/turnkey/root to  7077888 (4k) blocks.
   
   The filesystem on /dev/turnkey/root is now 7077888 blocks long.

7. How to extend an EXT4 partition using parted and resize2fs

   Firstly, we want to extend the partition using parted:
   
   

   
   

   
   

   Bash:

   
   

   
   

   root@cana:~# parted /dev/sda
   
   GNU Parted 3.2
   
   Using /dev/sda
   
   Welcome to GNU Parted! Type 'help' to view a list of commands.
   
   (parted) resizepart 1                                                  
   
   Warning: Partition /dev/sda1 is being used. Are you sure you want to continue?
   
   Yes/No? Yes                                                            
   
   End?  [275GB]? -0                                                      
   
   (parted) quit                                                          
   
   Information: You may need to update /etc/fstab.
   
   
   
   root@cana:~#

   
   

   
   

   
   

   
   Hint:

   
   

   
   
   • resizepart 1 to resize /dev/sda1
   
   
   • -0 resizes it to the end of the disk. - Indicates that it should count from the end of the disk, not the start. This makes -0 the last sector of the disk - which is suitable when you want to make it as big as possible.
   
   

   
   

   
   If we type df -H it will still showing the old size:

   
   

   
   

   Bash:

   
   

   
   

   root@cana:~# df -H
   
   Filesystem      Size  Used Avail Use% Mounted on
   
   /dev/sda1       271G  240G   18G  94% /
   
   udev             11M     0   11M   0% /dev
   
   tmpfs           1.3G  8.8M  1.3G   1% /run
   
   tmpfs           3.2G   25k  3.2G   1% /dev/shm
   
   tmpfs           5.3M     0  5.3M   0% /run/lock
   
   tmpfs           3.2G     0  3.2G   0% /sys/fs/cgroup
   
   root@cana:~#

   
   

   
   

   
   

   
   Secondly, we need to use resize2fs to extend the volume:
   (The file system meta information needs to indicate the size of the disk, and resize2fs updates this.)
   
   

   
   

   
   

   Bash:

   
   

   
   

   root@cana:~# resize2fs /dev/sda1
   
   resize2fs 1.42.12 (29-Aug-2014)
   
   Filesystem at /dev/sda1 is mounted on /; on-line resizing required
   
   old_desc_blocks = 16, new_desc_blocks = 29
   
   The filesystem on /dev/sda1 is now 117964544 (4k) blocks long.
   
   
   
   root@cana:~#

   
   

   
   

8. Connecting using PuTTY on Windows workstations

   Configuring PuTTY
   
   

   
   

   
   
   1. In PuTTY, under Session, enter your Host Name
      
      
      
      
      
   
   
   2. Under Connection choose Data
   
   
   3. Enter your username as the Auto-login username
      
      
      
      
   
   
   4. Under SSH, choose 2 from Preferred SSH Protocol Version
   
   
   5. Under SSH -> Auth, you will need to specify where your private key can be found. Remember this is where you saved the private key on your local computer. Click Browse to locate the file on your computer.
      
      
      
      
   
   
   6. Under Sessions, type a name (such as "my site") in the Saved Sessions box and click Save.
   
   

9. Connecting using SSH on Linux or OSX workstations

   Use the ssh command to connect to your instance. Specify your username and the external IP address for the instance that you want to connect to.

   
   

   Download Prive Key from client area and save it to your workstation
   
   For this example, the private key is at ~/.ssh/my-ssh-key.
   
   ssh -i ~/.ssh/my-ssh-key USERNAME@IP_ADDRESS

   
   

   where:

   
   

   
   
   • USERNAME is your username
   
   
   • IP_ADDRESS is the IP for your Cloud Server.
   
   

   
   

   If the connection is successful, you can use the terminal to run commands on your instance.

   
   

   When you are done, use the exit command to disconnect from the instance.

10. How to create a .ppk from private key on Windows

    Using a Public/Private key to authenticate when logging into SSH can provide added convenience or added security. The Public/Private key can be used in place of a password so that no username/password is required to connect to the server via SSH. Instead the unique public and private key provide the secure authentication. The keys may also be generated with a different password from your cpanel password if desired.
    
    

    
    

    Generate a ppk file
    
    

    
    

    
    
    1. Download and open PuTTYgen here.
    
    
    2. Click Load
       
       
       
       
       
    
    
    3. Locate the private SSH key that you have downloaded. Note: You will need choose to display All Files* from the menu to the right of the File Name field. 
    
    
    4. Click the Save private key button to create the ppk file.
       
       
    
    

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