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--- blocks:server:mirror [2020-05-21 08:32]
admin Minor edits
+++ blocks:server:mirror [2025-02-13 20:01] (current)
admin Added Sync Errors note
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 ====== Blocks Mirroring Service ======
-Our Linux-based Blocks server dated 2020-05-14 and later, running Ubuntu 20.04, supports a new redundancy feature for increased system reliability. While the Blocks server software is very robust, the complete system can never be more reliable than the hardware it runs on.
+Our Linux-based server supports a hardware redundancy feature for increased system reliability. While the Blocks server software is very robust, the complete system can never be more reliable than the hardware it runs on.
 ===== Introduction =====
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 Once you have configured your main Blocks Server as described above and have it all working as desired, it's time to make the Mirror Server by cloning the Blocks server. This is done using a program called Clonezilla. Read [[blocks:server:creating_a_server#prepare_clonezilla_usb_stick| this article]] on getting started with Clonezilla.
-You'll also need a second USB storage device. This may be a USB stick with enough room to store the actively used data from your Blocks server's disk. Or it may be an external USB disk drive. This storage device must be formatted as FAT32 to NTFS.
+You'll also need a second USB storage device. This may be a USB stick with enough room to store the actively used data from your Blocks server's disk. Or it may be an external USB disk drive. This storage device must be formatted as FAT32 or NTFS.
-Start by shutting down and re-booting your now fully configured Blocks server from a Clonezilla USB stick. This is done by selecting the USB stick as first boot device in the computer's BIOS, accessed by pressing a dedicated key on the keyboard during startup.
+Shut down and re-boot your now fully configured Blocks server from the Clonezilla USB stick. Select the USB stick as the boot device in the computer's BIOS, accessed by pressing a dedicated key on the keyboard during startup.
-Select English.
+Once Clonezilla has started, Select "English".
 {{:blocks:server:mirror:clone:language.png?nolink&500|}}
-Select your desired keyboard mapping.
+Select your keyboard layout, if you have a non-english keyboard, or just select "Keep the default".
 {{:blocks:server:mirror:clone:keyboard_settings.png?nolink&500|}}
-Start Clonezilla.
+Select "Start Clonezilla".
 {{:blocks:server:mirror:clone:startclonezilla.png?nolink&500|}}
@@ Line 161: / Line 161: @@
 {{:blocks:server:mirror:clone:localdevice.png?nolink&1000|}}
-Connect the //second// USB stick or external drive, that needs to be large enough to hold the used disk space from your Blocks server. Wait a few seconds as instructed, then press Enter.
+Connect the //second// USB stick or external drive. This drive must have enough free space to hold the used disk space from your Blocks server. Wait a few seconds as instructed, then press Enter.
 {{:blocks:server:mirror:clone:insertrepository.png?nolink&600|}}
-Once your newly connccted USB stick appears, press Ctrl-C to continue.
+Once your newly connccted drive appears, press Ctrl-C to continue.
 {{:blocks:server:mirror:clone:confirmstoragedeviceattached.png?nolink&1000|}}
-Select the newly connected USB device as your destination.
+Select the newly connected drive as your destination.
 {{:blocks:server:mirror:clone:mountdeviceimagerepository.png?nolink&1000|}}
-Click Done and press Enter to specify that the image is to be created at the root level of the USB stick.
+Click Done and press Enter to create the image at the root level of the drive.
 {{:blocks:server:mirror:clone:selectdirectory.png?nolink&1000|}}
@@ Line 185: / Line 185: @@
 {{:blocks:server:mirror:clone:selectwizard.png?nolink&600|}}
-Select the "savedisk" option to create an image from the servers internal disk.
+Select the "savedisk" option to create an image from the server's internal disk.
 {{:blocks:server:mirror:clone:savelocaldiskasimage.png?nolink&1000|}}
@@ Line 193: / Line 193: @@
 {{:blocks:server:mirror:clone:nameofimage.png?nolink&600|}}
-Select your source disk.
+Select your source disk (the internal disk of your Blocks server).
 {{:blocks:server:mirror:clone:selectsourcedisk.png?nolink&|}}
@@ Line 205: / Line 205: @@
 {{:blocks:server:mirror:clone:checkingsavedimage.png?nolink&|}}
-Select to "not encrypt the image".
+Choose to "not encrypt the image".
 {{:blocks:server:mirror:clone:encryptimage.png?nolink&|}}
@@ Line 217: / Line 217: @@
 {{:blocks:server:mirror:clone:entertocontiniue.png?nolink&1000|}}
-Verify the details then confirm by pressing y followed by Enter.
+Verify the details, then confirm by pressing y followed by Enter.
 {{:blocks:server:mirror:clone:confirm1.png?nolink&1000|}}
-Doublecheck the details then confirm by pressing y followed by Enter again.
+Double-check the details, then confirm by pressing y followed by Enter again.
 {{:blocks:server:mirror:clone:confirm2.png?nolink&1000|}}
-Wait for the cloning operation to conclude. This may take several minutes, depending on the amount of data on your source disk. Make sure the operation completes successfully.
+Wait for the cloning to conclude. This may take several minutes, depending on the amount of data on your source disk. Make sure the operation completes successfully.
 {{:blocks:server:mirror:clone:progresscaptureimage.png?nolink&600|}}
-The computer will shut down automatically once a clone has been made successfuly. Remove the USB sticks/drives. Restart your Blocks server and make sure it comes back OK. If it doesn't, re-enter its BIOS settings and set it back to start from its internal drive.
+The computer will shut down automatically once a clone has been made. Remove the USB sticks/drives. Restart your Blocks server and make sure it comes back OK. If it doesn't, re-enter its BIOS settings and set it back to start from its internal drive.
-[[blocks:server:creating_a_server#writing_the_server_image_to_the_ssd|This guide]] describes how to write the image to what will become your Mirror Server. You may want to store your clone image for safekeeping. It contains a snapshot of your Blocks server at this point in time, thus acting as a complete backup.
+[[blocks:server:creating_a_server#writing_the_server_image_to_the_ssd|This guide]] describes how to write the image to your Mirror Server, thus making it an exact copy of your Blocks server. Store your clone image for safekeeping. It contains a complete snapshot of your Blocks server at this point in time, thus acting as a full backup.
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   * Server Disk Space. Indicates the amount of free space on the Blocks Server itself. This also makes sens to keep an eye on – especially before adding a significant amount of new content.
   * Server Time. Shows the current time of the clock in the Blocks Server. If your server has Internet access, this is generally adjusted automatically. If not, you may want to check this every few monts to make sure that it is reasonably accurate.
+  * Sync Errors. Cumulative count of data sync errors that have occurred, if any. Check the Mirror log file for details.
-The SYNCHRONIZE NOW button can be used to force a full synchronization. Use this after making manual changes to the files in the /home/pixi-server directory of the Blocks server, such as updating Blocks itself or the mirroring service (the files PIXILAN.jar and MIRROR.jar respectvely). Doing so pushes those changes over to the Mirror Server immediately rather than waiting for the next scheduled full synchronization.
+The "Synchtronize Now" button can be used to force a full synchronization. Use this after making manual changes to the files in the /home/pixi-server directory of the Blocks server, such as updating Blocks itself or the mirroring service (the files PIXILAN.jar and MIRROR.jar respectvely). Doing so pushes those changes over to the Mirror Server immediately rather than waiting for the next scheduled full synchronization.
 ===== Testing the Mirror Server =====
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   * Set fullSyncOnStartup to //true// to run a full synchronization once when mirroring service is started.
   * Set java.util.logging.FileHandler.level to //ERROR// for less verbose logging, or //INFO// for more details (sometimes useful when troubleshooting).
+The following additional, advanced settings are available in version 7.1 and later, then specified under the "mirror:" heading as shown above.
+<code>
+  interface: enp2s0
+  subnet: 192.168.0.0/24
+</code>
+:!: **NOTE**: There are two spaces at the beginning of each line, as required when used under the "mirror:" heading.
+  * The //interface// setting is useful if your computer have more than one network interface with link local addressing. If so, use this setting to specify the name of the desired synchronization backdoor network interface.
+  * The //subnet// setting lets you specify a non link local subnet (in CIDR notation) for use as the data synchronization backdoor. This is useful in cases where you may want to use this interface for other purposes, such as remote management of the servers. You would then either set fixed addresses (within the specified subnet) or use dynamically assigned addresses (DHCP).
 The settings under //logging// follow the java.util.logging standard, sometimes referred to as JUL, allowing you to use any settings available there, for example to log to an external log handler.
+=====Troubleshooting=====
+Unless the advanced //subnet// setting is used (see above), the server-to-server backdoor connection assumes the use of self-assigned ("link local") addresses. Such adresses are in the 169.254.x.x address range. There must not be any additional network interfaces in either computer having such IP addresses. If there are, do either of the following:
+  * Disable any such interface(s). in some cases this may need to be done in the computer's BIOS settings.
+  * Change their addresses to keep them out of this address range.
+  * Use the advanced //nic// setting to specify which interface to use.
+=== Verifying over SSH ===
+The mirroring service shows its status window while running, as described above. If you're accessing your server using a terminal session over SSH, you can instead use this command to ascertain whether the mirroring service is running, while being logged in as the pixi-server user:
+<code>
+systemctl --user status blocks.mirror
+</code>
+=====Implementation Notes=====
+These notes provide additional understanding of how the mirroring service works. While not generally something you need to know, these details may be of assistans in some installations or when troubleshooting a system.
+===Synchronized files===
+The following directories and files are synchronized:
+  * /home/pixi-server/PIXILAB-BLOCKS-root/*
+  * /home/pixi-server/native/*
+  * /home/pixi-server/*.sh (e.g., the command-line start and stop scripts)
+  * /home/pixi-server/PIXILAN.jar (the Blocks software)
+  * /home/pixi-server/MIRROR.jar (the Mirroring software)
+  * /home/pixi-server/PIXILAB-Blocks-config.yml (if it exists)
+:!: **NOTE:** Any additional files you want to synchronize, such as SSL certificates, must be placed inside the PIXILAB-BLOCKS-root
+===Starting/stopping Blocks===
+The Linux [[https://en.wikipedia.org/wiki/Systemd|systemd]] feature is used to start and manage most programs that aren't started manually. This includes Blocks as well as the Mirroring service. You can see how this is done inside the start.sh and stop.sh scripts located in the home directory of the pixi-server user. When //not// using the mirroring service, //systemd// directly starts and manages Blocks.
+However, when using the mirroring service, //systemd// starts the mirroring service (referred to by the name //blocks.mirror//). Then, when appropriate (i.e., when the license key is connected) the mirroring service starts Blocks. Likewise, if the license key is disconnected (e.g., to be moved to the other server), the mirroring service shuts down Blocks. Here, //systemd// isn't directly responsible for starting/stopping Blocks. Therefore, viewing its //systemd// status (e.g. using the //systemctl --user status blocks// command) will show its status as inactive, even though it's running. Other system commands can be used to look at running processes.
+The mirroring service also generates its own log, found in the logs directory inside your Blocks root directory. Check these log files if you encounter any problems related to the mirroring service.