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More detail still needs to be added

Most of the time Unraid systems function with minimal problems. This section is intended to help with resolving issues that are most commonly encountered.

There are some important general guidelines that it is recommended that a user follows that will help with any troubleshooting that may be required:

  • Use the built-in Help: The Unraid GUI has extensive built-in Help for most fields in the GUI. This can be accessed at the individual field level by clicking on the field name, or toggled on/off for the whole page by clicking on the Help icon at the top right of the GUI.
  • Use the online documentation: There is extensive online documentation that can be accessed via the Manual link at the bottom of the Unraid webGUI.
  • Enable Notifications: Unraid has a notification system that can be used to keep you informed about the health of your Unraid system. This can be enabled and the level of notifications you receive tuned under Settings->User Preferences->Notification Settings. Since Unraid systems often function for very long times without needing any user oversight it can be important that you are informed of problems when they first occur as if left unresolved they can grow into more serious ones.
  • Proactively fix any reported issues:
  • Ask for help in the forums: Unraid has a vibrant user community and many knowledgeable users who are active in the Unraid forums. Any time you encounter a problem and you are not sure how to proceed it is a good idea to ask questions in the forums. There is nothing worse than rushing into trying to fix a problem using a process you do not understand and as a result making a problem that was initially easy to resolve into something more serious
  • Capture diagnostics: If you want to ask a question in the forums about a problem you are encountering you are frequently going to be asked to provide your system diagnostics file. You need to do so BEFORE YOU REBOOT so that the logs show went wrong BEFORE the reboot (because once you reboot, it's lost)!

Capturing Diagnostic Information

When you encounter any sort of problem it is always recommended that you attempt to capture as much information as possible to help with pinpointing the cause. If you want to ask questions in the forum such information will typically be requested as it will speed up the process of getting meaningful and accurate feedback.

System Diagnostics

Unraid has a GUI option under Tools->Diagnostics to capture a lot of information about the state of your system that can be helpful when trying to diagnose any issues. Using this tool will result in a zip file being produced that can be downloaded and then attached to forum posts.

If the GUI cannot be accessed, then use SSH, telnet, or a keyboard/monitor attached to the server to login and type diagnostics. This will save the file to the "logs" folder on your flash drive.

The Diagnostics should if at all possible cover the period when the problem occurred and be captured BEFORE you reboot (logs are reset on a reboot) so that the logs show what happened leading up to the problem occurring. The zip file produced can then be attached to a forum post when asking for help on a problem in the Unraid forums. It is preferred that you attach them to a new post if you have already started a thread on your issue so that other forum users are notified that there has been something added to the thread.

These system diagnostics include configuration information, state information, and key system logs. When creating the diagnostics from the GUI then details of the sort of information that will be included are listed. There is an option (set by default) to say that the diagnostics should be anonymized to try and avoid including any information that might be deemed sensitive.

All the files in the diagnostics are text files so a user is free to examine them to check for themselves exactly what information is present.

In most cases it is preferable that the diagnostics are captured after the array has been started in Normal mode as this gives the maximum information about the state of your Unraid system, in particular if any drives are having any problems. There will be times, however, when this is not possible, or you will be advised to capture the diagnostics in a different state as a result of feedback in a forum thread. It is still better to have some level of diagnostics rather than nothing.

IMPORTANT: The diagnostics are a single zip file containing multiple files. If it seems to you that the diagnostics is a lot of files and folders, it is because your computer automatically opens zip files. Do not upload all those files individually to a forum post but instead find that single diagnostics zip file in your downloads and attach that single diagnostics zip file to your NEXT post in the relevant forum thread.

Note on anonymization of the diagnostics

It has been pointed out that the diagnostics are not completely anonymized if you have enabled mover logging under Settings->Mover Settings as the syslog will give details of files that mover is operating on. This is a bit of a catch-22 scenario as when one has enabled mover logging it is normally to investigate a problem where as much detail as possible is captured so attempting to anonymize such information may well be counter-productive. Since mover logging is disabled by default and recommended practice is to only have it enabled when investigating why mover is not giving the expected results this is probably acceptable.

Persistent Logs (Syslog server)

The main system log is the syslog file and it is the contents of this file that is displayed when you click the icon at the top right of the Unraid GUI. Note that when posting to the forums extracted fragments of the syslog are rarely helpful as they do not show what lead up to a problem occurring.

Normally the logs are only written to RAM so do not survive the system being rebooted. If you are investigating a system crash then as long as you are running Unraid 6.7.2 or later there is built-in syslog server support

  • Go to Settings->Network Services->Syslog Server

  • You can click on the 'Help' icon on the Toolbar and get more information for all of the options.

Mirror to Flash: This is the simplest to set up. You select

'Yes' from the dropdown box and click on the 'Apply' button and the syslog will be mirrored to the logs folder/directory of the flash drive and is appended to on a reboot. There is one principal disadvantage to this method. If the condition, that you are trying to troubleshoot, takes days to weeks to occur, it can do a lot of writes to the flash drive. Some folks are hesitant to use the flash drive in this manner as it may shorten the life of the flash drive.

  • The advantage of this approach is that it captures everything from the start of the boot process which can be important if trying to diagnose boot problems.

Remote Syslog Server: This is used when you have another machine

on your network that is acting as a syslog server. This can be another Unraid server. You can also use virtually any other computer. You find the necessary software by googling for the syslog server of that computer's operating system. After you have set up the computer/server, you fill in the computer/server name or the IP address. (I prefer to use the IP address as there is never any confusion about what it is.) Then click on the 'Apply' button and your syslog will be mirrored to the other computer.

  • The other computer has to be left on continuously until the problem occurs.
  • The events captured will only start with the point at which the syslog daemon is started during the boot process thus missing the very start of the boot process.

Local Syslog Server: Set this to Enabled to setup this

Unraid server to act as a network syslog server. When this is enabled then some extra options are offered. The built-in Help gives guidance /n suitable settings.

  • Local syslog folder: This will be a share on your server but chose it with care. Ideally, it will be a 'cache only' or a 'cache preferred' share. This will minimize the spinning up of disks due to the continuous writing of new lines to the syslog. A cache SSD drive would be the ideal choice here using a cache preferred share. The syslog will be in the root of that folder/share.

  • Local syslog rotation: These settings allow you to control how much space the syslog is allowed to use.

    • Local syslog maximum file size:
    • Local syslog number of files:
  • If you click the 'Apply button at this point, you will have this server setup to serve as a Remote Syslog Server. It can now capture syslogs from several computers if the need should arise.

Logging to file local to Unraid server Using a bit of trickery

we can use the Unraid server with the problem as the Local syslog server. This is appropriate if you want to continue to keep a permanent copy of the syslog but the file will not be as easy to access if the Unraid system is crashing. It also has the advantage of avoiding lots of writes to the flash drive. To achieve this you now add the IP address of this server as the Remote syslog server (Remember the mention of trickery). So basically, you send data out-of-the-server and it comes-right-back-in.


  • The standard system diagnostics include the RAM copy of the syslog so there is no need to provide this separately. You will need to do so to provide the logs captured by the syslog server as these are not included in the standard system diagnostics.

Docker Containers

The standard system diagnostics do not contain much that will help with diagnosing issues with specific docker containers.



The standard system diagnostics do not contain much that will help with diagnosing issues with specific VMs.


Boot Issues

Preparing the flash drive

This is covered under the Getting Started section of the documentation.

If for any reason you decide that you need to redo the flash drive then it is a good idea to make sure you first backup the current flash drive (or have a recent backup) as all user specific settings (including the licence key) are held in the config folder on the flash drive. Copying the config folder (and all its contents) back to the flash drive after redoing it will preserve all current settings.

Enabling UEFI boot

You get asked if you want UEFI mode boot support when using initially creating the flash drive. However it is always possible to enable UEFI mode booting at a later stage by renaming the folder on the flash drive called efi~ to efi (i.e. removing the trailing ~ character).

Boot Process

Most of the time the Unraid boot process runs seamlessly and the user needs no awareness of the various stages involved. However, when things go wrong it can be useful to know how far the boot process managed to get as this will be of use in knowing what remedial action to take.

Resolving boot issues will typically need either a locally attached monitor+keyboard or (if the motherboard supports it) an IPMI connection to carry out equivalent functionality. This can then be used to set any required BIOS stings and to monitor the booting process.

The boot process for Unraid proceeds through a number of stages

  1. Bios boot: This is the stage at which the motherboard BIOS recognizes the presence of the Unraid bootable flash drive

    • The way that the Unraid flash drive is set as the default boot device is BIOS dependent so you may need to consult your motherboard's User Manual to determine the correct way to do this.
    • The Unraid flash drive supports booting in Legacy mode (also sometimes known as CSM mode) for older BiOS's and UEFI for more recent ones. Many recent BIOS's support both modes.
    • If you want UEFI boot mode to be used then the EFI folder on the flash drive must not have trailing tilde (~) character.
  2. Syslinux loader

    Boot Menu

    • The entries that appear on the boot menu are specified by the syslinux/syslinux.cfg file on the flash drive. Although in theory this file can be edited manually as it a text file it is recommended that it is done via the GUI by clicking on the flash drive on the Main tab and going to the Syslinux configuration section
    • The Memtest86+ option only works if booting in Legacy mode. If booting in UEFI mode it will typically simply cause a reboot. If you want a version that will work in UEFI boot mode then you need to download it for yourself from either or
    • If the user does not select a specific option then after a timeout period the default option will be used. If Unraid is running in headless mode this is the option that will be run.
  3. Linux core: This is the stage at which the syslinux boot loader takes over from the BIOS and starts loading the files specified in the syslinux.cfg file.

    • This is when the core Linux system is loaded from the flash drive and unpacked into RAM.
    • There will be messages on the console about the various bz* types being loaded into RAM.
    • If there are any error messages displayed while loading these files then it normally indicates a problem with the flash drive.
    • There will then be messages displayed as Linux starts up and detects the hardware environment.
  4. Flash dependent services: At this stage, the flash drive is mounted at /boot so that the process can continue

    • If the mount of the flash fails it is still possible to get the login prompt displayed. However, this does not necessarily mean the whole boot process completed correctly.

    • If this stage of the boot process has not completed then typical symptoms are that the webGUI and network are not started

    • One way to see if this has happened is to login and use the df command. If the flash drive was mounted successfully then you will see it as /boot in the resulting list of mount points.

      • The output should have something like following mount points:
      • /dev/sdb1 15413232 826976 14586256 6% /boot
        /dev/loop0 9344 9344 0 100% /lib/modules
        /dev/loop1 7424 7424 0 100% /lib/firmware
    • One reason the flash drive may fail to mount is that it is not labelled as UNRAID (all capitals).

    • Additional drivers and firmware are now available on the above mount points.

    • Configuration information is read into RAM from the flash drive.

    • Standard Linux services are started. Examples would be networking and (if enabled) WireGuard VPN.

  5. Plugins

    • If the user has installed plugins then they are normally loaded at this stage.
    • If one of the Safe Boot options was selected from the Unraid Boot menu then the loading of plugins is suppressed.
  6. Web GUI

    • The Unraid web GUI is started.
    • The webGUI is actually done via an entry in the config/go file on the flash drive so it is possible for user-supplied commands to also be run from there either before starting the webGUI or just after doing so.
  7. Array

    If the user has set the array to be auto-mounted then the following will start. If array auto-start is not set then they happen when the user elects to start the array.

    • Drives mounted

      Mount points will now be created of the form /dev/diskX and /mnt/cache (if you have a cache).

    • File Share Services

      Shares will now become available on the network.

      At the Linux level the shares will now appear as paths like /mnt/user/sharename

    • Docker Containers

      If the user has enabled the docker services then the Docker containers will be started using the order on the Docker tab.

      The order of the containers and delays between starting the containers can be set on the Docker tab.

    • VMs

      Any VMs the user has set to auto-start will now be started

By this stage, the Unraid server will be fully operational.

Boot Failures

The following are some actions that can be taken to try and pin down the cause of a boot failure:

  1. if possible use a USB2 port in preference to a USB3 one as they seem to be more reliable for booting purposes. In addition USB2 drives also seem less prone to failure than USB3 ones. Many modern motherboards no longer have USB2 ports directly exposed but there is normally a USB2 header on the motherboard that can be used via an appropriate adapter.
    • USB3 does work with no problems for many people
    • After initial load Unraid runs from RAM so gains no significant performance advantage from using USB3.
    • USB2 drives tend to run cooler than USB3 ones which probably explains why they tend to last longer.
    • USB2 drives are typically cheaper than USB3 ones- so why pay more if not needed
  2. Check that the BIOS on the Unraid server still has the flash drive set as the boot device. It has been known to get reset for no obvious reason.
  3. On a windows 10 PC or a Mac run a check on the flash drive
    • This will determine if something is wrong physically or logically with the flash drive
    • If you do not already have one make sure you have a copy of the config folder of the flash drive as this contains all your current configuration information.
  4. Download the zip version of the release from Limetech and extract all the bz* type files over-writing those on the flash drive
    • This will determine if these files were not written correctly for some reason or are corrupt.
  5. Rewrite the flash drive with a clean copy of Unraid and copy across just the key file from your backup to the config folder
    • This can determine if the flash drive itself is OK
    • Copy across the remaining contents of the config folder to the flash drive
      • If this goes well you are back up and running with your previous configuration intact.
      • If this fails then try booting in Safe Mode. If this works then a plugin is causing problems
  6. If the original flash drive cannot be made to boot try a brand new flash drive and clean copy of Unraid (with the default configs)
    • This can determine if something is wrong with the server's hardware (mobo, cpu, ram, usb port, etc.)
  7. Install a clean/new copy of Unraid on a new flash drive and then copy the config folder over from the old one.
    • If this works then the licence will need to be transferred to this new flash drive.

Lost root Password

Occasionally users lose their password for managing Unraid via the Unraid webGUI or console. This may be that they simply forgot the password, but corruption of the flash drive can also result in the password not being recognized.

Passwords for shares can be changed/reset from the Unraid webGUI.

To reset the management password use the following process:

  1. Shutdown server and then plug the USB boot flash device into a PC or Mac

  2. While there it is a good idea to run a check on the flash drive and make a backup of its contents

  3. Delete these files:

    • config/passwd
    • config/shadow
    • config/smbpasswd
  4. Plug the flash back into the server and start up again.

Note that this will reset all user passwords including 'root' user to null (blank).

There is an alternative procedure that can be used for just resetting the root password (but is a little more prone to error):

  1. Plug the USB drive into another computer

  2. Bing up an editor (such as Notepad++) on the following file:

    • /boot/config/shadow
  3. On the first line you should see something such as:


  4. Change that line to the following (essentially delete the content between the first and second colons):


  5. Plug flash back into server and start up again.

Lost boot drive and do not know which are the parity drives

Occasionally users get the scenario where they have the following combination of circumstances:

  • Unraid boot drive has failed
  • There is no recent backup of the boot drive that can be used to restore the drive configuration
  • There is uncertainty about which drives are the parity drives.

The issue is how to get the Unraid system operational again on a new boot drive without data loss. You can exploit the fact that Unraid will recognise any data disk previously used by Unraid as containing a valid file system compatible with Unraid, and that the parity drives do not contain a valid file system

The basic approach is:

  • Create a new Unraid boot drive.
  • Boot the Unraid server off this new drive. At this point no drives will be assigned.
  • Get the new drive licenced. This can be using either a trial licence or by following the procedure for transferring an existing licence to a new boot drive.
  • Identify which drives are the parity drives. There are 2 ways to do this as shown below.
  • Use Tools -> New Config to reset the array. It is normally easiest to use the option to retain previous assignments but this is not mandatory.
  • Return to the main tab and now that you know which are the array disks and which are the parity disk(s) correct the assignments to reflect this. You can (optionally) re-order the data drives at this point but be aware this will always invalidate parity2
  • Start the array to commit the drive assignments. If you have used an approach that has not invalidated parity you can now tick the "Parity is Already Valid" checkbox to avoid rebuilding parity. If in doubt do not tick this checkbox.
  • Make any corrections that assume a specific array drive order. For instance If you had any includes/excludes set for a User Share you may want to check them against the current assignments and correct if needed.
  • If you did not rebuild parity you may well want to run a parity check at this point to ensure that parity really was valid. If you used method 2) below to identify the parity drives then there will be at least a small number of parity errors so you should run a correcting check as soon as possible.

Identifying the parity Drives

There are two slightly different approaches that can be used to identify the parity drives. If you get unexpected results then you should ask for help in the forums before proceeding.

1) Using the Unassigned Devices plugin

This approach uses a 3rd party plugin. It has the advantage that it will not automatically invalidate parity drives.

The process is:

  • Install the Unassigned Devices plugin via the Apps tab if you have not already done so.
  • Mount all the disks read-only in turn. You need to use the Read-only mode to avoid any changes to the drive that will invalidate parity.
  • Any disk that will not mount should be a parity drive (although you cannot tell if it is parity1 or parity2 if you have dual parity).
  • While the drive is mounted you might want to look quickly at the contents if the order of the data drives matters to you to see if you can identify the order for the data drives

2) Using Unraid built-in capability

This approach does not need to use a 3rd party plugin and will invalidate parity so that it need so be rebuilt.

The process is:

  • Assign ALL data drives to the array and start the array. Unraid will recognise any drives that have previously been used by Unraid and leave their contents intact

  • At this point any parity drives will show as unmountable since the parity drives contain no file system. You should have the same number of unmountable drives as you had parity drives and as long as this is the case make a note of their serial numbers. If this is not the case ask for help in the Unraid forums on the best way to proceed.

  • While the drives are mounted you might want to look quickly at the contents if the order of the data drives matters to you to see if you can identify the order for the data drives.

Backing Up Boot Drive

Since the Unraid boot drive contains all user specific settings in the 'config' folder You should ideally always make a backup of the Unraid boot drive any time you make any significant configuration changes.

There are various ways of achieving this:

  • From the Unraid GUI via Main -> Boot -> Device -> Flash -> Flash Backup. This will create a zip file that you then download.
  • by Installing Unraid Connect, which provides for automated backups to cloud servers managed by Limetech.
  • by plugging the flash drive into a PC/Mac and copying the full contents to a local folder on the PC/Mac

Manually Upgrading (or Downgrading) an Unraid release

Follow the same process as laid out in the section below for handling bzimage checksum errors.

Bzimage checksum error/failure reading flash drive

Sometimes when booting you get a message displayed on a locally attached monitor indicating that something has gone wrong when trying to load the Unraid OS files into RAM from the flash drive. There are two typical manifestations of this

  • An explicit message stating that a read error has occurred
  • A message stating that there is a checksum failure on a bz* type file (most commonly bzimage). This most commonly happens after updating the Unraid OS (which is one time a lot of data is written to the flash drive in one go), although it can happen at any time.

Note: This procedure can also be used to upgrade or downgrade an Unraid release

The normal recovery action is:

  • Plug the flash drive into a PC/Mac and make sure it is able to read the flash drive (and let it repair any corruption it finds). If the flash drive cannot be read then this indicates the flash drive had probably failed and you need to follow the procedure for transferring your settings to a new flash drive.
  • (optional) Make a backup of the flash drive. Although not strictly necessary at this point it is always a good idea to have an up-to-date backup of the flash drive. All your settings are in the config folder on the flash drive and this procedure leaves that unchanged.
  • Download the zip file for the release. The last few Stable releases will have the download link on the Download page on the Unraid web site. Every forum page will have a Download link at the top right to take you to that page. For beta/rc test releases you can normally get the link by asking in the Bug reports->Preleases section of the Unraid forums.
  • Extract all the bz* type files from the zip file and overwrite the corresponding files on the flash drive.
  • Extract the changes.txt file and overwrite the one on the flash to ensure you have one that corresponds to the bz* type files you have just placed on the flash drive. The system will work if you do not copy this file but it is good practice to keep it in sync with the release that is currently active.
  • Tidily eject the flash drive from the PC/Mac.
  • Boot the Unraid server of the freshly written flash drive.

If the above does not help then it is advisable to post in the Unraid forums stating what you have tried and what are your current symptoms.

Unclean Shutdowns

Sometimes on booting up the system and starting the array a parity check is automatically started due to an Unclean Shutdown. An Unclean shutdown occurs when Unraid thinks that the array was not successfully stopped when the system was last powered off. This can be caused by a wide variety of issues:

  • The most obvious cause is unexpected power loss. The best protection against this type of issue is to have an Uninterruptible Power Supply (UPS) that is set up to initiate a controlled shutdown of Unraid initiated by the UPS when the amount of power left in the UPS reaches a trigger level.
  • The status of the array is stored on the flash drive, so if for any reason the status on the flash drive cannot be updated due to the flash drive either dropping offline or going into read-only state for some reason then Unraid will not be able to update this status even if the array is stopped successfully.
  • Another common reason for an unclean shutdown is having a terminal session open.  Unraid will not force them to shut down, but instead waits for them to be terminated while the shutdown timer is running.  After the overall shutdown timer runs out, the server is forced to shutdown.  If you have the Tips and Tweaks plugin installed, you can specify that any bash or ssh sessions be terminated so Unraid can be gracefully shutdown and won't hang waiting for them to terminate (which they won't without human intervention).

There are various timeouts that are started when a shutdown of the array is started that run in parallel and many users find the defaults are too low for their particular workload:

  • There is a timer in the Settings->VM Manager->VM Shutdown (in advanced view) that needs to be set to a high enough value to allow your VMs time to completely shutdown.   Windows VMs will sometimes have an update that requires a shutdown to perform.  These can take quite a while and the default setting of 60 seconds in the VM Manager is not long enough.  If the VM Manager timer setting is exceeded on a shutdown, your VMs will be forced to shutdown.  This is just like pulling the plug on a PC. A reasonable value is something like 300 seconds (5 minutes) in order to insure your Windows 10 VMs have time to completely shutdown.
  • There is a timer for stopping Docker Containers under Settings -> Docker (in advanced view). If this timeout is reached then docker containers still running will be Force Stopped.
  • If you have remote SMB or NFS mounts in Unassigned Devices you need to account for time for them to time out if the remote server has gone off-line when unmounting.  You should allow something like 45 seconds for each remote mount.  They are unmounted sequentially, so you need to account for 45 seconds for each one.
  • There is an final timer used for shutdowns under the Settings->Disk Settings->Shutdown time-out.  This is the overall shutdown timer and when this timer is exceeded, an unclean shutdown will occur.  This timer has to be more than the VM and docker shutdown timers.  A reasonable value might be something like 420 seconds (7 minutes) to give the system time to completely shut down all VMs, Dockers, and plugins.

It can be useful to use the Stop option on the Main tab with your normal workload running and time how long it takes. The overall shutdown timer should be set to at least this value plus a small extra margin to allow for variability.

If you server seems hung and nothing responds, try a quick press of the power button.  This will initiate a shutdown that will attempt a graceful shutdown of the server.  If you have to hold the power button to do a hard power off, you will get an unclean shutdown.

If an unclean shutdown does occur because the overall "Shutdown time-out" was exceeded, Unraid will attempt to write diagnostics to the /log folder on the flash drive.  When you ask for help in the Unraid forums with an unclean shutdown, post the /log/ file.  There is information in the log that shows why the unclean shutdown occurred.

It can also be good idea to activate the Settings->Syslog Server to get logs that can survive a reboot as by default the syslog is only in RAM and lost after a reboot.

Crash Issues


RAM Issues

It is known that RAM degrades over time. RAM issues can be elusive to track down and cause unpredictable errors. A somewhat common effect is unexpected file system level corruption.

The Unraid boot menu includes a version of memtest for testing RAM. This version will only work if booting in Legacy mode. If you try to run this when running in UEFI mode it will immediately reboot again.

If you want a version that can be used in UEFI mode then you can download a newer version from memtest's website. Note that the version of memtest built into Unraid is a much older version that doesn't have the newer testing capabilities of the current version located on memtest's website. This is no fault of Unraid, the people behind memtest won't allow anything newer to be installed by 3rd parties.

Over-clocking RAM

Many people want to run their RAM at the maximum rated speed quoted in the specification of the RAM they have purchased. They tend to forget that many motherboard/CPU combinations have a max speed at which they can reliably drive RAM regardless of the fact that the RAM may be rated for a higher theoretical maximum clock rate.

Windows Connection Issues


The majority of users have no problem making connections to Unraid shares. Having said that Microsoft is continually tweaking the network security model via Windows Update and this can cause problems for some users.

If you encounter problems then your first port of call should probably be the Windows issues with Unraid forum thread. This thread is rather long so you probably want to start near the end.


Name Resolution

Stored Credentials

Multiple Sign-ons

Data Recovery


A lot more detail still needs to be added

This section is about recovering your data when Unraid reports problems with one or more drives.

There are some important points to bear in mind about securing your data

  • Backup critical data: Unraid will protect you against most types of simple hardware failure, but not catastrophic failure. You should ALWAYS have backups of any critical data that you cannot afford to lose. Ideally one of those copies should be offsite or on the cloud to protect yourself against unforeseen issues such as fire, theft, flood, etc.
    • Each user has to make their own determination of what they deem critical and make an assessment of the level of risk they are prepared to take.
    • Personal data such as photographs & documents tend to always be deemed critical. Luckily these tend to be relatively small so easy to back up.
    • Media files are often deemed non-critical and are relatively large so a user may well decide these do not merit being backed up
    • Personal video that can never be replaced should fall into the critical category regardless of its size
    • Remember that there are things such as ransomware around so there should be at least one copy of critical files that cannot be accessed online and corrupted if you are unfortunate enough to suffer from such an attack!
  • Be proactive about resolving any issues that are detected by Unraid. Make sure that notifications are enabled under Settings->Notifications so that you get told as soon as issues are detected. For many users, Unraid operates in a fire-and-forget mode so that they will not be actively checking for problems so need such reminders.
  • Ask for Advice:
    • The Unraid forums have lots of knowledgeable users who can help guide you through what needs doing to get your data back into a standard if you are not sure what are the best steps to take.
    • Unraid is very good about protecting your data against typical hardware failures, but it is not immune to users taking inappropriate steps to recover their data after a failure occurs.

Unmountable Disk(s)

If a disk that was previously mounting fine suddenly starts showing as unmountable then this normally means that there is some sort of corruption at the file system level. This most commonly occurs after an unclean shutdown but could happen any time a write to a drive fails or if the drive ends up being marked as 'disabled' (i.e. with a red ',' in the Unraid GUI).

IMPORTANT: At this point, the Unraid GUI will be offering an option to format unmountable drives. This will erase all content on the drive and update parity to reflect this making recovering the data impossible/very difficult so do NOT do this unless you are happy to lose the contents of the drive.

The correct way to proceed in such a case is to follow the procedure for checking and repairing the file system. The vast majority of the time this will repair the disk that was previously showing as unmountable and now it will mount correctly and all your data will be intact. If you are not sure how to proceed then ask a question in the Unraid forums.

Lost Array Configuration

If you have lost the array configuration and do not have a current backup of the flash drive the data will still be intact on the drives.

All configuration information is stored on the flash drive in the config folder. In particular, the Unraid array configuration is stored in the config/super.dat file.

  • Do not attempt to use an out-of-date backup that may have incorrect drive assignments.

If you know which drives were the parity drives then you can simply reassign the drives. However, if you do not know which were the parity drives then you have to be more careful as incorrectly assigning a drive to parity that is really a data drive will result in you losing its contents.

When you do not know which were your parity drives the following steps can get your array back into operation:

  1. Assign all drives as data drives
  2. Start the array
  3. All the genuine data drives should show as mounted and the parity drive(s) show as unmountable. If this is not the case and too many drives show as unmountable then stop and ask for help in the forums giving details of what happened.
  4. Make a note of the serial numbers of the parity drives.
  5. Stop the array
  6. Go to Tools->New Config. Select the option to retain current assignments (as it reduces the chance of error). Click the yes I want to do this and then Apply.
  7. Go back to the Main tab and correct the assignments of the parity drives. Double-check you have the right drives now assigned as parity drives as assigning a data drive to parity will lose its contents. You can move any other drives around at this stage as well.
  8. Start the array and the system will start building parity based on the current assignments.

All your User Shares will re-appear (as they are simply the aggregation of the top-level folders on each drive) but with default settings, so you may need to re-apply any customization you want.

You can now go configure any other customization that is appropriate and add any plugins you normally use.

At this point, it is strongly recommended that you click on the flash drive on the Main tab and select the option to download a backup of the flash drive. It is always good practice to do this any time you make a significant change.

Using ddrescue to recover data from a failing disk

In normal use, a tailed/disabled disk is recovered under Unraid using the Replacing Disks procedure.

Occasionally it can happen due to a variety of reasons, like a disk failing while parity is invalid or two disks failing with single parity, a user having a failing disk with pending sectors and no way to rebuild it using parity, the normal Unraid recovery processes cannot be used. In such a case you can try using ddrescue to salvage as much data as possible.

To install ddrescue install the Nerd Pack plugin then go to Settings -> Nerd Pack and install ddrescue.

You need an extra disk (same size or larger than the failing disk) to clone the old disk to, using the console/SSH type:

ddrescue -f /dev/sdX /dev/sdY /boot/ddrescue.log

Both source and destination disks can't be mounted, replace X with source disk, Y with destination disk, always triple-check these, if the wrong disk is used as destination it will be overwritten deleting all data.

It's also possible to use an array disk as the destination, though only if it's the same size as the original, but to maintain parity you can only clone the partition, so the existing array disk needs to be a formatted Unraid disk already in any filesystem, still to maintain parity you need to use the md# device and the array needs to be started in maintenance mode, i.e., not accessible during the copy, by using the command:

ddrescue -f /dev/sdX1 /dev/md# /boot/ddrescue.log

Replace X with source disk (note the 1 in the source disk identifier), # with destination disk number. It is recommend to enable turbo write first or it will take much longer.

Example output during the 1st pass:

GNU ddrescue 1.22
ipos:  926889 MB, non-trimmed:    1695 kB,  current rate:  95092 kB/s
opos:  926889 MB, non-scraped:        0 B,  average rate:  79236 kB/s
non-tried:    1074 GB,  bad-sector:        0 B,    error rate:       0 B/s
rescued:  925804 MB,   bad areas:        0,        run time:  3h 14m 44s
pct rescued:   46.28%, read errors:       54,  remaining time:      3h 18m
time since last successful read:          0s
Copying non-tried blocks... Pass 1 (forwards)

After copying all the good blocks ddrescue will retry the bad blocks, forwards and backwards, this last part can take some time depending on how bad the disk is, example:

GNU ddrescue 1.22
ipos:   17878 MB, non-trimmed:        0 B,  current rate:       0 B/s
opos:   17878 MB, non-scraped:   362496 B,  average rate:  74898 kB/s
non-tried:        0 B,  bad-sector:    93696 B,    error rate:     102 B/s
rescued:    2000 GB,   bad areas:      101,        run time:  7h 25m  8s
pct rescued:   99.99%, read errors:      260,  remaining time:         25m
time since last successful read:         10s
Scraping failed blocks... (forwards)

After the clone is complete you can mount the destination disk manually or using for example the UD plugin (if the cloned disk is unmountable run the appropriate filesystem repair tool, it might also be a good idea to run a filesystem check even if it mounts OK) and copy the recovered data to the array. Some files will likely be corrupt and if you have checksums or are using BTRFS you can easily find out which ones. If not see below.

If you don't have checksums for your files (or use btrfs) there's a way you can still check which files were affected:

Create a temporary text file with a text string not present on your data, e.g.:

printf "Unraid " >~/fill.txt

Then fill the bad blocks on the destination disk with that string:

ddrescue -f --fill=- ~/fill.txt /dev/sdY /boot/ddrescue.log

Replace Y with the cloned disk (not the original) and use the existing ddrescue mapfile.

Finally mount the disk, manually or for example using the UD plugin and search for that string:

find /mnt/path/to/disk -type f -exec grep -l "Unraid" '{}' ';'

Replace /path/to/disk with the correct mount point, all files containing the string "Unraid" will be output and those are your corrupt files, this will take some time as all files on the disks will be scanned, the output is only displayed in the end, and if there's no output then the bad sectors were in areas without any files.



A lot more detail still needs to be added

Docker Image Full

Unraid expects docker containers to be configured so that only the binaries for the container are held in the docker.img file. All locations within the container that write variable data are then expected to be mapped to locations external to the docker.img file.

The default size of 20GB is enough for all but the most demanding users so if you find that your docker.img file is running out of space it definitely sounds as if you have at least one container incorrectly configured so it is writing internally to the docker image rather than to storage external to the image.

Common mistakes are:

  • Leaving off the leading / on the container side of a path mapping so it is relative rather than absolute
  • Case mismatch on either side of a path mapping as Linux pathnames are case-significant.

If you cannot spot the error then you can try:

  • Go to the docker tab and click the Container size button. often this will highlight the problem docker container(s) so you now know where to look.

If that is not enough to identify the culprit then:

  • Make sure all containers are stopped and not set to auto-start
  • Stop docker service
  • delete current docker image and set a more reasonable size (e.g. 20G)
  • Start docker service
  • Use Apps->Previous apps to re-install your containers (with all their settings intact).
  • Go to docker tab and click the Container size button

: This will give you a starting point for the space each container is using.

  • Enable one container, let it run for a short while, and then press the Container size button again to see if that particular container is consuming space when it runs.
  • Repeat the above step until you track down the rogue container(s)

How do I move docker.img?

The normal reason for wanting to move the docker.img file is because it has ended up on a drive that is not the one you want it to use.

Note: In many cases it is easier to just recreate the docker.img file from scratch rather than to try and move it.

The way to move docker.img is:

  • Go to Settings -> Docker -> Enable Docker, and set to No, then click the Apply button  (this disables Docker support). This is required because othewise the Docker service will keep this file open which stops you from moving it elsewhere.
  • Using mv or any file manager or the command line, move docker.img to the desired location (/mnt/cache/docker.img is recommended)
  • In Settings -> Docker, change the path for docker.img to the exact location you just copied to
  • Set Enable Docker back to Yes, and click the Apply button again  (re-enabling Docker support)

How do I recreate docker.img?

The commonest reason for wanting to recreate the docker.img file is because it has been corrupted. This is typically indicated by seeing error messages in the syslog relating to the loop2 device (which is the mount point for the docker.img file).

Other common reasons for recreating the docker.img file is because you want to change the amount of space that you have allocated to it or to change its location.

  • Go to Settings -> Docker -> Enable Docker, and set to No, then click the Apply button  (this disables Docker support)
  • Switch to Advanced View, then check off the box and press Delete
  • Make sure that the settings for the size and location are what you want them to be.
  • Now set Enable Docker back to Yes, and click the Apply button again  (re-enabling Docker support) and a new empty docker.img file will be created.

Restoring your Docker Applications

It is very easy to reinstall the binaries for all your Docker containers and get back your containers with their settings intact if you have installed them via Community Applications.

  • Go to the Apps Tab
  • Select the Previous Apps Section.
  • Check off all of your previous applications that you want to be reinstalled and hit Install.

This will download the binaries for all of your Docker containers into the docker.img file and reinstate them with their settings intact.

Further Information

A wealth of further information and some common problems with docker (and the solutions) can be found in the Docker FAQ on the forum


Users frequently see that they are getting UDMA CRC errors (SMART attribute 199) reported for some drives.

A CRC error indicates that the drive has noted that it has not correctly received the data from the host, and typically indicates a connection issue of some sort. This will normally trigger Unraid to attempt a recovery by resending the data. If this resend succeeds then Unraid will continue as normal, but the retry will have the end effect of slowing down the perceived write speed due to the delay caused by the retry. These retry attempts will show up as entries in the syslog.

If the recovery attempt fails then after several retries Unraid will decide it has a Read error on the drive. If the array is parity protected this will then trigger Unraid to attempt to rewrite the problem sector with the correct data based on the parity data and the corresponding sector on all the 'good' data drives. If this write succeeds then Unraid will continue as normal, but if the write fails Unraid will disable the drive and stop using it. This disabled state is indicated in the GUI by the fact that the drive is flagged with a red 'x'.

Possible causes of such errors are:

  • Badly seated SATA cables. The SATA connector is not a very robust connector and can easily work slightly loose due to vibration or tension on the cables. It is also a good idea to avoid 'bundling' the cables together in an attempt to tidy up the cabling as this can result in cross-talk interference between the cables.
  • Bad SATA cables.
  • Insufficient power to the drive. Quite frequently associated with splitter cables on the power lines, but also possible if the power supply is insufficient to power all drives simultaneously so that power dips occur.
  • Badly seated disk controller
  • Genuine disk problem (least likely but not unknown).

The first guidance that is always given in the forum when a user reports CRC errors is to first carefully check the SATA and Power cabling to the drives as this is by far the commonest cause of such issues.

Points to note are:

  • Occasional CRC errors are not really a cause for concern but if they are happening regularly or in large numbers then this definitely needs looking into to determine the cause and fix the issue.
  • It is not unusual for the Current pending sector count (SMART attribute ) 197 to also be incremented when getting a lot of CRC errors. This is more of a cause for concern as it means these sectors may not be read reliably if another disk fails and a recovery action needs to be performed as error-free recovery requires all 'non-failed' drives to be read without error.
  • The CRC count is stored internally in the drive's SMART information and never resets to zero - it can only ever increase.
  • A CRC error will result in the Dashboard page indicating a SMART related issue has happened by an orange 'thumbs-down' symbol against the drive.
  • The user can acknowledge they have seen such an error by clicking on the orange symbol and choosing the 'Acknowledge' option from the resulting menu that is displayed. This will result in the icon turning green again and Unraid will only prompt you again if the value of the CRC count increases.

Cache/Pool issues

Mover is not moving files

The commonest cause for this is simply new users misunderstanding the Use Cache setting for a share and getting the Yes and Prefer settings back-to-front. If you want files to initially be written to the cache and later moved to the array then you ned to use the Yes setting and not the Prefer setting.

Another common mis-conception is that changing the Use Cache setting to Only or No will trigger mover to transfer files to/from their current location to match the new Use Cache setting. In fact mover takes no action on shares that have this setting so the files are left in their current location.

Another point is not realizing that the Docker and VM services keep certain files permanently open (particularly in the system, domains, and appdata shares) and this can stop mover acting on those files. It is not enough to simply stop all running containers and/or VMs - you actually need to disable the services themselves to allow such files to be moved.

###Files end up on a pool (cache) despite Use Cache=No setting for a share

This behaviour is the one that new users find most perplexing.

It arises when a 'move' action is attempted at the Linux level. (This can be either from the command line or within a container (since all container are Linux based).) It arises from the fact that Linux is not aware of User Shares combined with the way that Linux implements a 'move' operation. If Linux thinks that both source and target are on the same mount point (and all User Shares are under the /mnt/user mount point) then it first tries a rename command and for speed and only if that fails does it revert to trying a copy + delete operation. In the case of a cache/pool this 'rename' succeeds so the file is left on the same drive but under a new folder name corresponding to the target share name. Since User Shares are simply an amalgamated view of the top level folders on all drives this means that suddenly the file(s) in question can end up on a drive that has the Use Cache=No setting. Since mover ignores shares with the Use Cache setting of No or Only this will result in the files being left stranded on a pool that the target share has not been configured to use for caching purposes.

*This behaviour can also occur if you try and move files between two User Shares that are set to use different Pools for caching purposes.* Once again this can result in the files ending up on the wrong pool.

Workarounds to this issue are by doing any of the following:

  • Manually move the file(s) in question to the drive where you want it to be finally located.
  • Set the share that the file has ended up in to have the Use Cache=Yes setting and then when mover runs the file will get transferred to the array following the rules for that share to pick the array drive. You can either start mover manually from the Main tab or wait until it runs automatically at its next scheduled time. Once mover has been run you can either leave the Use Cache setting as Yes or change it to the setting you want to use long term.
  • Do an explicit copy + delete operation.
  • Do the move over the network as at the network level two different User Share will never appear to be on the same mount point so a copy + delete is done automatically.
  • Make sure the mount points for source and target appear to be different at the Linux level.
  • Move between physical drives rather than at the User Share level.