docs/doc/source/system_configuration/kubernetes/customize-crashdumpmanager-46e0d32891a0.rst

Customize Crash-dump-manager

The Linux kernel can be configured to perform a crash dump and reboot in response to specific serious events. A crash dump event produces a crash dump report with bundle of files that represent the state of the kernel at the time of the event, which is useful for post-event root cause analysis.

The kernel directs the new crash dump bundles to /var/crash/<dated dump bundle>. Crash dump bundles are quite large and they can fill up their target filesystem.

The purpose of crash-dump-manager service is to prevent crash dumps from filling up the root filesystem by compressing the crash bundles found in /var/crash and moving it to /var/log/crash. The first bundle is compressed as vmcore_first.tar and preserved. Subsequent crash bundles are saved as vmcore_<date>.tar.

The status of the crash-dump-manager can be checked by running the following command:

% sudo systemctl status crash-dump-manager
  crash-dump-manager.service - Crash Dump Manager
     Loaded: loaded (/lib/systemd/system/crash-dump-manager.service; enabled; vendor preset: enabled)
     Active: inactive (dead) since Mon 2023-09-18 23:08:10 UTC; 14s ago
   Main PID: 1328880 (code=exited, status=0/SUCCESS)
        CPU: 22ms

Change the Default Crash-dump-manager Configuration

The crash-dump-manager service uses four parameters in order to customize its behavior. You can change the parameter values using service-parameters. The editable parameters and their default values are as follows:

Maximum Files

Number of saved crash dump files in crash dump file system (/var/log/crash). Default: 4

Maximum Size

Limits the maximum size of an individual crash dump file. Support for unlimited. Default: 5GiB

Maximum Used

Limits the maximum storage used by saved crash dump files. Support for unlimited. Default: Unlimited

Minimum Available

Limits the minimum available storage on the crash dump file system. Default: 10% of crash dump file system size Minimum: 1GiB

Configuration Parameters Units

When configuring the Maximum Size, Maximum Used, and Minimum Available parameters, you have the flexibility to specify the units of measurement. These parameters accept integer/float values followed by the unit of measurement, that can be written in two primary forms: units based on the metric system (decimal) and units based on the binary system (binary prefixes).

• Decimal units (metric system)

  K: Represents kilobytes, where 1 KB is equal to 1,000 bytes.

  M: Represents megabytes, where 1 MB is equal to 1,000,000 bytes.

  G: Represents gigabytes, where 1 GB is equal to 1,000,000,000 bytes.

  T: Represents terabytes, where 1 TB is equal to 1,000,000,000,000 bytes.

  Example:

  5K represents 5 kilobytes (1 KB = 1,000 bytes).

  5M represents 5 megabytes (1 MB = 1,000,000 bytes).

  5G represents 5 gigabytes (1 GB = 1,000,000,000 bytes).

  5T represents 5 terabytes (1 TB = 1,000,000,000,000 bytes).

• Binary units (binary prefixes)

  Ki: Represents kibibytes, where 1 KiB is equal to 1,024 bytes.

  Mi: Represents mebibytes, where 1 MiB is equal to 1,048,576 bytes.

  Gi: Represents gibibytes, where 1 GiB is equal to 1,073,741,824 bytes.

  Ti: Represents tebibytes, where 1 TiB is equal to 1,099,511,627,776 bytes.

  Example:

  5Ki represents 5 kibibytes (1 KiB = 1,024 bytes).

  5Mi represents 5 mebibytes (1 MiB = 1,048,576 bytes).

  5Gi represents 5 gibibytes (1 GiB = 1,073,741,824 bytes).

  5Ti represents 5 tebibytes (1 TiB = 1,099,511,627,776 bytes).

• Unlimited

  Additionally, the Maximum Size and Maximum Used parameters support the special value unlimited. When the parameter value is set to unlimited, there are no imposed restrictions on the size or storage usage.

Ensure that you have sufficient storage available on the host’s log filesystem. For more information about adjusting the storage size, see resizing-filesystems-on-a-host.

1. Add a crash dump service parameter.

   ~(keystone_admin)]$ system service-parameter-add platform crash dump <parameter>=<value>

2. Modify an existing crash dump service parameter.

   ~(keystone_admin)]$ system service-parameter-modify platform crashdump <parameter>=<value>

3. Delete an existing crash dump service parameter.

   ~(keystone_admin)]$ system service-parameter-delete <uuid>

   Note

   When a parameter is deleted, its value will be reset to the default value.

Where, <parameter> can be one of these: max_files, max_size, max_used, min_available.

Example:

The following example adds Maximum Files, Maximum Size, Maximum Used, and Minimum Available.

[sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-add platform crashdump max_files=6

+-------------+--------------------------------------+
| Property    | Value                                |
+-------------+--------------------------------------+
| uuid        | 3f5d8bc0-26cc-43b5-aeb6-d6a5b5b27035 |
| service     | platform                             |
| section     | crashdump                            |
| name        | max_files                            |
| value       | 6                                    |
| personality | None                                 |
| resource    | None                                 |
+-------------+--------------------------------------+

[sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-add platform crashdump max_size=unlimited
+-------------+--------------------------------------+
| Property    | Value                                |
+-------------+--------------------------------------+
| uuid        | 164b5630-9125-4482-b08d-5b5b80d25e14 |
| service     | platform                             |
| section     | crashdump                            |
| name        | max_size                             |
| value       | unlimited                            |
| personality | None                                 |
| resource    | None                                 |
+-------------+--------------------------------------+

[sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-add platform crashdump max_used=10G
+-------------+--------------------------------------+
| Property    | Value                                |
+-------------+--------------------------------------+
| uuid        | f2a6d3b4-0b9f-40d9-89b1-4e06d425cf79 |
| service     | platform                             |
| section     | crashdump                            |
| name        | max_used                             |
| value       | 10G                                  |
| personality | None                                 |
| resource    | None                                 |
+-------------+--------------------------------------+

[sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-add platform crashdump min_available=4,5Gi
+-------------+--------------------------------------+
| Property    | Value                                |
+-------------+--------------------------------------+
| uuid        | da4af8a9-0a19-41d7-9f70-e803e312925c |
| service     | platform                             |
| section     | crashdump                            |
| name        | min_available                        |
| value       | 4,5Gi                                |
| personality | None                                 |
| resource    | None                                 |
+-------------+--------------------------------------+

If you need to modify or delete any parameter, perform the following:

1. List the currently configured service parameters.

   [sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-list | grep crashdump
   
   | 3f5d8bc0-26cc-43b5-aeb6-d6a5b5b27035 | platform   | crashdump   | max_files     | 6           | None        | None    |
   | 164b5630-9125-4482-b08d-5b5b80d25e14 | platform   | crashdump   | max_size      | unlimited   | None        | None    |
   | f2a6d3b4-0b9f-40d9-89b1-4e06d425cf79 | platform   | crashdump   | max_used      | 10G         | None        | None    |
   | da4af8a9-0a19-41d7-9f70-e803e312925c | platform   | crashdump   | min_available | 4,5Gi       | None        | None    |

2. Update it or delete it using the UUID.

   [sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-modify platform crashdump max_used='unlimited'
   
   +-------------+--------------------------------------+
   | Property    | Value                                |
   +-------------+--------------------------------------+
   | uuid        | f2a6d3b4-0b9f-40d9-89b1-4e06d425cf79 |
   | service     | platform                             |
   | section     | crashdump                            |
   | name        | max_used                             |
   | value       | unlimited                            |
   | personality | None                                 |
   | resource    | None                                 |
   +-------------+--------------------------------------+

   [sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-delete f2a6d3b4-0b9f-40d9-89b1-4e06d425cf79
   
   Deleted service parameter: f2a6d3b4-0b9f-40d9-89b1-4e06d425cf79

3. List the service-parameter to confirm the new values.

   [sysadmin@controller-0 ~(keystone_admin)]$ system service-parameter-list | grep crashdump
   
   | 164b5630-9125-4482-b08d-5b5b80d25e14 | platform   | crashdump    | max_size         | unlimited  | None        | None     |
   | 3f5d8bc0-26cc-43b5-aeb6-d6a5b5b27035 | platform   | crashdump    | max_files        | 6          | None        | None     |
   | f2a6d3b4-0b9f-40d9-89b1-4e06d425cf79 | platform   | crashdump    | max_used         | 10G        | None
   | da4af8a9-0a19-41d7-9f70-e803e312925c | platform   | crashdump    | min_available    | 4,5Gi      | None        | None     |