Common Config Classes


Config Classes manage configurations that are too complex to fit into the key + value scheme used by properties. Therefore, there is no common interface to configure all classes. Instead, each class has its own configuration dialog, presenting the specific options it provides. Furthermore, some classes depend on sub-classes (e.g. Boot Configs depend on Qlustar Images). Only the top-level Config Classes are directly assignable to a Config Set or a host. Sub-classes are assigned indirectly via their parent class. Most of the functional subsystems of Qlustar have a dedicated Config Class. Currently, there are five of them: Network, Boot, DHCP, Disk, and Slurm Configs (Slurm is optional) complemented by a single sub-class, Qlustar Images. Please note that the Network Configs has already been described in a previous chapter

Writing Config Files

The Write Files Preview dialog

Many of the configurations managed in the QluMan GUI via Config Classes and sub-classes are translated into automatically generated configuration files located in the filesystem of the head-node(s). While QluMan configuration options are usually saved in the QluMan database immediately after they have been entered in the GUI, the write process of the real configuration files on disk is a separate step, that needs to be explicitly initiated and confirmed.

Each configuration dialog of a Config Class has a Preview button that opens the Write Files window with its own config files already expanded. If a Config Class has no pending changes, the Preview button becomes a View button, while its function remains the same.

The Write Files button.

The Write Files window can also be opened from Manage Cluster  Write Files or via the Write Files button at the bottom right of the main window. This button is an indicator for the presence of pending changes: It is grayed out if there aren’t any, and fully visible otherwise.

No pending changes

Write changed file classes

When the Write Files window is opened, on the left it shows the list of all QluMan Config Classes that may be written. Each Config Class has a status LED. It is red if there are changes pending to be written, otherwise green. The files of all Config Classes with pending changes can be written by clicking the Write Changed button at the bottom. It will be grayed out if there are no changes.

Selecting files to write

Config Classes can also be written individually by setting the check-mark before each class. This converts the button at the bottom to Write Selected. Pressing it will then write the files of all checked classes regardless of whether they have changes or not.

Writing a Config Class without changes is sometimes desirable to restart its related service, like e.g. the slurm daemon for the Slurm Config class.

The actual write command is performed via the Qlustar RXengine. This allows for consistent management of multiple head-nodes e.g. in a high-availability configuration.


Before writing the generated files for each Config Class, they can be inspected by expanding their entry in the tree view. Under the hood, this expansion initiates a request by the GUI to the QluMan server, asking to send the generated files together with a diff against the current files on disk. For the latter to work, the execd on the Headnode needs to be up and running.

The generated files are shown in a tree structure where nodes represent directories and leafs the individual files. For compactness, directories with only one entry are combined

Displaying the diff of pending changes.

A file with no pending changes.

into a single node. Each entry has its own status LED. It’s red if there are changes pending to be written, otherwise green. A red-green LED is shown if some files in a directory have changes and some do not. Selecting a file will show its contents on the right. If changes are pending, a diff of the changes will also be shown below that.

Scanning through all config files

Besides selecting files from the tree, there is also a second method of navigating between files. At the bottom of the right side, there are two arrow buttons that will switch to the previous and next file in the tree respectively. This allows to quickly browse through all files with single clicks without having to move the mouse. Per default, the Prev and Next buttons will cycle through all files. After checking the Only changed files checkbox, only files with pending changes will be switched to.

Refreshing the display after changes were committed.

Changes are not written before having refreshed.

While the Write Files window is open, further changes may have been made to the cluster configuration, either by the current user or another one. The Write Files window will detect this. As a result, a yellow component will be added to all LEDs and the Refresh button at the bottom be activated . Until the latter is clicked, the displayed information will not reflect the latest changes and trying to write will also fail with an error message. This is to prevent the activation of files with a content that is different from what has been previewed.

Generating the files for each Config Class can be an expensive operation on large clusters. This is therefore not done automatically after every change. Instead, the server has a rough idea about what changes will affect each Config Class and will simply flag the relevant ones as being a candidate for having changed files. Generating the actual files is then delayed for 10 seconds and might find that no changes will actually occur.

This delay reduces the load on the server if multiple changes are made within a short time. The downside of it is that the LEDs can turn red or yellow for a short time, even though no actual change exists. Clicking the Refresh button in this situation will abort the delay and generate the files for each Config Class immediately.

Host-specific Configs

Initiating a preview of host specific config files

Preview of host specific config files

Various configurations managed in the QluMan GUI via Config Classes and sub-classes translate into automatically generated configuration files for the individual hosts. In the pre-systemd phase of their boot process, these files will be sent to them and written by their execd. At this stage, there is no general update mechanism concerning these files for running nodes and changes only take effect during the next boot. A preview of the generated configs can be initiated by selecting Preview config from the host’s context menu. More than one host may be selected for this.

Changes to the current config files of a host will only be shown if the host is online. If the host is offline (for example due to network problems) but not powered down, possible changes might not be shown.

Boot Configs

Boot Config dialog

The Boot Config dialog allows to define settings for the PXE/tftp boot server. A boot configuration determines which Qlustar OS image is delivered to a node, and optionally permits the specification of PXELinux commands and/or Linux kernel parameters. When opened, the Boot Config window shows a collapsed tree-list of all boot configs currently defined, sorted by their names.

Note that the default config is special: It applies to any node without a specifically assigned (either through a template or directly) Boot Config. This means, that in the simplest configuration, where all nodes should boot identically, having just the default config will be sufficient.

Changing a Boot Config

By expanding a Boot Config item, the configured Qlustar image, PXELinux command, and kernel parameters become visible. You can change any of the values, by simply selecting a different option from the drop-down menus. In case of kernel parameters, you can also directly edit the entry and save the result by pressing Enter. Furthermore, it is possible to add multiple kernel parameters or remove them through the context menu. Each selected kernel parameter will be added to the kernel command line.

Creating new Boot Configs

The context menu also lets you create new Boot Configs and edit or delete an existing one. Alternatively, a new Boot Config can be created by clicking the New button at the bottom of the dialog. Both, the context menu and the button bring up the New Boot Config dialog. Simply enter the name and description for the new config, select a Qlustar image and (optionally) a PXELinux command. Finally press OK to create it. The new config will then appear in the Boot Config window and will be ready for use.

Pressing the Boot Parameter Editor button at the bottom of the dialog, will bring up a small edit dialog, where kernel parameters can be created, edited, or deleted.

Disk Configs

Qlustar has a powerful mechanism to manage the configuration of disks on a node. It basically allows for any automatic setup of your hard drives including any ZFS/zpool variant, kernel software RAID (md) and LVM setups.

Non-ZFS setups use a mechanism that is partly based on the setup_storage module of FAI. A detailed description of the syntax for disk configurations is available.

Since the OS of a Qlustar net-boot node is always running from RAM, a disk-less configuration is obviously also possible. Valid disk configurations require definitions for two filesystems /var and /scratch, swap space is optional (see examples). To permit the initial formatting of a new disk configuration on a node, it must have assigned the Schedule Format: always generic property during the initial boot.

Creating/editing disk configs

Disk configurations can be managed using the Disk Configs dialog accessible from the main menu Manage Configs  Disk Configs. You can select the config to be viewed/edited from the drop-down menu at the bottom left. A couple of example configurations are created during the installation. Note that there are two special configs: (a) disk-less (not editable or deletable) and (b) default (editable but not deletable). The default config is used for any node that doesn’t have a specific assignment to a disk config (via a Host Template, config set).

The configuration itself can be edited in the text field at the top of the dialog. New configs can be created by choosing New disk config from the drop-down menu. As usual, enter the name of the new config in the text field and fill in the contents and description.

Editing a disk config

To prevent multiple QluMan users from editing the same config simultaneously and overwriting each others changes accidentally, a lock must be acquired for the template by clicking the Edit button. If another user is already editing the config, the button will be ghosted and the tool-tip will show which user is holding a lock for it.

Saving a disk config

After having finished editing a template, don’t forget to save your changes by clicking the Save button. It will be ghosted, if there is nothing to save. You can undo all your changes up to the last time the template was saved by clicking the Undo button. In case another admin has made changes to a disk config while you are viewing or editing it, the Refresh button will become enabled. By clicking it, the updated disk config is shown and you loose any unsaved changes you have already made in your own edit field. To delete a disk config click the Delete button.

Lock expiration pop-up

The template lock expires automatically after some time without activity so that the template is not dead-locked if someone forgets to release the lock. In such a case an info dialog will pop up to notify you about it. By selecting OK a new lock will be requested. If another user is starting to edit the template at exactly that time though, the request will fail and an error dialog will inform you of the failure.

Network Filesystem Exports/Mounts

Network FS Mounts overview

QluMan also supports the configuration and management of Network Filesystem (FS) and bind mounts for cluster nodes. The setup for this consists of two parts:

  1. For a network FS, a Filesystem Exports resource must be defined using the dialog at Manage Cluster→Filesystem Exports.

  2. A Network FS Mounts config must be created using the dialog at Manage Configs  Network FS Mounts.

Such a config may contain multiple network and bind mount definitions. As with other config classes, once defined, it can be assigned to nodes through the Global or a Host Template, Config Set or direct assignment.

Filesystem Exports

Creating a new FS export

The Filesystem Exports dialog shows the list of exported filesystems by name and FS type. Selecting an entry will show the details for this FS export on the right. A new Filesystem Exports resource can be added by clicking the New button. This requires choosing a unique name that will be used inside QluMan to identify the resource. The Resource Name field will turn green if the entered name is unique. QluMan currently supports three types of network filesystems: NFS, Lustre and BeeGFS. The FS type of the resource can be selected from the drop-down menu.

Defining export properties

Saving the export resource

Next the server exporting the FS has to be selected. The default is beosrv-c, the cluster-internal hostname of the head-node, as the most likely server to export a FS. Using the drop-down menu, the server can be selected from a list of servers already used for other exports. To use a new server, the name has to be entered manually. It can be any hostname known to Qluman. The Server label will turn green if the entered name is a known host. This includes all nodes configured in the Enclosure View and any cluster-external host defined in Manage Cluster  Global Settings  Network Settings.

For a Lustre export resource the server(s) to be added are the MGS server(s) where the management target is mounted. If your Lustre FS is setup with high-availability, you can specify multiple MGS servers.

For a BeeGFS export resource the name of the BeeGFS management server is to be entered here.

The remaining options depend on the selected FS type. In case of NFS, the path of the FS to be exported on the server has to be entered. Because the path will later be used in a systemd mount unit file, there are some restrictions on the syntax. For example the path must start with a "/" and must not have a trailing "/". The Path label will turn green if the entered path is acceptable, otherwise it will turn red.

For a Lustre resource, the Lustre FS name has to be specified. Lustre limits this name to eight characters and again, to avoid complications in the systemd mount unit file later, only alphanumeric characters and some punctuation will be accepted.

In the case of BeeGFS, you have the option to define the TCP and UDP ports on which the management server listens for this FS resource. If the management server manages just one BeeGFS FS, the default ports are usually fine.

Once all fields are entered correctly, the OK button will be enabled and the export definition can be added. It will then appear in the Filesystem Exports window.

Networks available for an export

Adding a network for an export

Removing a network for an export

Qluman automatically adds the networks available on the selected server(s) to the Network priorities. Later, when a node boots and requests its config files from the head-node, the networks available on the client are checked against this list and the first common entry is used for the network path via which the FS will be mounted. Shown entries can be removed or additional networks added from the context menu. Entries can also be moved up or down using drag&drop. This is useful e.g. to ensure that an NFS export is mounted via Infiniband/RDMA on all hosts that are connected to the IB fabric and via Ethernet on nodes without IB.

If the selected server is cluster-external, it will obviously not have a choice of network priorities.

Network Filesystem Mounts

Adding a Network FS Mounts config

Config Name

Once Filesystem Exports have been defined, they can be used to configure Network FS Mounts configs. Each config is a collection of filesystems mounts combined with their mount options. As usual, such a config can be assigned to hosts either directly or indirectly through a template. Only one Network FS Mounts config can be assigned per host, so all mounts that should be available on the booted node must be added to it. Click the New Config button to create a new Network FSMounts config.

Select a Network FS Mounts config

Select a Mountpoint

A newly created Network FS Mounts config will be automatically selected for viewing and editing. Previously defined configs may be selected from the drop-down menu in the top left. Below that, the list of mountpoints for the selected config is shown along with the FS type for each mount. Selecting one of the mountpoints will show its configuration details on the right.

Adding/deleting a mount

Select the export resource

A mount definition can be deleted or a new one added to the config from the context menu. To define a new one, enter the path where the FS should be mounted in the Mount Filesystem dialog. Also select one of the Filesystem Exports resources declared earlier from the drop-down menu. In most cases this information is already sufficient. The next time when a node assigned to this Network FS Mounts config boots, it will mount this FS.

Adding a bind mount

Defining the source path of a bind mount

A bind mount can be added in a similar way. However, instead of selecting an external resource to be mounted, the source path of the bind has to be specified. QluMan is unable to verify the existence of the specified, so it is worth to double check before adding the bind mount config.

Advanced common mount options

Advanced common mount options

Overriding the Network

Stop RDMA from being used

Setting custom mount options

To set special options for a FS mount, first select the corresponding mountpoint from the list on the left. Once selected there are advanced options that can be set common to all FS types (except bind mounts have even less).

  • The automatic selection of the network used to mount the FS may be overridden. First the override must be activated by setting the check-mark for Override Network. A network can then be selected from the drop-down menu to force the mount to use this particular one regardless of what the network priorities of the associated export resource say.

  • Qluman will automatically detect if an IB network is being used to mount a Network FS and will use RDMA (remote direct memory access) for improved performance at lower CPU load. To mount a Network FS without using RDMA that feature has to be disabled for the mount by clearing the Allow RDMA checkbox.

  • Last, any option that the mount command accepts for a mount can be set in the Mount Options field. There are too many of them to explain them all here. Please refer to man mount for the full list of possible options and their meaning.

After editing either the the mount options, be sure to press Enter, or click the Save button to save the changes.

Filesystems are only mounted on boot. Any changes made to a Network FS Mounts config of a node will therefore only take effect the next time it boots.

Advanced NFS mount options

Mounting a sub-directory of a resource

For NFS filesystems a sub-directory can be added to the Source Path to mount just a part of the exported FS.

There are also a number of custom mount options specific to NFS. Please refer to man nfs for the full list of possible options and their meaning. After editing either the source path or the mount options, be sure to press Enter, or click the Save button to save the changes.

Advanced Lustre mount options

Lustre mount definition

Specifying Lustre kernel module parameters

For Lustre filesystems, some advanced settings may be set via kernel module parameters. QluMan pre-defines commonly used parameters together with their suggested default values. They may be added using the context-menu in the Kernel Module Options box. Additional options or values can be added using the Kernel Module Options Editor. This works the same way as for generic properties. New options must take the form module_name:option_name. Please refer to the Lustre documentation for a list of available parameters and their meaning.

Per default, new Lustre FS mounts have activated the custom mount option localflock. If another lock behavior is desired, this entry can easily be changed.

Advanced BeeGFS mount options

BeeGFS mount definition

Adding a BeeGFS client option

BeeGFS clients allow a lot of customization. For most options, the default values are sufficient and don’t have to be explicitly set. Anything diverging from the defaults, can be added via the BeeGFS Client Options box. The most likely options to add are quotaEnabled (to enable the support of quota), sysACLsEnabled (to enable the support of POSIX ACLs) and sysXAttrEnabled (to enable the support of extended attributes).

Tooltip explains BeeGFS options

Adding values for BeeGFS options

The pre-defined BeeGFS client options shown by QluMan are automatically generated from the example configuration file distributed in the BeeGFS packages. Each option has a description that can be seen as a tool-tip when hovering over an option that was already selected. The same description is also shown in the BeeGFS Client Options Editor for the option that is selected there. The editor can be opened by clicking the BeeGFS Client Options Editor button and works the same way as for generic properties,

For options where a default value is provided in the example config file, this value will be pre-defined and immutable in QluMan’s BeeGFS Client Options Editor. In case of boolean options, both true and false will be pre-defined regardless of the default. For other options, additional values must be added using the editor, before they can be assigned to a BeeGFS mount config entry.

Options without a default, like e.g. connAuthFile, will have no value pre-defined and won’t show up in the context-menu, unless a value is added through the editor.