CHECKPOINT(5)

NAME
checkpoint - xxQS_NAMExx checkpointing environment configuration file format

DESCRIPTION
Checkpointing is a facility to save the complete status of an executing program or job and to restore and restart from this so called checkpoint at a later point of time if the original program or job was halted, e.g. through a system crash.

xxQS_NAMExx provides various levels of checkpointing support (see The checkpointing environment described here is a means to configure the different types of checkpointing in use for your xxQS_NAMExx cluster or parts thereof. For that purpose you can define the operations which have to be executed in initiating a checkpoint generation, a migration of a checkpoint to another host or a restart of a checkpointed application as well as the list of queues which are eligible for a checkpointing method.

Supporting different operating systems may easily force xxQS_NAMExx to introduce operating system dependencies for the configuration of the checkpointing configuration file and updates of the supported operating system versions may lead to frequently changing implementation details. Please refer to the <xxqs_name_sxx_root>/ckpt directory for more information.

Please use the -ackpt, -dckpt, -mckpt or -sckpt options to the command to manipulate checkpointing environments from the command-line or use the corresponding dialogue for X-Windows based interactive configuration.

Note, xxQS_NAMExx allows backslashes (\) be used to escape newline (\newline) characters. The backslash and the newline are replaced with a space (" ") character before any interpretation.

FORMAT
The format of a checkpoint file is defined as follows:

  ckpt_name
The name of the checkpointing environment as defined for ckpt_name in -ckpt switch or for the options mentioned above.

  interface
The type of checkpointing to be used. Currently, the following types are valid:

hibernator
    The Hibernator kernel level checkpointing is interfaced.

cpr The SGI kernel level checkpointing is used.

cray-ckpt
    The Cray kernel level checkpointing is assumed.

transparent
    xxQS_NAMExx assumes that the jobs submitted with reference to this checkpointing interface use a checkpointing library such as provided by the public domain package Condor.

userdefined
    xxQS_NAMExx assumes that the jobs submitted with reference to this checkpointing interface perform their private checkpointing method.

application-level
    Uses all of the interface commands configured in the checkpointing object like in the case of one of the kernel level checkpointing interfaces (cpr, cray-ckpt, etc.) except for the restart_command (see below), which is not used (even if it is configured) but the job script is invoked in case of a restart instead.

  ckpt_command
A command-line type command string to be executed by xxQS_NAMExx in order to initiate a checkpoint.

  migr_command
A command-line type command string to be executed by xxQS_NAMExx during a migration of a checkpointing job from one host to another.

  restart_command
A command-line type command string to be executed by xxQS_NAMExx when restarting a previously checkpointed application.

  clean_command
A command-line type command string to be executed by xxQS_NAMExx in order to cleanup after a checkpointed application has finished.

  ckpt_dir
A file system location to which checkpoints of potentially considerable size should be stored.

  ckpt_signal
A Unix signal to be sent to a job by xxQS_NAMExx to initiate a checkpoint generation. The value for this field can either be a symbolic name from the list produced by the -l option of the command or an integer number which must be a valid signal on the systems used for checkpointing.

  when
The points of time when checkpoints are expected to be generated. Valid values for this parameter are composed by the letters s, m, x and r and any combinations thereof without any separating character in between. The same letters are allowed for the -c option of the command which will overwrite the definitions in the used checkpointing environment. The meaning of the letters is defined as follows:

s   A job is checkpointed, aborted and if possible migrated if the corresponding is shut down on the job's machine.

m   Checkpoints are generated periodically at the min_cpu_interval interval defined by the queue (see in which a job executes.

x   A job is checkpointed, aborted and if possible migrated as soon as the job gets suspended (manually as well as automatically).

r   A job will be rescheduled (not checkpointed) when the host on which the job currently runs went into unknown state and the time interval reschedule_unknown (see defined in the global/local cluster configuration will be exceeded.

RESTRICTIONS
Note, that the functionality of any checkpointing, migration or restart procedures provided by default with the xxQS_NAMExx distribution as well as the way how they are invoked in the ckpt_command, migr_command or restart_command parameters of any default checkpointing environments should not be changed or otherwise the functionality remains the full responsibility of the administrator configuring the checkpointing environment. xxQS_NAMExx will just invoke these procedures and evaluate their exit status. If the procedures do not perform their tasks properly or are not invoked in a proper fashion, the checkpointing mechanism may behave unexpectedly, xxQS_NAMExx has no means to detect this.

SEE ALSO

COPYRIGHT
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