oomd.conf - Man Page

These files configure the various parameters of the systemd(1) userspace out-of-memory (OOM) killer, systemd-oomd.service(8). See systemd.syntax(7) for a general description of the syntax.

The default configuration is set during compilation, so configuration is only needed when it is necessary to deviate from those defaults. The main configuration file is loaded from one of the listed directories in order of priority, only the first file found is used: /etc/systemd/, /run/systemd/, /usr/local/lib/systemd/ ^[1], /usr/lib/systemd/. The vendor version of the file contains commented out entries showing the defaults as a guide to the administrator. Local overrides can also be created by creating drop-ins, as described below. The main configuration file can also be edited for this purpose (or a copy in /etc/ if it's shipped under /usr/), however using drop-ins for local configuration is recommended over modifications to the main configuration file.

In addition to the main configuration file, drop-in configuration snippets are read from /usr/lib/systemd/*.conf.d/, /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/. Those drop-ins have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files.

When packages need to customize the configuration, they can install drop-ins under /usr/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. Drop-ins have to be used to override package drop-ins, since the main configuration file has lower precedence. It is recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering. This also defines a concept of drop-in priorities to allow OS vendors to ship drop-ins within a specific range lower than the range used by users. This should lower the risk of package drop-ins overriding accidentally drop-ins defined by users. It is recommended to use the range 10-40 for drop-ins in /usr/ and the range 60-90 for drop-ins in /etc/ and /run/, to make sure that local and transient drop-ins take priority over drop-ins shipped by the OS vendor.

To disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file.

The following options are available in the [OOM] section:

SwapUsedLimit=

Sets the limit for memory and swap usage on the system before systemd-oomd will take action. If the fraction of memory used and the fraction of swap used on the system are both more than what is defined here, systemd-oomd will act on eligible descendant control groups with swap usage greater than 5% of total swap, starting from the ones with the highest swap usage. Which control groups are monitored and what action gets taken depends on what the unit has configured for ManagedOOMSwap=. Takes a value specified in percent (when suffixed with "%"), permille ("‰") or permyriad ("‱"), between 0% and 100%, inclusive. Defaults to 90%.

Added in version 247.

DefaultMemoryPressureLimit=

Sets the limit for memory pressure on the unit's control group before systemd-oomd will take action. A unit can override this value with ManagedOOMMemoryPressureLimit=. The memory pressure for this property represents the fraction of time in a 10 second window in which all tasks in the control group were delayed. For each monitored control group, if the memory pressure on that control group exceeds the limit set for longer than the duration set by DefaultMemoryPressureDurationSec=, systemd-oomd will act on eligible descendant control groups, starting from the ones with the most reclaim activity to the least reclaim activity. Which control groups are monitored and what action gets taken depends on what the unit has configured for ManagedOOMMemoryPressure=. Takes a fraction specified in the same way as SwapUsedLimit= above. Defaults to 60%.

Added in version 247.

DefaultMemoryPressureDurationSec=

Sets the amount of time a unit's control group needs to have exceeded memory pressure limits before systemd-oomd will take action. Memory pressure limits are defined by DefaultMemoryPressureLimit= and ManagedOOMMemoryPressureLimit=. Must be set to 0, or at least 1 second. Defaults to 30 seconds when unset or 0.

Added in version 248.

systemd(1), systemd.resource-control(5), systemd-oomd.service(8), oomctl(1)

1.

💣💥🧨💥💥💣 Please note that those configuration files must be available at all times. If /usr/local/ is a separate partition, it may not be available during early boot, and must not be used for configuration.

oomctl(1), systemd.directives(7), systemd.index(7), systemd-oomd.service(8), systemd.resource-control(5).

The man page oomd.conf.d(5) is an alias of oomd.conf(5).