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synctl - Synapse server control interface


Start, stop or restart synapse server.

synctl {start|stop|restart} [configfile] [-w|--worker=WORKERCONFIG] [-a|--all-processes=WORKERCONFIGDIR]


synctl can be used to start, stop or restart Synapse server. The control operation can be done on all processes or a single worker process.


The value of action should be one of start, stop or restart.
Optional path of the configuration file to use. Default value is homeserver.yaml. The configuration file must exist for the operation to succeed.
Perform start, stop or restart operations on a single worker. Incompatible with -a|--all-processes. Value passed must be a valid worker´s configuration file.
Perform start, stop or restart operations on all the workers in the given directory and the main synapse process. Incompatible with -w|--worker. Value passed must be a directory containing valid work configuration files. All files ending with .yaml extension shall be considered as configuration files and all other files in the directory are ignored.


Configuration file may be generated as follows:

$ python -B -m -c config.yaml --generate-config --server-name=<server name>


Synapse´s architecture is quite RAM hungry currently - we deliberately cache a lot of recent room data and metadata in RAM in order to speed up common requests. We´ll improve this in the future, but for now the easiest way to either reduce the RAM usage (at the risk of slowing things down) is to set the almost-undocumented SYNAPSE_CACHE_FACTOR environment variable. The default is 0.5, which can be decreased to reduce RAM usage in memory constrained enviroments, or increased if performance starts to degrade.
However, degraded performance due to a low cache factor, common on machines with slow disks, often leads to explosions in memory use due backlogged requests. In this case, reducing the cache factor will make things worse. Instead, try increasing it drastically. 2.0 is a good starting value.


This man page was written by Sunil Mohan Adapa <> for Debian GNU/Linux distribution.


synapse_port_db(1), hash_password(1), register_new_matrix_user(1)

August 2020