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% nohang(8) | Linux System Administrator's Manual
NAME
nohang - A sophisticated low memory handler
SYNOPSIS
nohang [OPTION]...
DESCRIPTION
nohang is a highly configurable daemon for Linux which is able to correctly prevent out of memory (OOM) and keep system responsiveness in low memory conditions.
REQUIREMENTS
For basic usage:
- Linux (>= 3.14, since MemAvailable appeared in /proc/meminfo)
- Python (>= 3.3)
To respond to PSI metrics (optional):
- Linux (>= 4.20) with CONFIG_PSI=y
To show GUI notifications (optional):
- notification server (most of desktop environments use their own implementations)
- libnotify (Arch Linux, Fedora, openSUSE) or libnotify-bin (Debian GNU/Linux, Ubuntu)
- sudo if nohang started with UID=0.
OPTIONS
-h, --help
show this help message and exit
-v, --version
show version of installed package and exit
-m, --memload
consume memory until 40 MiB (MemAvailable + SwapFree) remain free, and terminate the process
-c CONFIG, --config CONFIG
path to the config file. This should only be used with one of the following options: --monitor, --tasks, --check
--check
check and show the configuration and exit. This should only be used with -c/--config CONFIG option
--monitor
start monitoring. This should only be used with -c/--config CONFIG option
--tasks
show tasks state and exit. This should only be used with -c/--config CONFIG option
HOW TO CONFIGURE
The program can be configured by editing the config file. The configuration includes the following sections:
- Memory levels to respond to as an OOM threat
- Response on PSI memory metrics
- The frequency of checking the level of available memory (and CPU usage)
- The prevention of killing innocent victims
- Impact on the badness of processes via matching their names, cmdlines and UIDs with regular expressions
- The execution of a specific command or sending any signal instead of sending the SIGTERM signal
- GUI notifications:
- notifications of corrective actions taken
- low memory warnings
- Verbosity
- Misc
Just read the description of the parameters and edit the values. Restart the daemon to apply the changes.
HOW TO TEST
The safest way is to run nohang --memload. This causes memory consumption, and the process will exits before OOM occurs. Another way is to run tail /dev/zero. This causes fast memory comsumption and causes OOM at the end. If testing occurs while nohang is running, these processes should be terminated before OOM occurs.
LOGGING
To view the latest entries in the log (for systemd users):
$ sudo journalctl -eu nohang.service
or
$ sudo journalctl -eu nohang-desktop.service
You can also enable separate_log in the config to logging in /var/log/nohang/nohang.log.