.TH nohang 8

.SH NAME

nohang \- A sophisticated low memory handler

.SH SYNOPSIS
.B nohang
.RB [ OPTION ]...

.SH 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.

.SH REQUIREMENTS

.B For basic usage:

    - Linux 3.14+ (since MemAvailable appeared in /proc/meminfo)

    - Python 3.3+ (not tested with previous)

.B To show GUI notifications:

    - Notification server (most of desktop environments use their own implementations)

    - libnotify (Fedora, Arch Linux) or libnotify-bin (Debian GNU/Linux, Ubuntu)

    - sudo if nohang started with UID=0

.B To use PSI:

    - It needs Linux 4.20+ with CONFIG_PSI=y.

.SH 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

.SH HOW TO CONFIGURE

The program can be configured by editing the config file.

.B 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.

Please restart nohang to apply the changes.

Default path to the config after installing is /etc/nohang/nohang.conf.

.SH 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.

.SH LOGGING

To view the latest entries in the log (for systemd users):

$ sudo journalctl -eu nohang

See also man journalctl.

You can also enable separate_log in the config to logging in /var/log/nohang/nohang.log.

.SH SEE ALSO

https://github.com/hakavlad/nohang