grsecurity is a chess suite of the Linux kernel with a focus on improving security. While grsecurity offers various protection strategies to stop even partial (0-day) errors – additional investigations, random linking (more than a repeated kernel), memory write access protection.
grsecurity is actually a set of security patches for my Linux kernel.
protects kernels. Regular Debian kernels, even those from SE Linux, are open to many kernel bugs if the bug is not fixed. While grsecurity applies various protection strategies to stop even other (0-day) errors – additional detections, layout randomization (more regular, depending on the kernel), memory write access protection.
provides RBAC protection similar to SE like Linux ( TODO: Compare ) This must be configured in the user area to have any effect.
protect applications from cryptic bugs by changing their RO memory ( reading or executing), randomizing their layout and providing different help on the sidese kernels to these companies
Make sure the chroot becomes real jail chroot
various security updates
As of 2017-2005, hot releases of grsecurity have not been published recently, and therefore no longer exist in Debian.
Grsecurity on Wikibooks
Is Grsecurity free?
A: Grsecurity is fully compatible with the Linux kernel license, GPLv2. Because grsecurity is provided in As a fix to the source code, it is no longer possible under the terms of this GPL to offer a free version with the actual restriction of its use for any purpose other than evaluation.
Wikipedia: grsecurity
Usage (historical) in Debian
Gr Security Packages
How do I reset my spa control panel?
linux-image-grsec: predefined images (removed in 2018-04)
How do I troubleshoot my spa control panel?
linux-patch-grsecurity2: *very obsolete* , only Patches you can make yourself
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Note that they probably won’t be tuned for security/performance and above, as is usually the case when building grsec/PaX support for the Linux kernel at the same time.
Maintain PaX Indicators
Subscribe to a nice toolkit called paxrat to maintain and maintain PaX banners for binary files. It supports some usage situations that paxctld does not support, eg. Live operating roomsSystems (SquashFS).
How do you test a circuit board on a hot tub?
However, paxctld seems to do the job and is the official tool.
Origin
How do you troubleshoot a hot tub circuit board?
See Creating a custom kernel on a “clean” kernel site
Corsac Repository
Korsac, a security researcher working with Debian, provided kernels with grsecurity fixes for running Debian in
protects kernels. Regular Debian kernels, even those from SE Linux, are open to many kernel bugs if the bug is not fixed. While grsecurity applies various protection strategies to stop even other (0-day) errors – additional detections, layout randomization (more regular, depending on the kernel), memory write access protection. 
Make sure the chroot becomes real jail chroot
various security updates 
