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Grammar, punctuation, fixes in Knowledge Base (#1473)
Signed-off-by: Daniel Gray <dng@disroot.org>
This commit is contained in:
d4rklynk
@@ -10,7 +10,7 @@ A [firewall](https://en.wikipedia.org/wiki/Firewall_(computing)) may be used to
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Red Hat distributions (such as Fedora) are typically configured through [firewalld](https://en.wikipedia.org/wiki/Firewalld). Red Hat has plenty of [documentation](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/configuring_and_managing_networking/using-and-configuring-firewalld_configuring-and-managing-networking) regarding this topic. There is also the [Uncomplicated Firewall](https://en.wikipedia.org/wiki/Uncomplicated_Firewall) which can be used as an alternative.
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Consider blocking all ports which are **not** [well known](https://en.wikipedia.org/wiki/Well-known_port#Well-known_ports) or “privileged ports”. That is, ports from 1025 up to 65535. Block both [TCP](https://en.wikipedia.org/wiki/Transmission_Control_Protocol) and [UDP](https://en.wikipedia.org/wiki/User_Datagram_Protocol) after the operating system is installed.
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Consider blocking all ports which are **not** [well-known](https://en.wikipedia.org/wiki/Well-known_port#Well-known_ports) or “privileged ports.” That is, ports from 1025 up to 65535. Block both [TCP](https://en.wikipedia.org/wiki/Transmission_Control_Protocol) and [UDP](https://en.wikipedia.org/wiki/User_Datagram_Protocol) after the operating system is installed.
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If you use Fedora, consider removing the whitelist for [smb](https://en.wikipedia.org/wiki/Server_Message_Block)-client and [mdns](https://en.wikipedia.org/wiki/Multicast_DNS) services if you do not use them.
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@@ -36,7 +36,7 @@ Some distributions like Arch Linux have the [linux-hardened](https://github.com/
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## Linux Kernel Runtime Guard (LKRG)
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LKRG is a kernel module that performs runtime integrity check on the kernel to help detect detect exploits against the kernel. LKRG works in a *post*-detect fashion, attempting to respond to unauthorized modifications to the running Linux kernel. While it is [bypassable by design](https://lkrg.org/), it does stop off-the-shelf malware that does not specifically target LKRG itself. This may make exploits harder to develop and execute on vulnerable systems.
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LKRG is a kernel module that performs runtime integrity check on the kernel to help detect exploits against the kernel. LKRG works in a *post*-detect fashion, attempting to respond to unauthorized modifications to the running Linux kernel. While it is [bypassable by design](https://lkrg.org/), it does stop off-the-shelf malware that does not specifically target LKRG itself. This may make exploits harder to develop and execute on vulnerable systems.
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If you can get LKRG and maintain module updates it provides a worthwhile improvement to security. Debian based distributions can get the LKRG DKMS from KickSecure's secure repository and the [KickSecure documentation](https://www.kicksecure.com/wiki/Linux_Kernel_Runtime_Guard_LKRG) has instructions on how this can be achieved. There is no LKRG package for Fedora yet, however the Qubes OS project has a COPR repository which [may become](https://github.com/QubesOS/qubes-issues/issues/5461) part of the main distribution in the future. Archlinux based systems provide LKRG DKMS modules via an [AUR package](https://aur.archlinux.org/packages/lkrg-dkms).
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@@ -80,7 +80,7 @@ On systems where [`pam_faillock`](https://man7.org/linux/man-pages/man8/pam_tall
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## USB port protection
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To better protect your [USB](https://en.wikipedia.org/wiki/USB) ports from attacks such as [BadUSB](https://en.wikipedia.org/wiki/BadUSB) we recommend [USBGuard](https://github.com/USBGuard/usbguard). USBGuard has [documentation](https://github.com/USBGuard/usbguard#documentation) as does the [Arch Wiki](https://wiki.archlinux.org/title/USBGuard).
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To better protect your [USB](https://en.wikipedia.org/wiki/USB) ports from attacks such as [BadUSB](https://en.wikipedia.org/wiki/BadUSB), we recommend [USBGuard](https://github.com/USBGuard/usbguard). USBGuard has [documentation](https://github.com/USBGuard/usbguard#documentation) as does the [Arch Wiki](https://wiki.archlinux.org/title/USBGuard).
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Another alternative option if you’re using the [linux-hardened](#linux-hardened) is the [`deny_new_usb`](https://github.com/GrapheneOS/linux-hardened/commit/96dc427ab60d28129b36362e1577b6673b0ba5c4) sysctl. See [Preventing USB Attacks with `linux-hardened`](https://blog.lizzie.io/preventing-usb-attacks-with-linux-hardened.html).
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@@ -88,11 +88,11 @@ Another alternative option if you’re using the [linux-hardened](#linux-hardene
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[Secure Boot](https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface#Secure_Boot) can be used to secure the boot process by preventing the loading of [unsigned](https://en.wikipedia.org/wiki/Public-key_cryptography) [UEFI](https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface) drivers or [boot loaders](https://en.wikipedia.org/wiki/Bootloader). Some guidance for this is provided in [this physical security guide](https://madaidans-insecurities.github.io/guides/linux-hardening.html#physical-security) and [this verified boot guide](https://madaidans-insecurities.github.io/guides/linux-hardening.html#verified-boot).
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For further resources on Secure Boot we suggest taking a look at the following for instructional advice:
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For further resources on Secure Boot, we suggest taking a look at the following for instructional advice:
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- The Archwiki’s [Secure Boot](https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot) article. There are two main methods, the first is to use a [shim](https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot#shim), the second more complete way is to [use your own keys](https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot#Using_your_own_keys).
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For background of how Secure Boot works on Linux:
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For the background of how Secure Boot works on Linux:
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- [The Strange State of Authenticated Boot and Disk Encryption on Generic Linux Distributions](https://0pointer.net/blog/authenticated-boot-and-disk-encryption-on-linux.html)
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- [Rod Smith’s Managing EFI Boot Loaders for Linux](https://www.rodsbooks.com/efi-bootloaders/)
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@@ -2,9 +2,9 @@
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title: Linux Overview
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icon: fontawesome/brands/linux
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---
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It is often believed that [open source](https://en.wikipedia.org/wiki/Open-source_software) software is inherently secure because the source code is available. There is an expectation that community verification occurs regularly; however, this isn’t always [the case](https://seirdy.one/2022/02/02/floss-security.html). It does depend on a number of factors, such as project activity, developer experience, level of rigour applied to [code reviews](https://en.wikipedia.org/wiki/Code_review), and how often attention is given to specific parts of the [codebase](https://en.wikipedia.org/wiki/Codebase) that may go untouched for years.
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It is often believed that [open-source](https://en.wikipedia.org/wiki/Open-source_software) software is inherently secure because the source code is available. There is an expectation that community verification occurs regularly; however, this isn’t always [the case](https://seirdy.one/2022/02/02/floss-security.html). It does depend on a number of factors, such as project activity, developer experience, level of rigour applied to [code reviews](https://en.wikipedia.org/wiki/Code_review), and how often attention is given to specific parts of the [codebase](https://en.wikipedia.org/wiki/Codebase) that may go untouched for years.
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At the moment, desktop GNU/Linux does have some areas that could be better improved when compared to their proprietary counterparts, e.g:
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At the moment, desktop GNU/Linux does have some areas that could be better improved when compared to their proprietary counterparts, e.g.:
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- A verified boot chain, unlike Apple’s [Secure Boot](https://support.apple.com/guide/security/startup-security-utility-secc7b34e5b5/web) (with [Secure Enclave](https://support.apple.com/guide/security/secure-enclave-sec59b0b31ff/1/web/1)), Android’s [Verified Boot](https://source.android.com/security/verifiedboot) or Microsoft Windows’s [boot process](https://docs.microsoft.com/en-us/windows/security/information-protection/secure-the-windows-10-boot-process) with [TPM](https://docs.microsoft.com/en-us/windows/security/information-protection/tpm/how-windows-uses-the-tpm). These features and hardware technologies can all help prevent persistent tampering by malware or [evil maid attacks](https://en.wikipedia.org/wiki/Evil_Maid_attack)
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- Strong sandboxing solution such as that found in [macOS](https://developer.apple.com/library/archive/documentation/Security/Conceptual/AppSandboxDesignGuide/AboutAppSandbox/AboutAppSandbox.html), [ChromeOS](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/sandboxing.md), and [Android](https://source.android.com/security/app-sandbox). Commonly used Linux sandboxing solutions such as [Flatpak](https://docs.flatpak.org/en/latest/sandbox-permissions.html) and [Firejail](https://firejail.wordpress.com/) still have a long way to go
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@@ -42,7 +42,7 @@ Traditionally, Linux distributions update by sequentially updating the desired p
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Atomic updating distributions apply updates in full or not at all. Typically, transactional update systems are also atomic.
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A transactional update system creates a snapshot that is made before and after an update is applied. If an update fails at any time (perhaps due to a power failure), the update can be easily rolled back to a “last known good state”.
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A transactional update system creates a snapshot that is made before and after an update is applied. If an update fails at any time (perhaps due to a power failure), the update can be easily rolled back to a “last known good state."
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The Atomic update method is used for immutable distributions like Silverblue, Tumbleweed, and NixOS and can achieve reliability with this model. [Adam Šamalík](https://twitter.com/adsamalik) provided a presentation on how `rpm-ostree` works with Silverblue:
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@@ -52,7 +52,7 @@ The Atomic update method is used for immutable distributions like Silverblue, Tu
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### “Security-focused” distributions
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There is often some confusion about “security-focused” distributions and “pentesting” distributions. A quick search for “the most secure Linux distribution” will often give results like Kali Linux, Black Arch, and Parrot OS. These distributions are offensive penetration testing distributions that bundle tools for testing other systems. They don’t include any “extra security” or defensive mitigations intended for regular use.
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There is often some confusion about “security-focused” distributions and “pentesting” distributions. A quick search for “the most secure Linux distribution” will often give results like Kali Linux, Black Arch and Parrot OS. These distributions are offensive penetration testing distributions that bundle tools for testing other systems. They don’t include any “extra security” or defensive mitigations intended for regular use.
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### Arch-based distributions
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@@ -60,7 +60,7 @@ Arch based distributions are not recommended for those new to Linux, regardless
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For a secure system, you are also expected to have sufficient Linux knowledge to properly set up security for their system such as adopting a [mandatory access control](https://en.wikipedia.org/wiki/Mandatory_access_control) system, setting up [kernel module](https://en.wikipedia.org/wiki/Loadable_kernel_module#Security) blacklists, hardening boot parameters, manipulating [sysctl](https://en.wikipedia.org/wiki/Sysctl) parameters, and knowing what components they need such as [Polkit](https://en.wikipedia.org/wiki/Polkit).
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Anyone using the [Arch User Repository (AUR)](https://wiki.archlinux.org/title/Arch_User_Repository), **must** be comfortable in auditing PKGBUILDs that they install from that service. AUR packages are community-produced content and are not vetted in any way, and therefore are vulnerable to software supply chain attacks, which has in fact happened [in the past](https://www.bleepingcomputer.com/news/security/malware-found-in-arch-linux-aur-package-repository/). AUR should always be used sparingly and often there is a lot of bad advice on various pages which direct people to blindly use [AUR helpers](https://wiki.archlinux.org/title/AUR_helpers) without sufficient warning. Similar warnings apply to using third party Personal Package Archives (PPAs) on Debian based distributions or Community Projects (COPR) on Fedora.
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Anyone using the [Arch User Repository (AUR)](https://wiki.archlinux.org/title/Arch_User_Repository), **must** be comfortable in auditing PKGBUILDs that they install from that service. AUR packages are community-produced content and are not vetted in any way, and therefore are vulnerable to software supply chain attacks, which has in fact happened [in the past](https://www.bleepingcomputer.com/news/security/malware-found-in-arch-linux-aur-package-repository/). AUR should always be used sparingly and often there is a lot of bad advice on various pages which direct people to blindly use [AUR helpers](https://wiki.archlinux.org/title/AUR_helpers) without sufficient warning. Similar warnings apply to use third-party Personal Package Archives (PPAs) on Debian based distributions or Community Projects (COPR) on Fedora.
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If you are experienced with Linux and wish to use an Arch-based distribution, we only recommend Arch Linux proper, not any of its derivatives. We recommend against these two Arch derivatives specifically:
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@@ -87,7 +87,7 @@ Consider using [ZRAM](https://wiki.archlinux.org/title/Swap#zram-generator) or [
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We recommend using a desktop environment that supports the [Wayland](https://en.wikipedia.org/wiki/Wayland_(display_server_protocol)) display protocol as it developed with security [in mind](https://lwn.net/Articles/589147/). Its predecessor, [X11](https://en.wikipedia.org/wiki/X_Window_System), does not support GUI isolation, allowing all windows to [record screen, log and inject inputs in other windows](https://blog.invisiblethings.org/2011/04/23/linux-security-circus-on-gui-isolation.html), making any attempt at sandboxing futile. While there are options to do nested X11 such as [Xpra](https://en.wikipedia.org/wiki/Xpra) or [Xephyr](https://en.wikipedia.org/wiki/Xephyr), they often come with negative performance consequences and are not convenient to set up and are not preferable over Wayland.
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Fortunately, common environments such as [GNOME](https://www.gnome.org), [KDE](https://kde.org), and the window manager [Sway](https://swaywm.org) have support for Wayland. Some distributions like Fedora and Tumbleweed use it by default and some others may do so in the future as X11 is in [hard maintenance mode](https://www.phoronix.com/scan.php?page=news_item&px=X.Org-Maintenance-Mode-Quickly). If you’re using one of those environments it is as easy as selecting the “Wayland” session at the desktop display manager ([GDM](https://en.wikipedia.org/wiki/GNOME_Display_Manager), [SDDM](https://en.wikipedia.org/wiki/Simple_Desktop_Display_Manager)).
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Fortunately, common environments such as [GNOME](https://www.gnome.org), [KDE](https://kde.org), and the window manager [Sway](https://swaywm.org) have support for Wayland. Some distributions like Fedora and Tumbleweed use it by default, and some others may do so in the future as X11 is in [hard maintenance mode](https://www.phoronix.com/scan.php?page=news_item&px=X.Org-Maintenance-Mode-Quickly). If you’re using one of those environments it is as easy as selecting the “Wayland” session at the desktop display manager ([GDM](https://en.wikipedia.org/wiki/GNOME_Display_Manager), [SDDM](https://en.wikipedia.org/wiki/Simple_Desktop_Display_Manager)).
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We recommend **against** using desktop environments or window managers that do not have Wayland support such as Cinnamon (default on Linux Mint), Pantheon (default on Elementary OS), MATE, Xfce, and i3.
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@@ -101,7 +101,7 @@ We **highly recommend** that you install the microcode updates, as your CPU is a
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### MAC Address Randomization
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Many desktop Linux distributions (Fedora, openSUSE etc) will come with [NetworkManager](https://en.wikipedia.org/wiki/NetworkManager), to configure Ethernet and Wi-Fi settings.
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Many desktop Linux distributions (Fedora, openSUSE, etc) will come with [NetworkManager](https://en.wikipedia.org/wiki/NetworkManager), to configure Ethernet and Wi-Fi settings.
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It is possible to [randomize](https://fedoramagazine.org/randomize-mac-address-nm/) the [MAC address](https://en.wikipedia.org/wiki/MAC_address) when using NetworkManager. This provides a bit more privacy on Wi-Fi networks as it makes it harder to track specific devices on the network you’re connected to. It does [**not**](https://papers.mathyvanhoef.com/wisec2016.pdf) make you anonymous.
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@@ -109,7 +109,7 @@ We recommend changing the setting to **random** instead of **stable**, as sugges
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If you are using [systemd-networkd](https://en.wikipedia.org/wiki/Systemd#Ancillary_components), you will need to set [`MACAddressPolicy=random`](https://www.freedesktop.org/software/systemd/man/systemd.link.html#MACAddressPolicy=) which will enable [RFC 7844 (Anonymity Profiles for DHCP Clients)](https://www.freedesktop.org/software/systemd/man/systemd.network.html#Anonymize=).
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There isn’t much point in randomizing the MAC address for Ethernet connections as a system administrator can find you by looking at the port you are using on the [network switch](https://en.wikipedia.org/wiki/Network_switch). Randomizing Wi-Fi MAC addresses depends on support from the Wi-Fi’s firmware.
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There isn’t many points in randomizing the MAC address for Ethernet connections as a system administrator can find you by looking at the port you are using on the [network switch](https://en.wikipedia.org/wiki/Network_switch). Randomizing Wi-Fi MAC addresses depends on support from the Wi-Fi’s firmware.
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### Other Identifiers
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@@ -53,7 +53,7 @@ You can make your own AppArmor profiles, SELinux policies, Bubblewrap profiles,
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### Securing Linux containers
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If you’re running a server you may have heard of Linux Containers, Docker, or Podman which refer to a kind of [OS-level virtualization](https://en.wikipedia.org/wiki/OS-level_virtualization). Containers are more common in server and development environments where individual apps are built to operate independently.
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If you’re running a server, you may have heard of Linux Containers, Docker, or Podman which refer to a kind of [OS-level virtualization](https://en.wikipedia.org/wiki/OS-level_virtualization). Containers are more common in server and development environments where individual apps are built to operate independently.
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[Docker](https://en.wikipedia.org/wiki/Docker_(software)) is one of the most common container solutions. It does not run a proper sandbox, and this means that there is a large kernel attack surface. The [daemon](https://en.wikipedia.org/wiki/Daemon_(computing)) controls everything and [typically](https://docs.docker.com/engine/security/rootless/#known-limitations) runs as root. If it crashes for some reason, all the containers will crash too. The [gVisor](https://en.wikipedia.org/wiki/GVisor) runtime which implements an application level kernel can help limit the number of [syscalls](https://en.wikipedia.org/wiki/System_call) an application can make and can help isolate it from the host’s [kernel](https://en.wikipedia.org/wiki/Kernel_(operating_system)).
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