### Conditional Configuration Example

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Demonstrates how to use '@' for conditional configuration based on the config-id. Lines starting with '@' followed by an ID are included only if the config-id matches. '@^' is used for negative matching.

```keepalived
    global_defs {
        @main   router_id main_router
        @backup router_id backup_router
    }
    ...
    vrrp_instance VRRP {
        ...
        @main    unicast_src_ip 1.2.3.4
        @backup  unicast_src_ip 1.2.3.5
        @backup2 unicast_src_ip 1.2.3.6
        unicast_peer {
            @^main    1.2.3.4
            @^backup  1.2.3.5
            @^backup2 1.2.3.6
        }
        ...
    }
```

--------------------------------

### Enable and Start Keepalived Service with systemd

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Enable the keepalived service to start automatically at boot and start it immediately using systemctl.

```bash
systemctl enable --now keepalived
```

--------------------------------

### Enable and Start Keepalived Service

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/quick-start.md

Enable Keepalived to start on boot and start the service immediately on both nodes.

```bash
# systemctl enable --now keepalived
```

--------------------------------

### Install Prerequisites on Debian/Ubuntu

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install essential build tools and development libraries required for compiling Keepalived from source on Debian/Ubuntu systems.

```bash
apt-get install build-essential pkg-config curl gcc autoconf automake libssl-dev \
    libnl-3-dev libnl-genl-3-dev libsnmp-dev libnl-route-3-dev libnfnetlink-dev \
    iptables-dev* libipset-dev libsnmp-dev libmagic-dev libglib2.0-dev libpcre2-dev \
    libnftnl-dev libmnl-dev libsystemd-dev libkmod-dev
```

--------------------------------

### Install Prerequisites on Archlinux

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install required libraries for compiling Keepalived from source on Archlinux.

```bash
pacman -S ipset libnfnetlink libnl1 pcre-2
```

--------------------------------

### Download, Build, and Install Keepalived from Source

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Download the Keepalived source tarball using curl, extract it, configure the build, compile the package, and install it using make.

```bash
curl --location --progress https://www.keepalived.org/software/keepalived-2.3.4.tar.gz | tar xz
    cd keepalived-2.3.4
    ./configure
    make
    sudo make install
```

--------------------------------

### Start and Enable Keepalived Service

Source: https://github.com/acassen/keepalived/blob/master/README.md

Enables Keepalived to start on boot and starts the service immediately. This command should be run on both master and backup nodes.

```sh
sudo systemctl enable --now keepalived
```

--------------------------------

### Install Prerequisites on Alpine Linux

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install essential build tools and development libraries required for compiling Keepalived from source on Alpine Linux.

```bash
autoconf automake iptables-dev ipset-dev libnfnetlink-dev libnl3-dev musl-dev 
        libnftnl-dev file-dev pcre2-dev
      and
        openssl-dev or libressl-dev
```

--------------------------------

### Build Keepalived from Source

Source: https://github.com/acassen/keepalived/blob/master/README.md

Clones the Keepalived repository, navigates into the directory, configures the build, and installs the software. Requires build tools and libraries listed in the INSTALL file.

```sh
git clone https://github.com/acassen/keepalived.git
cd keepalived
./configure
make && sudo make install
```

--------------------------------

### Conditional Parameter Substitution Example

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Shows how parameter substitution can be used with conditional configuration directives like @main and @backup.

```keepalived
@main $PRIORITY=240
@backup $PRIORITY=200
...
vrrp_instance VI_0 {
    priority $PRIORITY
}

will produce:
    ...
    vrrp_instance VI_0 {
        priority 240
    }
if the config_id is main.
```

--------------------------------

### Install Prerequisites on RHEL/CentOS/Fedora

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install essential build tools and development libraries required for compiling Keepalived from source on RHEL-based systems. Replace dnf with yum on older systems.

```bash
dnf install gcc make autoconf automake openssl-devel libnl3-devel \
    iptables-devel ipset-devel net-snmp-devel libnfnetlink-devel file-devel \
    glib2-devel pcre2-devel libnftnl-devel libmnl-devel systemd-devel kmod-devel
```

--------------------------------

### Serve MkDocs Website Locally for Debugging

Source: https://github.com/acassen/keepalived/blob/master/www/README.md

Starts a local development server to preview the MkDocs website. Changes can be debugged by browsing to http://localhost:8000/.

```bash
$ mkdocs serve
```

--------------------------------

### Keepalived Syslog Output Example

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/programs-synopsis.md

This is an example of the log messages generated by Keepalived when it starts and loads its configuration. It shows global definitions, SSL settings, LVS topology, and health checker status.

```log
Jun 7 18:17:03 lvs1 Keepalived: Starting Keepalived v0.6.1 (06/13, 2002)
Jun 7 18:17:03 lvs1 Keepalived: Configuration is using : 92013 Bytes
Jun 7 18:17:03 lvs1 Keepalived: ------< Global definitions >------
Jun 7 18:17:03 lvs1 Keepalived: LVS ID = LVS_PROD
Jun 7 18:17:03 lvs1 Keepalived: Smtp server = 192.168.200.1
Jun 7 18:17:03 lvs1 Keepalived: Smtp server connection timeout = 30
Jun 7 18:17:03 lvs1 Keepalived: Email notification from = keepalived@domain.com
Jun 7 18:17:03 lvs1 Keepalived: Email notification = alert@domain.com
Jun 7 18:17:03 lvs1 Keepalived: Email notification = 0633556699@domain.com
Jun 7 18:17:03 lvs1 Keepalived: ------< SSL definitions >------
Jun 7 18:17:03 lvs1 Keepalived: Using autogen SSL context
Jun 7 18:17:03 lvs1 Keepalived: ------< LVS Topology >------
Jun 7 18:17:03 lvs1 Keepalived: System is compiled with LVS v0.9.8
Jun 7 18:17:03 lvs1 Keepalived: VIP = 10.10.10.2, VPORT = 80
Jun 7 18:17:03 lvs1 Keepalived: VirtualHost = www.domain1.com
Jun 7 18:17:03 lvs1 Keepalived: delay_loop = 6, lb_algo = rr
Jun 7 18:17:03 lvs1 Keepalived: persistence timeout = 50
Jun 7 18:17:04 lvs1 Keepalived: persistence granularity = 255.255.240.0
Jun 7 18:17:04 lvs1 Keepalived: protocol = TCP
Jun 7 18:17:04 lvs1 Keepalived: lb_kind = NAT
Jun 7 18:17:04 lvs1 Keepalived: sorry server = 192.168.200.200:80
Jun 7 18:17:04 lvs1 Keepalived: RIP = 192.168.200.2, RPORT = 80, WEIGHT = 1
Jun 7 18:17:04 lvs1 Keepalived: RIP = 192.168.200.3, RPORT = 80, WEIGHT = 2
Jun 7 18:17:04 lvs1 Keepalived: VIP = 10.10.10.3, VPORT = 443
Jun 7 18:17:04 lvs1 Keepalived: VirtualHost = www.domain2.com
Jun 7 18:17:04 lvs1 Keepalived: delay_loop = 3, lb_algo = rr
Jun 7 18:17:04 lvs1 Keepalived: persistence timeout = 50
Jun 7 18:17:04 lvs1 Keepalived: protocol = TCP
Jun 7 18:17:04 lvs1 Keepalived: lb_kind = NAT
Jun 7 18:17:04 lvs1 Keepalived: RIP = 192.168.200.4, RPORT = 443, WEIGHT = 1
Jun 7 18:17:04 lvs1 Keepalived: RIP = 192.168.200.5, RPORT = 1358, WEIGHT = 1
Jun 7 18:17:05 lvs1 Keepalived: ------< Health checkers >------
Jun 7 18:17:05 lvs1 Keepalived: 192.168.200.2:80
Jun 7 18:17:05 lvs1 Keepalived: Keepalive method = HTTP_GET
Jun 7 18:17:05 lvs1 Keepalived: Connection timeout = 3
Jun 7 18:17:05 lvs1 Keepalived: Nb get retry = 3
Jun 7 18:17:05 lvs1 Keepalived: Delay before retry = 3
Jun 7 18:17:05 lvs1 Keepalived: Checked url = /testurl/test.jsp,
Jun 7 18:17:05 lvs1 Keepalived: digest = 640205b7b0fc66c1ea91c463fac6334d
Jun 7 18:17:05 lvs1 Keepalived: 192.168.200.3:80
Jun 7 18:17:05 lvs1 Keepalived: Keepalive method = HTTP_GET
Jun 7 18:17:05 lvs1 Keepalived: Connection timeout = 3
Jun 7 18:17:05 lvs1 Keepalived: Nb get retry = 3
Jun 7 18:17:05 lvs1 Keepalived: Delay before retry = 3
Jun 7 18:17:05 lvs1 Keepalived: Checked url = /testurl/test.jsp,
Jun 7 18:17:05 lvs1 Keepalived: digest = 640205b7b0fc66c1ea91c463fac6334c
Jun 7 18:17:05 lvs1 Keepalived: Checked url = /testurl2/test.jsp,
Jun 7 18:17:05 lvs1 Keepalived: digest = 640205b7b0fc66c1ea91c463fac6334c
Jun 7 18:17:06 lvs1 Keepalived: 192.168.200.4:443
Jun 7 18:17:06 lvs1 Keepalived: Keepalive method = SSL_GET
Jun 7 18:17:06 lvs1 Keepalived: Connection timeout = 3
Jun 7 18:17:06 lvs1 Keepalived: Nb get retry = 3
Jun 7 18:17:06 lvs1 Keepalived: Delay before retry = 3
Jun 7 18:17:06 lvs1 Keepalived: Checked url = /testurl/test.jsp,
Jun 7 18:17:05 lvs1 Keepalived: digest = 640205b7b0fc66c1ea91c463fac6334d
Jun 7 18:17:06 lvs1 Keepalived: Checked url = /testurl2/test.jsp,
Jun 7 18:17:05 lvs1 Keepalived: digest = 640205b7b0fc66c1ea91c463fac6334d
Jun 7 18:17:06 lvs1 Keepalived: 192.168.200.5:1358
Jun 7 18:17:06 lvs1 Keepalived: Keepalive method = TCP_CHECK
Jun 7 18:17:06 lvs1 Keepalived: Connection timeout = 3
Jun 7 18:17:06 lvs1 Keepalived: Registering Kernel netlink reflector
```

--------------------------------

### Start Keepalived Daemon

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/programs-synopsis.md

Use this command to start the Keepalived service on systems using systemd.

```bash
# systemctl start keepalived
```

--------------------------------

### Setting up Test Environment with mk_if Script

Source: https://github.com/acassen/keepalived/blob/master/www/docs/release-notes/Release-2.1.4.md

This snippet is part of the 'mk_if' script, which has been extended to provide a more flexible test environment setup.

```bash
#!/bin/sh
#
# mk_if
#
# This script is used to set up a test environment for keepalived.
# It is not intended for use in production.
#
# Usage: mk_if <interface> <ipaddr>
#
# Example: mk_if eth0 192.168.1.100
#

if [ $# -ne 2 ]; then
    echo "Usage: $0 <interface> <ipaddr>"
    exit 1
fi

INTERFACE=$1
IPADDR=$2

# Add IP address to interface
/sbin/ip addr add $IPADDR/24 dev $INTERFACE

# Bring interface up
/sbin/ip link set $INTERFACE up

# Add default route
/sbin/ip route add default via 192.168.1.1

# Enable IP forwarding
echo 1 > /proc/sys/net/ipv4/ip_forward

exit 0
```

--------------------------------

### Example iptables logging rule

Source: https://github.com/acassen/keepalived/blob/master/www/docs/Keepalived-LVS-NAT-Director-ProxyArp-Firewall-HOWTO.html

This example shows how to log firewall hits to the system logs with a default log level. You can add a custom log prefix by appending '--log-prefix "YourPrefix"' to the rule.

```bash
/sbin/iptables -A INPUT -i $EXTIF -p tcp -s 1.2.3.4 $LOG
```

--------------------------------

### Install DBUS Support Prerequisites on RHEL/CentOS/Fedora

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install the glib2 development library for DBUS support when compiling Keepalived from source on RHEL-based systems.

```bash
dnf install glib2-devel
```

--------------------------------

### Install Keepalived on Debian

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Use apt-get to install the keepalived package and its dependencies from the distribution's repositories.

```bash
apt-get install keepalived
```

--------------------------------

### Install Keepalived on Debian/Ubuntu and RHEL/Fedora

Source: https://github.com/acassen/keepalived/blob/master/README.md

Installs Keepalived using the system's package manager. Use the appropriate command for your distribution.

```sh
sudo apt install keepalived     # Debian / Ubuntu
sudo dnf install keepalived     # RHEL / Fedora / Rocky
```

--------------------------------

### Install JSON Support Prerequisites on RHEL/CentOS/Fedora

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install the json-c development library for JSON support when compiling Keepalived from source on RHEL-based systems.

```bash
dnf install json-c-devel
```

--------------------------------

### Build and Install Keepalived

Source: https://github.com/acassen/keepalived/blob/master/www/docs/LVS-NAT-Keepalived-HOWTO.html

Compiles and installs Keepalived from source. Ensure all necessary development libraries and header files are present before running.

```bash
tar xzvf keepalived-0.7.1.tar.gz; cd keepalived-0.7.1; ./configure; make; make install
```

--------------------------------

### Nested Multiline Parameter Substitution Example

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Demonstrates nested multiline parameter definitions, creating complex configurations like virtual servers with multiple real servers.

```keepalived
$RS= \
    real_server 192.168.${VS_NUM}.${RS_NUM} 80 { \
        weight 1 \
        inhibit_on_failure \
        smtp_alert \
        MISC_CHECK { \
            misc_path "${_PWD}/scripts/vs.sh RS_misc.${INST}.${VS_NUM}.${RS_NUM}.0 10.0.${VS_NUM}.4:80->192.168.${VS_NUM}.${RS_NUM}:80" \
        } \

        MISC_CHECK { \
            misc_path "${_PWD}/scripts/vs.sh RS_misc.${INST}.${VS_NUM}.${RS_NUM}.1 10.0.${VS_NUM}.4:80->192.168.${VS_NUM}.${RS_NUM}:80" \
        } \

        notify_up "${_PWD}/scripts/notify.sh RS_notify.${INST}.${VS_NUM}.${RS_NUM} UP 10.0.${VS_NUM}.4:80->192.168.${VS_NUM}.${RS_NUM}:80" \

        notify_down "${_PWD}/scripts/notify.sh RS_notify.${INST}.${VS_NUM}.${RS_NUM} DOWN 10.0.${VS_NUM}.4:80->192.168.${VS_NUM}.${RS_NUM}:80" \

    }

$VS= \
    virtual_server 10.0.${VS_NUM}.4 80 { \
        quorum 2 \
        quorum_up "${_PWD}/scripts/notify.sh VS_notify.${INST} UP 10.0.${VS_NUM}.4:80" \
        quorum_down "${_PWD}/scripts/notify.sh VS_notify.${INST} DOWN 10.0.${VS_NUM}.4:80" \
        $RS_NUM=1 \
        $RS \
        $RS_NUM=2 \
        $RS \
        $RS_NUM=3 \
        $RS \
    }

$VS_NUM=0
$ALPHA=alpha
$VS

$VS_NUM=1
$ALPHA=
$VS
```

--------------------------------

### Install Keepalived on Debian/Ubuntu

Source: https://github.com/acassen/keepalived/blob/master/www/docs/download.md

Use this command to install Keepalived on Debian-based systems like Ubuntu.

```shell
sudo apt install keepalived
```

--------------------------------

### Install Keepalived on RHEL/Fedora/Rocky

Source: https://github.com/acassen/keepalived/blob/master/www/docs/download.md

Use this command to install Keepalived on RHEL, Fedora, or Rocky Linux.

```shell
sudo dnf install keepalived
```

--------------------------------

### Example SuSE 8.0 Keepalived Startup Script

Source: https://github.com/acassen/keepalived/blob/master/www/docs/LVS-NAT-Keepalived-HOWTO.html

This is a template for an LSB-compliant service control script for Keepalived on SuSE 8.0. It includes standard init info directives.

```shell
#! /bin/sh
# Copyright (c) 1995-2002 SuSE Linux AG, Nuernberg, Germany.
# All rights reserved.
#
# Author of template: Kurt Garloff <feedback@suse.de>
# Modified for keepalived by Adam Fletcher <adamf+keepalived@csh.rit.edu>
#
# /etc/init.d/keepalived
#
#
# LSB compliant service control script; see [http://www.linuxbase.org/spec/]
#
# System startup script for some example service or daemon keepalived (template)
#
### BEGIN INIT INFO
# Provides: keepalived
# Required-Start: $remote_fs $syslog
# Required-Stop:� $remote_fs $syslog
# Default-Start:� 3 5
# Default-Stop:�� 0 1 2 6
# Description:��� Start keepalived to allow XY and provide YZ
#������ continued on second line by '#<TAB>'
### END INIT INFO

```

--------------------------------

### Example iptables logging rule with custom prefix

Source: https://github.com/acassen/keepalived/blob/master/www/docs/Keepalived-LVS-NAT-Director-ProxyArp-Firewall-HOWTO.html

This example demonstrates how to log firewall hits with a custom log prefix. The '$LOG' variable is defined to include the '-j LOG --log-level 6' options.

```bash
/sbin/iptables -A INPUT -i $EXTIF -p tcp -s 3.4.5.6 $LOG --log-prefix "Some Hacker! :"
```

--------------------------------

### Nested Sequence Blocks Example

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Demonstrates nesting multiple sequence blocks to generate complex configurations, such as nested IPv6 addresses.

```keepalived
   Another example:

	virtual_ipaddress {
	    ~SEQx(AD2, 0x90, 0x10, 0xc0) ~SEQx(AD1, 0x12, -1, 0x0c) fe81::10:${AD2}:${AD1}
	}
```

--------------------------------

### Install SNMP Support Prerequisites on Archlinux

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install net-snmp package for SNMP support on Archlinux when compiling Keepalived from source.

```bash
pacman -S net-snmp
```

--------------------------------

### Recursive Parameter Substitution Example

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Demonstrates how parameter substitution can be recursive. Note the use of braces when parameters are not followed by whitespace.

```keepalived
$ADDRESS_BASE=10.2.${ADDRESS_BASE_SUB}
$ADDRESS_BASE_SUB=0
${ADDRESS_BASE}.100/32
$ADDRESS_BASE_SUB=10
${ADDRESS_BASE}.100/32

will produce:
    10.2.0.100/32
    10.2.10.100/32
```

--------------------------------

### Create and Activate Virtual Environment

Source: https://github.com/acassen/keepalived/blob/master/www/README.md

Generates a local Python virtual environment and installs all MkDocs Material dependencies within it. This isolates project dependencies.

```bash
$ python3 -m venv .venv
$ . .venv/bin/activate
$ pip install "mkdocs-material[all]"
```

--------------------------------

### Example Keepalived Configuration Summary with SNMP

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/snmp-support.md

This output shows a typical configuration summary during Keepalived compilation, indicating that SNMP support is enabled and listing relevant libraries.

```text
./configure --prefix=/usr/local/keepalived-2.3.4 --enable-snmp
Keepalived configuration
------------------------
Keepalived version       : 2.3.4
Compiler                 : gcc
Compiler flags           : -g -O2 -I/usr/include/libnl3
Extra Lib                : -Wl,-z,relro -Wl,-z,now -L/usr/lib64
    -lnetsnmpagent -lnetsnmphelpers -lnetsnmpmibs -lnetsnmp -Wl,-E
    -Wl,-rpath,/usr/lib64/perl5/CORE -lssl -lcrypto -lcrypt  -lnl-genl-3 -lnl-3
Use IPVS Framework       : Yes
IPVS sync daemon support : Yes
IPVS use libnl           : Yes
fwmark socket support    : Yes
Use VRRP Framework       : Yes
Use VRRP VMAC            : Yes
SNMP support             : Yes
SHA1 support             : No
Use Debug flags          : No
```

--------------------------------

### List Block Example (Multiple Variables)

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Allows substituting multiple variables simultaneously from corresponding lists of values. Useful for generating configurations with multiple dynamic parameters.

```keepalived
    ~LST({IP, IP1}, {10,1},{20,4},{5,6},{12,8}) 192.168.${IP}.${IP1}

would produce:

    192.168.10.1
    192.168.20.4
    192.168.5.6
    192.168.12.8
```

--------------------------------

### Quoted String Example 2

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Shows how nested quotes are handled, resulting in multiple strings when inner quotes are present.

```text
'abcd "efg h jkl" mnop'
```

--------------------------------

### Install SNMP Support Prerequisites on Alpine Linux

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Install net-snmp development package for SNMP support on Alpine Linux when compiling Keepalived from source. Note the dependency on libressl-dev.

```bash
net-snmp-dev (requires libressl-dev and not openssl-dev)
```

--------------------------------

### Interpreted Script Parameters

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Shows the interpreted values of the parameters passed to the notify_master script in the previous example.

```text
' spaces\x20file ', '"s p a c e "', 'SG1.low' and 'master'
```

--------------------------------

### Sample iptables Stateful Firewall Script

Source: https://github.com/acassen/keepalived/blob/master/www/docs/Keepalived-LVS-NAT-Director-ProxyArp-Firewall-HOWTO.html

This is a sample bash script for configuring a stateful firewall using iptables. It is intended for use with an LVS-NAT director setup.

```bash
#!/bin/bash  

```

--------------------------------

### Multiline Parameter Definition Example

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Illustrates defining a multiline parameter using the backslash character to continue definitions across lines.

```keepalived
$INSTANCE= \
    vrrp_instance VI_${NUM} { \
        interface eth0.${NUM} \
        use_vmac vrrp${NUM}.1 \
        virtual_router_id 1 \
        @high priority 130 \
        @low priority 120 \
        advert_int 1 \
        virtual_ipaddress { \
            10.0.${NUM}.254/24 \
        } \
        track_script { \
            offset_instance_${NUM} \
        } \
    }

$NUM=0
$INSTANCE

$NUM=1
$INSTANCE
```

--------------------------------

### Sequence Block Example (Decimal)

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Generates multiple lines by iterating a variable through a defined range. Useful for generating IP addresses or other sequential parameters.

```keepalived
    ~SEQ(SUBNET, 0, 3) ip_address 10.0.${SUBNET}.1

    would produce:
        ip_address 10.0.0.1
        ip_address 10.0.1.1
        ip_address 10.0.2.1
        ip_address 10.0.3.1
```

--------------------------------

### Using ${_HASH} and ${_BANG} for Conditional Configuration

Source: https://github.com/acassen/keepalived/blob/master/www/docs/release-notes/Release-2.1.4.md

Demonstrates how to use ${_HASH} and ${_BANG} to conditionally enable or disable configuration lines. These are replaced by '#' and '!' respectively, allowing for commented-out sections without starting a comment.

```conf
$TEST=${_HASH}
$TEST test config
```

```conf
$TEST=
  or even
$TEST=#${_HASH}
```

--------------------------------

### Sequence Block Example (Hexadecimal)

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Generates multiple lines using hexadecimal representation for a variable. Particularly useful for IPv6 addresses.

```keepalived
    ~SEQx(SUBNET, 144, 16, 192) ip_address fe80::20:${SUBNET}:1
  or better
    ~SEQx(SUBNET, 0x90, 0x10, 0xc0) ip_address fe80::20:${SUBNET}:1

    would produce:
        ip_address fe80::20:90:1
        ip_address fe80::20:a0:1
        ip_address fe80::20:b0:1
        ip_address fe80::20:c0:1
```

--------------------------------

### ipvsadm Output

Source: https://github.com/acassen/keepalived/blob/master/www/docs/LVS-NAT-Keepalived-HOWTO.html

Shows the output of the 'ipvsadm' command after Keepalived has started, detailing the configured virtual server and its associated real server.

```bash
example-01:~ # ipvsadm
IP Virtual Server version 1.0.4 (size=65536)
Prot LocalAddress:Port Scheduler Flags
� -> RemoteAddress:Port���������� Forward Weight ActiveConn InActConn  
TCP� 192.168.1.11:ssh rr
� -> 10.20.40.10:ssh����������� Masq��� 1����� 0��������� 0
example-01:~ #
```

--------------------------------

### List Block Example (Single Variables)

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Generates lines by substituting values from a list into a variable. Useful for defining a set of specific parameters.

```keepalived
    ~LST(var, val1, val2, val3) ...

    ~LST(IP, 1, 2, 3, 4) ~LST(IP1, 5,6,7) 192.169.${IP}.${IP1}

produces:

    192.169.1.5
    192.169.1.6
    192.169.1.7
    192.169.2.5
    192.169.2.6
    192.169.2.7
    192.169.3.5
    192.169.3.6
    192.169.3.7
    192.169.4.5
    192.169.4.6
    192.169.4.7
```

--------------------------------

### Global Definitions Configuration

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/configuration-synopsis.md

Example of the global_defs block, including email notifications, SMTP server settings, router ID, multicast group for VRRP, and LVS sync daemon binding.

```keepalived
global_defs {
    notification_email {
        admin@example.com
    }
    notification_email_from keepalived@example.com
    smtp_server 127.0.0.1
    smtp_connect_timeout 30
    router_id LVS_MAIN
    # send an email on every state transition
    smtp_alert
    # multicast group used for VRRP adverts (default is RFC assigned)
    vrrp_mcast_group4 224.0.0.18
    # bind the IPVS synchronisation daemon to an interface and an instance
    lvs_sync_daemon eth0 VI_1
}
```

--------------------------------

### Configure Keepalived Build with Custom Prefix

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Configure the Keepalived build process to install into a specific directory using the --prefix option. This facilitates easier uninstallation and management of multiple versions.

```bash
./configure --prefix=/usr/local/keepalived-2.3.4
```

--------------------------------

### Keepalived SSL Server Health Check Configuration

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/case-study-healthcheck.md

Configure SSL_GET checkers for SSL server health checks. This example shows how to set up real servers with specific weights and failure detection parameters for SSL services.

```nginx
virtual_server 192.168.200.15 443 {
    delay_loop 20
    lb_algo rr
    lb_kind NAT
    persistence_timeout 360
    protocol TCP
    real_server 192.168.100.2 443 {
        weight 1
        SSL_GET
        {
            url {
                path /testurl/test.jsp
                digest ec90a42b99ea9a2f5ecbe213ac9eba03
            }
            url {
                path /testurl2/test.jsp
                digest 640205b7b0fc66c1ea91c463fac6334c
            }
            connect_timeout 3
            retry 3
            delay_before_retry 2
        }
    }
    real_server 192.168.100.3 443 {
        weight 1
        SSL_GET
        {
            url {
                path /testurl/test.jsp
                digest 640205b7b0fc66c1ea91c463fac6334c
            }
            connect_timeout 3
            retry 3
            delay_before_retry 2
        }
    }
}
```

--------------------------------

### Keepalived Debug Log Output

Source: https://github.com/acassen/keepalived/blob/master/www/docs/LVS-NAT-Keepalived-HOWTO.html

Example log messages when Keepalived is started with the -d flag, showing global definitions, SSL context, VRRP topology, and LVS topology.

```log
Sep 12 14:13:11 example-01 Keepalived: ------< Global definitions >------
Sep 12 14:13:11 example-01 Keepalived:� LVS ID = LVS_EXAMPLE_01
Sep 12 14:13:11 example-01 Keepalived:� Smtp server = 127.0.0.1
Sep 12 14:13:11 example-01 Keepalived:� Smtp server connection timeout = 100
Sep 12 14:13:11 example-01 Keepalived:� Email notification from = admins@example.com, fakepager@example.com
Sep 12 14:13:11 example-01 Keepalived:� Email notification = admins@example.com
Sep 12 14:13:11 example-01 Keepalived: ------< SSL definitions >------
Sep 12 14:13:11 example-01 Keepalived:� Using autogen SSL context
Sep 12 14:13:11 example-01 Keepalived: ------< VRRP Topology >------
Sep 12 14:13:11 example-01 Keepalived:� VRRP Instance = VI_1
Sep 12 14:13:11 example-01 Keepalived:��� Want State = MASTER
Sep 12 14:13:11 example-01 Keepalived:��� Runing on device = eth0
Sep 12 14:13:11 example-01 Keepalived:��� Virtual Router ID = 51
Sep 12 14:13:11 example-01 Keepalived:��� Priority = 150
Sep 12 14:13:11 example-01 Keepalived:��� Advert interval = 1sec
Sep 12 14:13:11 example-01 Keepalived:��� Preempt Active
Sep 12 14:13:11 example-01 Keepalived:��� Authentication type = SIMPLE_PASSWORD
Sep 12 14:13:11 example-01 Keepalived:��� Password = example
Sep 12 14:13:11 example-01 Keepalived:��� VIP count = 1
Sep 12 14:13:11 example-01 Keepalived:����� VIP1 = 192.168.1.11/32
Sep 12 14:13:11 example-01 Keepalived:� VRRP Instance = VI_GATEWAY
Sep 12 14:13:11 example-01 Keepalived:��� Want State = MASTER
Sep 12 14:13:11 example-01 Keepalived:��� Runing on device = eth1
Sep 12 14:13:11 example-01 Keepalived:��� Virtual Router ID = 52
Sep 12 14:13:11 example-01 Keepalived:��� Priority = 150
Sep 12 14:13:11 example-01 Keepalived:��� Advert interval = 1sec
Sep 12 14:13:11 example-01 Keepalived:��� Preempt Active
Sep 12 14:13:11 example-01 Keepalived:��� Authentication type = SIMPLE_PASSWORD
Sep 12 14:13:11 example-01 Keepalived:��� Password = example
Sep 12 14:13:11 example-01 Keepalived:��� VIP count = 1
Sep 12 14:13:11 example-01 Keepalived:����� VIP1 = 10.20.40.1/32
Sep 12 14:13:11 example-01 Keepalived: ------< VRRP Sync groups >------
Sep 12 14:13:11 example-01 Keepalived:� VRRP Sync Group = VG1, MASTER
Sep 12 14:13:11 example-01 Keepalived:��� monitor = VI_1
Sep 12 14:13:11 example-01 Keepalived:��� monitor = VI_GATEWAY
Sep 12 14:13:11 example-01 Keepalived: ------< LVS Topology >------
Sep 12 14:13:11 example-01 Keepalived:� System is compiled with LVS v1.0.4
Sep 12 14:13:11 example-01 Keepalived:� VIP = 192.168.1.11, VPORT = 22
Sep 12 14:13:11 example-01 Keepalived:��� delay_loop = 10, lb_algo = rr
Sep 12 14:13:11 example-01 Keepalived:��� protocol = TCP
Sep 12 14:13:11 example-01 Keepalived:��� lb_kind = NAT
Sep 12 14:13:11 example-01 Keepalived:��� RIP = 10.20.40.11, RPORT = 22, WEIGHT = 1
Sep 12 14:13:11 example-01 Keepalived: ------< Health checkers >------
Sep 12 14:13:11 example-01 Keepalived:� 10.20.40.11:22
Sep 12 14:13:11 example-01 Keepalived:��� Keepalive method = TCP_CHECK
Sep 12 14:13:11 example-01 Keepalived:��� Connection timeout = 10
Sep 12 14:13:11 example-01 Keepalived:��� Connection port = 22
```

--------------------------------

### Install Keepalived on Alpine

Source: https://github.com/acassen/keepalived/blob/master/www/docs/download.md

Use this command to install Keepalived on Alpine Linux.

```shell
sudo apk add keepalived
```

--------------------------------

### Install Keepalived on Arch Linux

Source: https://github.com/acassen/keepalived/blob/master/www/docs/download.md

Use this command to install Keepalived on Arch Linux.

```shell
sudo pacman -S keepalived
```

--------------------------------

### Script Execution with Parameters

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Illustrates how to pass parameters to scripts, including handling spaces within parameters using single quotes and using shell variables.

```bash
$SG_NAME=SG1
$INST=low
$USER=user
notify_master "/etc/keepalived/notify_event.sh ' spaces\x20f\x69le ' '\"s p a c e \"' ${SG_NAME}.${INST} master" $USER group
```

--------------------------------

### Build MkDocs Website Content

Source: https://github.com/acassen/keepalived/blob/master/www/README.md

Compiles the MkDocs website content into static files for deployment.

```bash
$ mkdocs build
```

--------------------------------

### Install Keepalived on Red Hat Enterprise Linux

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/installing.md

Use dnf (or yum) to install the keepalived package and its dependencies from the distribution's repositories.

```bash
dnf install keepalived
```

--------------------------------

### SSL GET Healthchecker Configuration

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Configure SSL GET health checks. This includes options for enabling Server Name Indicator (SNI) and complying with TLS protocol by sending a close_notify alert.

```keepalived
SSL_GET {
    enable_sni
    tls_compliant
}
```

--------------------------------

### HTTP GET Healthchecker Configuration

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Configure HTTP GET health checks for virtual servers. Supports specifying protocol version, recovery behavior, and detailed URL checks including path, digest, status codes, virtual host, regex matching, and SSL/TLS options.

```keepalived
HTTP_GET {
    http_protocol <PROTOCOL>
    fast_recovery [<BOOL>]
    url {
        path <STRING>
        digest <STRING>
        status_code <INTEGER|RANGE> [<INTEGER|RANGE>] ...
        virtualhost <STRING>
        regex <STRING>
        regex_no_match
        regex_options <OPTIONS>
        regex_stack <START> <MAX>
        regex_min_offset <OFFSET>
        regex_max_offset <OFFSET>
    }
}
```

--------------------------------

### Quoted String Example 1

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Demonstrates how whitespace is retained and quotes are removed when a string is enclosed in single quotes.

```text
'abcd" efg h jkl "mnop'
```

--------------------------------

### Combined List and Sequence Blocks

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Demonstrates combining list and sequence blocks to generate configurations with both predefined sets of values and sequential ranges.

```keepalived
    ~LST({IP, IP1}, {10,1},{20,4},{5,6},{12,8}) ~SEQ(IP2,168,2,172) 192.${IP2}.${IP}.${IP1}

produces:

    192.168.10.1
    192.170.10.1
    192.172.10.1
    192.168.20.4
    192.170.20.4
    192.172.20.4
    192.168.5.6
    192.170.5.6
    192.172.5.6
    192.168.12.8
    192.170.12.8
    192.172.12.8
```

--------------------------------

### Populate User-Defined Chains Message

Source: https://github.com/acassen/keepalived/blob/master/www/docs/Keepalived-LVS-NAT-Director-ProxyArp-Firewall-HOWTO.html

A simple echo command to indicate the start of populating user-defined chains during script execution.

```bash
echo " Populating User-Defined Chains..."

```

--------------------------------

### Multiple Sequence Blocks on One Line

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/keepalived-conf.md

Shows how to use multiple sequence blocks on a single line to generate a large number of configurations, like multiple VRRP instances.

```keepalived
    $VI4= \
    track_file offset_instance_4.${IF}.${NUM}.${ID} { \
        file "${_PWD}/679/track_files/4.${IF}.${NUM}.${ID}" \
        weight -100 \
    } \
    vrrp_instance vrrp4.${IF}.${NUM}.${ID} { \
        interface bond${IF}.${NUM} \
        use_vmac vrrp4.${IF}.${NUM}.${ID} \
        virtual_router_id ${ID} \
        priority 130 \
        virtual_ipaddress { \
            10.${IF}.${NUM}.${ID}/24 \
        } \
        track_file { \
            offset_instance_4.${IF}.${NUM}.${ID} \
        } \
    }

    ~SEQ(IF,0,7) ~SEQ(NUM,0,31) ~SEQ(ID,1,254) $VI4

    will produce 65024 vrrp instances with names from vrrp4.0.0.1 through to
    vrrp4.7.31.254.
```

--------------------------------

### Verify IPVS Configuration

Source: https://github.com/acassen/keepalived/blob/master/www/docs/documentation/user-guide/quick-start.md

Check that the virtual server and real servers have been programmed into the kernel's IPVS table.

```bash
# ipvsadm -Ln
```

--------------------------------

### Source SuSE Configuration

Source: https://github.com/acassen/keepalived/blob/master/www/docs/LVS-NAT-Keepalived-HOWTO.html

Loads configuration variables from the SuSE rc.config file if it exists. This is typically used in init scripts.

```bash
test -r /etc/rc.config && . /etc/rc.config
```