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systemrescue_as_a_router

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systemrescue_as_a_router [2026/06/20 17:18] – stevesystemrescue_as_a_router [2026/06/23 17:28] (current) – steve
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 ==== System Rescue as a router ==== ==== System Rescue as a router ====
-Use curl to get this script to a freshly booted machine running SystemRescue [[https://www.system-rescue.org/]] and use it as an emergency backup router.+Use curl to get this script to a freshly booted machine running SystemRescue [[https://www.system-rescue.org/]] and use it as an emergency backup router. This was set up in a VM and tested with SystemRescue 12.03.
  
 ^^%%curl -sL "https://wiki.cyli.org/doku.php?do=export_code&id=systemrescue_as_a_router&codeblock=0" | bash%%^^ ^^%%curl -sL "https://wiki.cyli.org/doku.php?do=export_code&id=systemrescue_as_a_router&codeblock=0" | bash%%^^
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 # The variables below are the only things that should need changing; # The variables below are the only things that should need changing;
  
-export ExtIF="enX0"                     # External Interface +export ExtIF="enX0"             # External Interface, connected to Internet 
-export IntIF="enX1"                     # Internal Interface +export IntIF="enX1"             # Internal Interface, connected to PCs 
-export Sub="31"                         # Subnet number +export Sub="192.168.11"         # Subnet number 
-export CIDR="/24"                       # Subnet mask +export CIDR="/24"               # Subnet mask 
-export IntIP="192.168.${Sub}.1"         # Internal interface address +export  IntIP="${Sub}.1"        # Internal interface address 
-export IntNet="192.168.${Sub}.0${CIDR}" # Internal Network +export IntNet="${Sub}.0${CIDR}" # Internal Network 
-export IntLow="192.168.${Sub}.50"       # Low IP lease +export IntLow="${Sub}.50"       # Low IP lease 
-export  IntHi="192.168.${Sub}.199"      # High IP lease +export  IntHi="${Sub}.199"      # High IP lease 
-export Dur="1h"                         # Lease duration +export Dur="1h"                 # Lease duration 
-export DNS1="8.8.8.8"                   # First DNS server +export DNS1="8.8.8.8"           # First DNS server 
-export DNS2="1.1.1.1"                   # Second DNS server+export DNS2="1.1.1.1"           # Second DNS server 
 +export Dom="cyli.org"           # Our domain
  
-# 1. Clean Dnsmasq Configuration 
 #    Replace the contents of your /etc/dnsmasq.conf file with the following  #    Replace the contents of your /etc/dnsmasq.conf file with the following 
- 
 mv /etc/dnsmasq.conf /etc/dnsmasq.orig mv /etc/dnsmasq.conf /etc/dnsmasq.orig
  
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 domain-needed domain-needed
 bogus-priv bogus-priv
-domain=local.lan+domain=${Dom}
 expand-hosts expand-hosts
  
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 # --- DHCP SETTINGS --- # --- DHCP SETTINGS ---
-# Lease range tailored to your ${IntNet} subnet+# Lease range for ${IntNet}
 dhcp-range=${IntLow},${IntHi},${Dur} dhcp-range=${IntLow},${IntHi},${Dur}
  
-# Explicitly pass this server's internal IP as the gateway+# Explicitly pass this VMs internal IP as the gateway
 dhcp-option=option:router,${IntIP} dhcp-option=option:router,${IntIP}
  
-# Announce this server as the authoritative DHCP source+# Announce this VM as the authoritative DHCP source
 dhcp-authoritative dhcp-authoritative
 EndOfFile EndOfFile
  
-# 2. Network Interface Alignment 
 #    Before starting the services, ensure your internal interface (${IntIF})  #    Before starting the services, ensure your internal interface (${IntIF}) 
 +#    is configured and up
 ip addr add ${IntIP}${CIDR} dev ${IntIF} ip addr add ${IntIP}${CIDR} dev ${IntIF}
 ip link set ${IntIF} up ip link set ${IntIF} up
  
-# 3. Bash Script to Flush Rules, Enable Routing, and NAT +#    Run this to completely wipe the firewall, enable system-level 
-#    Run this script to completely wipe the firewall, enable system-level +
 #    packet forwarding, and route internal client traffic out to the  #    packet forwarding, and route internal client traffic out to the 
 #    internet through ${ExtIF}. #    internet through ${ExtIF}.
-#     1. Enable IPv4 packet forwarding in the Linux kernel+#      Enable IPv4 packet forwarding in the Linux kernel
 sysctl -w net.ipv4.ip_forward=1 sysctl -w net.ipv4.ip_forward=1
 echo "net.ipv4.ip_forward=1" | tee -a /etc/sysctl.conf echo "net.ipv4.ip_forward=1" | tee -a /etc/sysctl.conf
  
-#     2. Set default policies to ACCEPT everything temporarily+#      Set default policies to ACCEPT everything temporarily
 iptables -P INPUT ACCEPT iptables -P INPUT ACCEPT
 iptables -P FORWARD ACCEPT iptables -P FORWARD ACCEPT
 iptables -P OUTPUT ACCEPT iptables -P OUTPUT ACCEPT
  
-#     3. Flush all rules from all tables (Filter, NAT, Mangle)+#      Flush all rules from all tables (Filter, NAT, Mangle)
 iptables -F iptables -F
 iptables -t nat -F iptables -t nat -F
 iptables -t mangle -F iptables -t mangle -F
  
-#     4. Delete all custom user-defined chains+#      Delete all custom user-defined chains
 iptables -X iptables -X
 iptables -t nat -X iptables -t nat -X
 iptables -t mangle -X iptables -t mangle -X
  
-#     5. Reset all packet and byte counters back to zero+#      Reset all packet and byte counters back to zero
 iptables -Z iptables -Z
  
-#     6. Configure NAT / Masquerade out of the external interface+#      Configure NAT / Masquerade out of the external interface
 iptables -t nat -A POSTROUTING -o ${ExtIF} -j MASQUERADE iptables -t nat -A POSTROUTING -o ${ExtIF} -j MASQUERADE
  
-#     7. Forward traffic from internal network out to the internet+#      Forward traffic from internal network out to the internet
 iptables -A FORWARD -i ${IntIF} -o ${ExtIF} -j ACCEPT iptables -A FORWARD -i ${IntIF} -o ${ExtIF} -j ACCEPT
 iptables -A FORWARD -i ${ExtIF} -o ${IntIF} -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -i ${ExtIF} -o ${IntIF} -m state --state RELATED,ESTABLISHED -j ACCEPT
  
  
-## Restarting the Clean Infrastructure 
 #  Wipe out any runtime artifacts from old setups and fire up the new router configuration #  Wipe out any runtime artifacts from old setups and fire up the new router configuration
 #  Clear any stuck active leases #  Clear any stuck active leases
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 systemctl restart dnsmasq systemctl restart dnsmasq
 </code> </code>
 +{{ :scripts:routertestcommand_prompt.png?nolink |}}
systemrescue_as_a_router.1781975928.txt.gz · Last modified: by steve