How to enable SSH service on Fedora Linux?

How to enable SSH service on Fedora Linux? By default, it seems ssh is not enabled.

Fedora may not have sshd service installed/enabled by default. You will need to install and configure it by yourself. The following instructions is for Fedora 22 as an example.

First, install the sshd server by

# dnf install openssh-server

Then, start the sshd service and make it automatically start next time you boot by

# systemctl start sshd.service
# systemctl enable sshd.service

Last, enable external connection to the port 22 (the default one) by configuring the firewall you are using.

Note: you may not need additional configurations if 22 is already opened.

If you are using firwalld, you may use the firewall-config tool (install it by dnf install firwall-config if you haven’t it).

Some further readings that you may find useful:

How to enable iptables on Fedora 20 http://ask.systutorials.com/694/how-to-enable-iptables-on-fedora-20

Basic iptables configuration for Linux http://ask.systutorials.com/1381/basic-iptables-configuration-for-linux

How to use iptables to limit rates new SSH incoming connections from each IP on Linux http://ask.systutorials.com/1378/iptables-limit-rates-incoming-connections-from-each-linux

How to log connections hitting certain rules in iptables on Linux http://ask.systutorials.com/1386/how-log-connections-hitting-certain-rules-iptables-on-linux

Answered by Eric Z Ma.

A simple destop firewall:

http://www.cyberciti.biz/faq/linux-detect-port-scan-attacks/

copy paste from #! until the end (including exit 0) and put it in a file ending on sh (bash script).Make it executable.Don’t forget to check the name of your network interface with ifconfig.

#!/bin/bash
IPT="/sbin/iptables"
 
echo "Starting IPv4 Wall..."
$IPT -F
$IPT -X
$IPT -t nat -F
$IPT -t nat -X
$IPT -t mangle -F
$IPT -t mangle -X
modprobe ip_conntrack
 
BADIPS=$(egrep -v -E "^#|^$" /root/scripts/blocked.fw)
PUB_IF="eth0"
 
#unlimited 
$IPT -A INPUT -i lo -j ACCEPT
$IPT -A OUTPUT -o lo -j ACCEPT
 
# DROP all incomming traffic
$IPT -P INPUT DROP
$IPT -P OUTPUT DROP
$IPT -P FORWARD DROP
 
# block all bad ips
for ip in $BADIPS
do
    $IPT -A INPUT -s $ip -j DROP
    $IPT -A OUTPUT -d $ip -j DROP
done
 
# sync
$IPT -A INPUT -i ${PUB_IF} -p tcp ! --syn -m state --state NEW  -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "Drop Syn"
 
 
$IPT -A INPUT -i ${PUB_IF} -p tcp ! --syn -m state --state NEW -j DROP
 
# Fragments
$IPT -A INPUT -i ${PUB_IF} -f  -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "Fragments Packets"
$IPT -A INPUT -i ${PUB_IF} -f -j DROP
 
 
# block bad stuff
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL ALL -j DROP
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL NONE -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "NULL Packets"
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL NONE -j DROP # NULL packets
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,FIN SYN,FIN -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "XMAS Packets"
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP #XMAS
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags FIN,ACK FIN -m limit --limit 5/m --limit-burst 7 -j LOG --log-level 4 --log-prefix "Fin Packets Scan"
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags FIN,ACK FIN -j DROP # FIN packet scans
 
$IPT  -A INPUT -i ${PUB_IF} -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
 
 
# Allow full outgoing connection but no incomming stuff
$IPT -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -o eth0 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
 
# allow ssh only
$IPT -A INPUT -p tcp --destination-port 22 -j ACCEPT
$IPT -A OUTPUT -p tcp --sport 22 -j ACCEPT
 
# allow incoming ICMP ping pong stuff
$IPT -A INPUT -p icmp --icmp-type 8 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -p icmp --icmp-type 0 -m state --state ESTABLISHED,RELATED -j ACCEPT
 
# No smb/windows sharing packets - too much logging
$IPT -A INPUT -p tcp -i eth0 --dport 137:139 -j REJECT
$IPT -A INPUT -p udp -i eth0 --dport 137:139 -j REJECT
 
# Log everything else
# *** Required for psad ****
$IPT -A INPUT -j LOG
$IPT -A FORWARD -j LOG
$IPT -A INPUT -j DROP
 
# Start ipv6 firewall
# echo "Starting IPv6 Wall..."
#/root/scripts/start6.fw
 
exit 0

Eric Z Ma

Eric is a father and systems guy. Eric is interested in building high-performance and scalable distributed systems and related technologies. The views or opinions expressed here are solely Eric's own and do not necessarily represent those of any third parties.

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