ping / nslookup / dig

Check connectivity (press Ctrl+C to stop).

ping hostname_or_ip

Send ping a specified number of times.

ping -c count hostname

Look up the IP address of a domain (nslookup).

nslookup domain

Look up DNS records in detail (dig).

dig domain

Look up a specific record type.

dig domain record_type

Query a specific DNS server.

dig @dns_server domain

Command / Option	Description
ping host	Sends ICMP packets to check connectivity.
ping -c count	Specifies the number of packets to send.
ping -i seconds	Specifies the interval between packets in seconds.
ping -t TTL	Specifies the TTL value.
nslookup domain	Looks up the A record (IP address) for a domain.
nslookup -type=MX domain	Looks up the MX record (mail server) for a domain.
dig domain	Looks up DNS records in detail (defaults to A record).
dig domain MX	Looks up the MX record for a domain.
dig domain NS	Looks up the NS record (name servers) for a domain.
dig domain TXT	Looks up TXT records (SPF, DKIM, etc.) for a domain.
dig +short domain	Outputs only the IP address in a concise format.
dig @8.8.8.8 domain	Queries Google's DNS server.
ss -tuln	Displays open ports and listening services.
netstat -tuln	Displays a list of ports, similar to ss (for older systems).

Send ping exactly 5 times and check response times.

ping -c 5 google.com
PING google.com (142.250.196.46): 56 data bytes
64 bytes from 142.250.196.46: icmp_seq=0 ttl=118 time=5.123 ms
64 bytes from 142.250.196.46: icmp_seq=1 ttl=118 time=4.987 ms
64 bytes from 142.250.196.46: icmp_seq=2 ttl=118 time=5.234 ms
64 bytes from 142.250.196.46: icmp_seq=3 ttl=118 time=5.001 ms
64 bytes from 142.250.196.46: icmp_seq=4 ttl=118 time=4.876 ms

--- google.com ping statistics ---
5 packets transmitted, 5 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 4.876/5.044/5.234/0.122 ms

Use ping in a script to monitor server availability. The -c 1 flag sends only one packet, and -W 2 sets a 2-second timeout.

health_check.sh

if ping -c 1 -W 2 192.168.1.1 > /dev/null 2>&1; then
    echo "Server is running"
else
    echo "Server is not responding"
fi

bash health_check.sh
Server is running

You can also enter an if statement directly in the terminal. After pressing Enter following then, a > prompt appears to indicate more input is expected. Enter fi to execute.

if ping -c 1 -W 2 192.168.1.1 > /dev/null 2>&1; then
    echo "Server is running"
else
    echo "Server is not responding"
fi
Server is running

Retrieve only the A record (IP address) for a domain in a simple format.

dig +short example.com
93.184.216.34

Check the MX record (mail server configuration).

dig example.com MX +short
10 mail.example.com.
20 mail2.example.com.

Check the TXT record (SPF configuration).

dig example.com TXT +short
"v=spf1 include:_spf.google.com ~all"

Resolve a domain using Google DNS (8.8.8.8). Useful when you want to bypass your ISP's DNS.

dig @8.8.8.8 example.com +short
93.184.216.34

Perform a reverse lookup to find the domain name for an IP address.

dig -x 93.184.216.34 +short
example.com.

Check the MX record using nslookup.

nslookup -type=MX gmail.com
Server:		8.8.8.8
Address:	8.8.8.8#53

Non-authoritative answer:
gmail.com	mail exchanger = 5 gmail-smtp-in.l.google.com.
gmail.com	mail exchanger = 10 alt1.gmail-smtp-in.l.google.com.

Check open ports on the system.

ss -tuln
Netid  State   Recv-Q  Send-Q   Local Address:Port   Peer Address:Port
tcp    LISTEN  0       128      0.0.0.0:22            0.0.0.0:*
tcp    LISTEN  0       128      0.0.0.0:80            0.0.0.0:*
tcp    LISTEN  0       128      0.0.0.0:443           0.0.0.0:*

When using ping in scripts for server health monitoring, the standard approach is to combine -c 1 (send only once) with -W 2 (2-second timeout) for fast response detection.

For DNS investigation, use dig +short domain for a quick IP lookup, and dig (without options) for full details. nslookup is an older tool but remains widely used because its interactive mode is easy to work with.