- Check if a host is reachable and a port is open
telnet <host> <port>
- Check routing to host
ip route get 172.31.132.29
172.31.132.29 via 10.1.19.254 dev wlp5s0 src 10.1.17.31 uid 1000
cache
Port forwarding example in ~/.ssh/config:
Host voyager-prod-bastion*
Hostname voyager-prod-bastion.aws.zedconnect.com
User ec2-user
ForwardAgent yes
AddKeysToAgent yes
IdentityFile ~/.ssh/key.pem
IdentitiesOnly yes
LocalForward localhost:9993 voyager-db.prod.aws.zedconnect.com:3306
Curl is a "CLI browser".
GET examples:
curl -s \
-H "DevAuthorization: fleetadmin|fleetadmin_dev_1" \
"https://voyager-core.dev.internal.zedconnect.com/"
curl --insecure \
-H "Authorization: Bearer <token>" \
https://eagle.wkda-test.com/employee/ \
| jq -r
where jq -r to prettyprint json.
POST request with Parameters:
curl --data "firstName=John&lastName=Doe" https://yourdomain.com/info.php
POST with request body in the given file and specified headers:
curl -s -XPOST -H "DevAuthorization: fleetadmin|fleetadmin_dev_1" -H "Content-Type: application/json" "https://voyager-core.dev.internal.zedconnect.com/drivers/1/reports" [email protected]
Download the file (may use wget instead):
curl -o archive.zip https://domain.com/file.zip
Or with -O for saving files with the same names as on the remote server:
curl -O https://domain.com/file.zip
Query HTTP Headers:
curl -I www.tecmint.com
Use a Proxy:
curl -x proxy.yourdomain.com:8080 -U user:password -O http://yourdomain.com/yourfile.tar.gz,
where you can skip -U user:password if proxy does not require auth.
Wget retrieves content from web servers. Wget can continue iterrupted downloads, download multiple URLs or multiple files from URL, download with HTTP auth, work like a spider and other stuff. But still curl can do almost everthing that wget does and more
Download a single file from the Internet:
wget http://example.com/file.iso
Download a file but save it locally under a different name:
wget ‐‐output-document=filename.html example.com
SCP is a "secure copy", it allows files to be copied to, from, or between different hosts. It uses ssh for data transfer and provides the same authentication and same level of security as ssh.
Copy file from remote to local:
scp [email protected]:foobar.txt /some/local/directory
Copy file from local to remote:
scp foobar.txt [email protected]:/some/remote/directory
To check connectivity to the host:
ping <host>
❗ The ping command does not use TCP or UDP. It uses ICMP.
To check IPs of the routers on the route and number of hops.
Can be used to locate where the loss of data occurs, and probably the node is down.
Can be used to locate slow nodes.
traceroute <ip address>
Using telnet to test open TCP ports:
telnet <domainname or ip> [port]
iproute2 and net-tools packages.
iproute2 package now replaces deprecated net-tools.
New ip [opts] <object> <command> is equivalent to old ifconfig.
The output of ifconfig or ip -c link show shows the list of network interfaces like:
loloopbacketh0orenpXsYethernetwlan0orwlpXsYwirelessvmnetVM's interface working in bridge mode or NAT modebr0- bridgevirbr0- "Virtual Bridge 0" interface is used for NAT (Network Address Translation)docker0- docker interface
ip command objects can be:
addressto show addresses assigned to network interfaceslinkto show network interfaces- others
To check assigned IPs, -4 = IPv4 only, a = address, -c = color output:
ip -4 -c a
Bring up or down network interface eth0:
ip link set eth0 [up|down]
ifconfig eth0 [up|down]
Посмотреть таблицу маршрутизации:
ip route
...
default via 192.168.0.1 dev wlp2s0 proto dhcp metric 600
169.254.0.0/16 dev wlp2s0 scope link metric 1000
192.168.0.0/24 dev wlp2s0 proto kernel scope link src 192.168.0.17 metric 600
This is similar to route -n or netstat -rn which have the following output:
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 wlp2s0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 wlp2s0
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 wlp2s0
Where flags G = gateway (router), U = route is up, H = host route (exact IP match).
First row means route all packages from all hosts to 192.168.0.1.
Second and third tell route all packages from 169.245.0.0/16 and 192.168.0.0/24 directly on to wlp2s0 interface.
Netstat command displays various network related information
Show gateway info, subnet mask & interface it is going through:
netstat -rnv
Show all ports that are listening currently:
netstat -l
Show all [tcp, udp] ports:
netstat -a[t,u]
Show statistics for each protocol:
netstat -s
netstat -p will add the “PID/Program Name” to the netstat output. This is useful to identify which program is running on a particular port:
netstat -pt
...
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 1 0 ramesh-laptop.loc:47212 192.168.185.75:www CLOSE_WAIT 2109/firefox
tcp 0 0 ramesh-laptop.loc:52750 lax:www ESTABLISHED 2109/firefox
Find out on which port a program is running, for example ssh:
netstat -ap | grep ssh
Find out which process is using a particular port:
netstat -an | grep ':80'
Show the list of network interfaces (similar to ifconfig):
netstat -ie
Nmcli is a cli tool for controlling NetworkManager.
It is used to create, display, edit, delete, activate, and deactivate network connections, as well as control and display network device status.
Show the list of network interfaces:
nmcli device
Show info on specific interface:
nmcli device show <interface>
Show connections active/inactive:
nmcli connection
Netcat or nc is a networking utility for debugging and investigating the network.
This utility can be used for creating TCP/UDP connections and investigating them:
nc -l 2389 // nc is now listening on port 2389 for a connection
nc localhost 2389 // connecting
There should now be a connection between the ports. Anything typed at the second console will be concatenated to the first, and vice-versa.
Examples of data transfer:
nc -l 1234 > filename.out
nc host.example.com 1234 < filename.in
Port scanning:
nc -zv host.example.com 20-30
Connection to host.example.com 22 port [tcp/ssh] succeeded!
Connection to host.example.com 25 port [tcp/smtp] succeeded!
Cloning user home directory over net. Users should have the same UID, GID. Check with id and modify with:
sudo usermod --uid 1234 your-username
sudo groupmod --gid 1234 your-username
On source machine:
tar cz -C/home $(whoami) | nc -l -p 8888 -w 10 -vv
where -l= listen, -p = on port, -w = wait for secs, -vv = verbose.
On target machine:
nc -vv <ip_address_of_source_machine> 8888|tar xzp -C/home\
Tcpdump traces every single transaction leaving/coming.
To dump traffic of a specified interface:
tcpdump -i wlp2s0
Ethtool shows info about network interface (link up/down, supported modes, speed, etc):
ethtool enp1s0
Nslookup resolves hostname to ip and vice versa.
nslookup <hostname> shows local DNS and IPs for resolved hostname.
Dig does practically the same: dig <hostname>
Package name - httpd
Service:
systemctl enable httpd
systemctl restart httpd
Files:
etc/http/conf/httpd.conf- configvar/www/html/index.html- main page`var/log/httpd