Check for duplicate IPs
arping -I eth1 20.20.187.194
ARPING 20.20.187.194
60 bytes from 00:50:56:a8:92:fa (20.20.187.194): index=0 time=487.776 usec
60 bytes from 00:50:56:9b:02:3a (20.20.187.194): index=1 time=718.761 usec=
-i interface
Use the specified interface.
reply is from 2 different mac address
How to disable SSH timeout?
To set the SSH keep alive option on the server:
1. Log in as root.
2. Edit the file at /etc/ssh/sshd_config.
3. Add this line to the file: ClientAliveInterval 60.
4. Save the file.
5. Restart sshd on the server.
Or
ssh -o ServerAliveInterval=0 root@10.90.137.118
To check how many ssh sessions are connected to device
netstat -tunp | grep 22
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 256 10.10.5.9a:22 10.65.92.231:62650 ESTABLISHED 11532/0
tcp 0 0 127.0.0.1:42294 127.0.0.1:5759 ESTABLISHED -
tcp 0 0 127.0.0.1:5759 127.0.0.1:42294 ESTABLISHED -
How to check available space on machine?
root@systest-runner:~[38200]# free -mh
total used free shared buff/cache available
Mem: 16038 15473 191 5 373 240
How to increase ssh timeout in Linux?
https://www.tecmint.com/increase-ssh-connection-timeout/
Disk space used by directories.
du -sh * | grep G
check which are top 5 storage occupying folders/files
du -hs * | sort -rh | head -5
Delete files older than 90 days
find . -mtime +$90 -type f -delete
To check size of directory:
du -h <dir>
Copy multiple files using scp
scp -r root@<ip>:/root/edges .
Check image is copied properly in tftp:
[root@iLnxRTR3 dbuild_02072015]# ls
cdisk.smp checksum
[root@iLnxRTR3 dbuild_02072015]# md5sum cdisk.smp
b9f2913fca176d4fbcc7a9dbc0673aaf cdisk.smp
[root@iLnxRTR3 dbuild_02072015]# cat checksum
b9f2913fca176d4fbcc7a9dbc0673aaf target/smp/cdisk.smp
[root@iLnxRTR3 dbuild_02072015]#
Create alias on terminal
vi ~/.bashrc
alias 1='telnet <ip> <port>'
For ssh alias:
alias n1="sshpass -p VMware1VMware! ssh root@<ip>"
source ~/.bashrc
Configure dns on Ubuntu
https://www.fosslinux.com/7631/how-to-install-and-configure-dns-on-ubuntu.htm
https://serverfault.com/questions/300438/bind9-failing-to-start
Enable tftp server:
https://graspingtech.com/ubuntu-tftp-server/
To find username of windows machine:
> echo %usermae%
Curl commands:
GET (-v for verbose) without any option by default is GET
curl -v http://localhost:8082/spring-rest/foos/9
POST (-d data, -H to modify content type )
curl -d '{"id":9,"name":"baeldung"}' -H 'Content-Type: application/json' http://localhost:8082/spring-rest/foos/new
PUT: (-x for put)
curl -d @request.json -H 'Content-Type: application/json'
-X PUT http://localhost:8082/spring-rest/foos/9
DELETE (-X for delete)
curl -X DELETE http://localhost:8082/spring-rest/foos/9
Authentication
curl --user baeldung:secretPassword http://example.com/
How to check DNS configuration on MAC:
NAWLEKHA-M-N1AJ:~ nawlekha$ scutil --dns
DNS configuration
resolver #1
nameserver[0] : 192.168.1.254
if_index : 5 (en0)
flags : Request A records
reach : 0x00020002 (Reachable,Directly Reachable Address)
How to flush dns in mac?
nawlekha$ sudo killall -INFO mDNSResponder
For cmake error - cmake: command not found
=========
sudo apt-get install build-essential cmake
Resolve Ipv6 ping issue :
https://askubuntu.com/questions/64500a/ipv6-connect-network-is-unreachable
Error: You don't have enough free space in /var/cache/apt/archives/' errors
============
https://www.marksayson.com/blog/investigating-space-issues-in-var-cache-apt-archives/
delete files from /var directory
To disable auto ipv6 on Linux:
=====================
sudo sysctl -w net.ipv6.conf.all.forwarding=1
ifconfig eth0.912 down
ifconfig eth0.912 up
Error: update stuck at : 0% [Connecting to us.archive.ubuntu.com (2001:67c:1562::15)]
============
It's better to disable the IPV6 before you update ## check this in below link
https://askubuntu.com/questions/574569/apt-get-stuck-at-0-connecting-to-us-archive-ubuntu-com
Error: If you are able to configure ipv6 address and seeing below error:
root@Ubuntu-Linux-2:~/sipp# ifconfig ens224.1670 inet6 add 172:52:1::2/64
SIOCSIFADDR: Permission denied
root@Ubuntu-Linux-2:~/sipp# /sbin/route -A inet6 add default gw 172:52:1::1
SIOCADDRT: No route to host
Follow same above link and enable ipv6
https://askubuntu.com/questions/574569/apt-get-stuck-at-0-connecting-to-us-archive-ubuntu-com
Create a Static ARP Table
If you know that the MAC address that corresponds to 192.16a.0.65 is 00:50:BA:a5:a5:CA, you could add a static ARP entry for it like this:
# arp -s 192.16a.0.65 00:50:ba:a5:a5:ca ## destination ip and corresponding mac
flush arp:
ip -s -s neigh flush all
delete arp for particular ip
arp -d 192.168.1.1
to check arp table
arp -n
To ping from specific interface;
ping -I ens33 9.9.9.8
Issue: Ubuntu is always taking ipv6 DNS server to reach internet and its not resolving.
root@tls-client:~# ping google.com
PING google.com(maa05s02-in-x0e.1e100.net (2404:6a00:4007:a0c::200e)) 56 data bytes
From 50:5:5::1 (50:5:5::1) icmp_seq=1 Destination unreachable: No route
From 50:5:5::1 (50:5:5::1) icmp_seq=2 Destination unreachable: No route
From 50:5:5::1 (50:5:5::1) icmp_seq=3 Destination unreachable: No route
https://askubuntu.com/questions/3229a/prefer-a-ipv4-dns-lookups-before-aaaaipv6-lookups
How to re-write pcap:
sudo tcprewrite -C -i input.cap -o output.cap
https://tcpreplay.appneta.com/wiki/tcprewrite
## how to create root user in Ubuntu
user@Ubuntu-Linux-1:~$ sudo su
[sudo] password for user:
root@Ubuntu-Linux-1:/home/user# passwd
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Proxy settings:
export https_proxy="https://proxy-wsa.esl.domain.com:80"
To copy everything present under directory:
cp -rf * /ws/nawlekha-bgl/automation/pyats/automation_package_bangalore_mc/.
How to copy using ftp from windows VM to mac
ftp user@10.104.10.113
ftp> ha
Hash mark printing on (1024 bytes/hash mark).
ftp> bi
200 Type set to I
ftp>
ftp> ls
ftp> get KP_RA_IPSEC_ASA.p12
ftp> bye
How to connect to website through port using ipv4 and ipv6?
http://1a0.1.1.10:90
http://[2001:dba:90::2]:90/
GET OS name
root@Ubuntu-Linux-1:~# cat /etc/os-release
NAME="Ubuntu"
How to restart dns service
[root@olinux1 named]# /etc/init.d/named restart
Convert ipv4 to ipv6 address:
3.3.5.245
in browser type [::3.3.5.245]
it will return ::303:5f5. use this address
Disable ipv6 autoconfig on Ubuntu
To check if IPv6 is enabled or disabled, from a terminal window:
$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6
0 means it’s enabled and 1 is disabled.
Network settings in Ubuntu:
sudo vi /etc/network/interfaces
How to convert ipv4 to ipv6
convert ipv4 to ipv6
60.1.1.10/24 to 60:1:1::10/96
Linux commands in DevOps: Must Know For Every DevOps Professional
https://www.edureka.co/blog/linux-commands-in-devops/
To check packet loss
ping 10.90.137.64 -c5
PING 10.90.137.64 (10.90.137.64): 56 data bytes
64 bytes from 10.90.137.64: icmp_seq=0 ttl=55 time=16.201 ms
Request timeout for icmp_seq 1
64 bytes from 10.90.137.64: icmp_seq=2 ttl=55 time=22.651 ms
Request timeout for icmp_seq 3
64 bytes from 10.90.137.64: icmp_seq=4 ttl=55 time=16.290 ms
--- 10.90.137.64 ping statistics ---
5 packets transmitted, 3 packets received, 40.0% packet loss
round-trip min/avg/max/stddev = 16.201/18.381/22.651/3.020 ms
## udpreplay is a lightweight alternative to tcpreplay for replaying UDP unicast and multicast streams from a pcap file
List IP tables
iptables --table nat --list
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