Password Entering dialogue box would not show up in Outlook
Problem: After changing password, open Outlook, it is not connected the exchange server. 'Missing password' shows up at bottom right corner, but the password entering box would not show up.
Cause: You are sharing screen in Zoom meeting.
Solution: Stop sharing screen, then the password entering box wil l show up.
Ubuntu (20.04) Linux Network Configuration
https://ubuntu.com/server/docs/network-configuration
Ubuntu ships with a number of graphical utilities to configure your network devices. This document is geared toward server administrators and will focus on managing your network on the command line.
Ethernet interfaces are identified by the system using predictable network interface names. These names can appear as eno1 or enp0s25. However, in some cases an interface may still use the kernel eth# style of naming.
To quickly identify all available Ethernet interfaces, you can use the ip command as shown below.
ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether 00:16:3e:e2:52:42 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet 10.102.66.200/24 brd 10.102.66.255 scope global dynamic eth0
valid_lft 3257sec preferred_lft 3257sec
inet6 fe80::216:3eff:fee2:5242/64 scope link
valid_lft forever preferred_lft forever
Another application that can help identify all network interfaces available to your system is the lshw command. This command provides greater details around the hardware capabilities of specific adapters. In the example below, lshw shows a single Ethernet interface with the logical name of eth0 along with bus information, driver details and all supported capabilities.
sudo lshw -class network
*-network
description: Ethernet interface
product: MT26448 [ConnectX EN 10GigE, PCIe 2.0 5GT/s]
vendor: Mellanox Technologies
physical id: 0
bus info: pci@0004:01:00.0
logical name: eth4
version: b0
serial: e4:1d:2d:67:83:56
slot: U78CB.001.WZS09KB-P1-C6-T1
size: 10Gbit/s
capacity: 10Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm vpd msix pciexpress bus_master cap_list ethernet physical fibre 10000bt-fd
configuration: autonegotiation=off broadcast=yes driver=mlx4_en driverversion=4.0-0 duplex=full firmware=2.9.1326 ip=192.168.1.1 latency=0 link=yes multicast=yes port=fibre speed=10Gbit/s
resources: iomemory:24000-23fff irq:481 memory:3fe200000000-3fe2000fffff memory:240000000000-240007ffffff
Interface logical names can also be configured via a netplan configuration. If you would like control which interface receives a particular logical name use the match and set-name keys. The match key is used to find an adapter based on some criteria like MAC address, driver, etc. Then the set-name key can be used to change the device to the desired logial name.
network:
version: 2
renderer: networkd
ethernets:
eth_lan0:
dhcp4: true
match:
macaddress: 00:11:22:33:44:55
set-name: eth_lan0
ethtool is a program that displays and changes Ethernet card settings such as auto-negotiation, port speed, duplex mode, and Wake-on-LAN. The following is an example of how to view supported features and configured settings of an Ethernet interface.
sudo ethtool eth4
Settings for eth4:
Supported ports: [ FIBRE ]
Supported link modes: 10000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: No
Supported FEC modes: Not reported
Advertised link modes: 10000baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: No
Advertised FEC modes: Not reported
Speed: 10000Mb/s
Duplex: Full
Port: FIBRE
PHYAD: 0
Transceiver: internal
Auto-negotiation: off
Supports Wake-on: d
Wake-on: d
Current message level: 0x00000014 (20)
link ifdown
Link detected: yes
The following section describes the process of configuring your systems IP address and default gateway needed for communicating on a local area network and the Internet.
For temporary network configurations, you can use the ip command which is also found on most other GNU/Linux operating systems. The ip command allows you to configure settings which take effect immediately, however they are not persistent and will be lost after a reboot.
To temporarily configure an IP address, you can use the ip command in the following manner. Modify the IP address and subnet mask to match your network requirements.
sudo ip addr add 10.102.66.200/24 dev enp0s25
The ip can then be used to set the link up or down.
ip link set dev enp0s25 up
ip link set dev enp0s25 down
To verify the IP address configuration of enp0s25, you can use the ip command in the following manner.
ip address show dev enp0s25
10: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether 00:16:3e:e2:52:42 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet 10.102.66.200/24 brd 10.102.66.255 scope global dynamic eth0
valid_lft 2857sec preferred_lft 2857sec
inet6 fe80::216:3eff:fee2:5242/64 scope link
valid_lft forever preferred_lft forever6
To configure a default gateway, you can use the ip command in the following manner. Modify the default gateway address to match your network requirements.
sudo ip route add default via 10.102.66.1
To verify your default gateway configuration, you can use the ip command in the following manner.
ip route show
default via 10.102.66.1 dev eth0 proto dhcp src 10.102.66.200 metric 100
10.102.66.0/24 dev eth0 proto kernel scope link src 10.102.66.200
10.102.66.1 dev eth0 proto dhcp scope link src 10.102.66.200 metric 100
If you require DNS for your temporary network configuration, you can add DNS server IP addresses in the file /etc/resolv.conf. In general, editing /etc/resolv.conf
directly is not recommanded, but this is a temporary and non-persistent
configuration. The example below shows how to enter two DNS servers to /etc/resolv.conf,
which should be changed to servers appropriate for your network. A more
lengthy description of the proper persistent way to do DNS client
configuration is in a following section.
nameserver 8.8.8.8
nameserver 8.8.4.4
If you no longer need this configuration and wish to purge all IP configuration from an interface, you can use the ip command with the flush option as shown below.
ip addr flush eth0
Note
Flushing the IP configuration using the ip command does not clear the contents of
/etc/resolv.conf. You must remove or modify those entries manually, or re-boot which should also cause/etc/resolv.conf, which is a symlink to/run/systemd/resolve/stub-resolv.conf, to be re-written.
To configure your server to use DHCP for dynamic address assignment, create a netplan configuration in the file /etc/netplan/99_config.yaml. The example below assumes you are configuring your first Ethernet interface identified as enp3s0.
network:
version: 2
renderer: networkd
ethernets:
enp3s0:
dhcp4: true
The configuration can then be applied using the netplan command.
sudo netplan apply
To configure your system to use static address assignment, create a netplan configuration in the file /etc/netplan/99_config.yaml. The example below assumes you are configuring your first Ethernet interface identified as eth0. Change the addresses, gateway4, and nameservers values to meet the requirements of your network.
network:
version: 2
renderer: networkd
ethernets:
eth0:
addresses:
- 10.10.10.2/24
gateway4: 10.10.10.1
nameservers:
search: [mydomain, otherdomain]
addresses: [10.10.10.1, 1.1.1.1]
The configuration can then be applied using the netplan command.
sudo netplan apply
The loopback interface is identified by the system as lo and has a default IP address of 127.0.0.1. It can be viewed using the ip command.
ip address show lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
Name resolution as it relates to IP networking is the process of mapping IP addresses to hostnames, making it easier to identify resources on a network. The following section will explain how to properly configure your system for name resolution using DNS and static hostname records.
Traditionally, the file /etc/resolv.conf was a static
configuration file that rarely needed to be changed or automatically
changed via DCHP client hooks. Systemd-resolved handles name server
configuration, and it should be interacted with through the systemd-resolve command. Netplan configures systemd-resolved to generate a list of nameservers and domains to put in /etc/resolv.conf, which is a symlink:
/etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf
To configure the resolver, add the IP addresses of the nameservers that are appropriate for your network to the netplan configuration file. You can also add an optional DNS suffix search-lists to match your network domain names. The resulting file might look like the following:
network:
version: 2
renderer: networkd
ethernets:
enp0s25:
addresses:
- 192.168.0.100/24
gateway4: 192.168.0.1
nameservers:
search: [mydomain, otherdomain]
addresses: [1.1.1.1, 8.8.8.8, 4.4.4.4]
The search option can also be used with multiple domain
names so that DNS queries will be appended in the order in which they
are entered. For example, your network may have multiple sub-domains to
search; a parent domain of example.com, and two sub-domains, sales.example.com and dev.example.com.
If you have multiple domains you wish to search, your configuration might look like the following:
network:
version: 2
renderer: networkd
ethernets:
enp0s25:
addresses:
- 192.168.0.100/24
gateway4: 192.168.0.1
nameservers:
search: [example.com, sales.example.com, dev.example.com]
addresses: [1.1.1.1, 8.8.8.8, 4.4.4.4]
If you try to ping a host with the name of server1, your system will automatically query DNS for its Fully Qualified Domain Name (FQDN) in the following order:
server1.example.com
server1.sales.example.com
server1.dev.example.com
If no matches are found, the DNS server will provide a result of notfound and the DNS query will fail.
Static hostnames are locally defined hostname-to-IP mappings located in the file /etc/hosts. Entries in the hosts
file will have precedence over DNS by default. This means that if your
system tries to resolve a hostname and it matches an entry in
/etc/hosts, it will not attempt to look up the record in DNS. In some
configurations, especially when Internet access is not required, servers
that communicate with a limited number of resources can be conveniently
set to use static hostnames instead of DNS.
The following is an example of a hosts file where a
number of local servers have been identified by simple hostnames,
aliases and their equivalent Fully Qualified Domain Names (FQDN’s).
127.0.0.1 localhost
127.0.1.1 ubuntu-server
10.0.0.11 server1 server1.example.com vpn
10.0.0.12 server2 server2.example.com mail
10.0.0.13 server3 server3.example.com www
10.0.0.14 server4 server4.example.com file
Note
In the above example, notice that each of the servers have been given aliases in addition to their proper names and FQDN’s. Server1 has been mapped to the name vpn, server2 is referred to as mail, server3 as www, and server4 as file.
The order in which your system selects a method of resolving
hostnames to IP addresses is controlled by the Name Service Switch (NSS)
configuration file /etc/nsswitch.conf. As mentioned in the previous section, typically static hostnames defined in the systems /etc/hosts
file have precedence over names resolved from DNS. The following is an
example of the line responsible for this order of hostname lookups in
the file /etc/nsswitch.conf.
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
files first tries to resolve static hostnames located in /etc/hosts.
mdns4_minimal attempts to resolve the name using Multicast DNS.
[NOTFOUND=return] means that any response of notfound by the preceding mdns4_minimal process should be treated as authoritative and that the system should not try to continue hunting for an answer.
dns represents a legacy unicast DNS query.
mdns4 represents a Multicast DNS query.
To modify the order of the above mentioned name resolution methods, you can simply change the hosts:
string to the value of your choosing. For example, if you prefer to use
legacy Unicast DNS versus Multicast DNS, you can change the string in /etc/nsswitch.conf as shown below.
hosts: files dns [NOTFOUND=return] mdns4_minimal mdns4
Bridging multiple interfaces is a more advanced configuration, but is very useful in multiple scenarios. One scenario is setting up a bridge with multiple network interfaces, then using a firewall to filter traffic between two network segments. Another scenario is using bridge on a system with one interface to allow virtual machines direct access to the outside network. The following example covers the latter scenario.
Configure the bridge by editing your netplan configuration found in /etc/netplan/:
network:
version: 2
renderer: networkd
ethernets:
enp3s0:
dhcp4: no
bridges:
br0:
dhcp4: yes
interfaces:
- enp3s0
Note
Enter the appropriate values for your physical interface and network.
Now apply the configuration to enable the bridge:
sudo netplan apply
The new bridge interface should now be up and running. The brctl
provides useful information about the state of the bridge, controls
which interfaces are part of the bridge, etc. See man brctl for more information.
Users of the former ifupdown may be familiar with using hook scripts (e.g pre-up, post-up, etc.) in their interfaces file. Netplan configuration does not currently support hook scripts in its configuration definition.
Instead to achieve this functionality with the networkd renderer, users can use networkd-dispatcher.
The package provides users and packages hook points when specific
network states are reached to aid in reacting to network state.
Note: If not on Ubuntu Server, but Desktop the network is driven by Network Manager - in that case you’d need NM Dispatcher scripts instead.
The Netplan FAQ has a great table that compares event timings between ifupdown/systemd-networkd/network-manager
It is important to be aware that those hooks run asychronous; that is they will not block transition into another state.
The Netplan FAQ also has an example on converting an old ifupdown hook to networkd-dispatcher.
The Ubuntu Wiki Network page has links to articles covering more advanced network configuration.
The netplan website has additional examples and documentation.
The netplan man page has more information on netplan.
The systemd-resolved man page has more information on systemd-resolved service.
For more information on bridging see the netplan.io examples page and the Linux Foundation’s Networking-Bridge page.
Want IP of Ubuntu WSL 2 be in the same network of host Window system
https://github.com/microsoft/WSL/issues/4150#issuecomment-504209723
https://stackoverflow.com/questions/4487328/match-two-strings-in-one-line-with-grep
You can use
grep -inH 'string1' filename | grep -inH 'string2'
Or
grep -inH 'string1.*string2\|string2.*string1' filename
sshd: no hostkeys available -- exiting
https://www.garron.me/en/linux/sshd-no-hostkeys-available-exiting.html
I only needed to run
ssh-keygen -A
In the /etc/ssh/ folder, and the start the server
/etc/init.d/ssh start
What if ssh would not start?
This issue is caused by a bad configuration of /etc/ssh/sshd_config file. When the service try to launch it does not recognize every fields of this configuration file. In order to solve this issue, you must use the tool
/usr/sbin/sshd -T
In case /etc/ssh/sshd_config was wrong, this would show wrong parameters with lines.
You must correct this issues and then restart the service:
/etc/init.d/ssh restart
Accessing network applications between windows and wsl linux ubuntu
https://docs.microsoft.com/en-us/windows/wsl/compare-versions
Accessing Linux networking apps from Windows (localhost)
Accessing Windows networking apps from Linux (host IP)
Connecting via remote IP addresses
Accessing a WSL 2 distribution from your local area network (LAN)
IPv6 access
How to start a service on ubuntu?
sudo service ssh start
And one could reasonably wonder, "how would you know that the service name was 'ssh'?" You can see them using
service --status-all
How to Delete Lines in Vim / Vi
https://linuxize.com/post/vim-delete-line/
Deleting a Line
The command to delete a line in Vim is dd .
Below are step-by-step instructions to delete a line:
Press the Esc key to go to normal mode.
Place the cursor on the line you want to delete.
Type dd and hit Enter to remove the line.
Pressing dd multiple times will delete multiple lines.
Deleting Multiple Lines
To delete multiple lines at once, prepend the dd command with the number of lines to be deleted. For example, to delete five lines you would do the following:
Press the Esc key to go to normal mode.
Place the cursor on the first line you want to delete.
Type 5dd and hit Enter to delete the next five lines.
Delete a range of lines
The syntax for deleting a range of lines is as follows:
:[start],[end]d
For example, to delete lines starting from 3 to 5 you would do the following:
Press the Esc key to go to normal mode.
Type :3,5d and hit Enter to delete the lines.
You can also use the following characters to specify the range:
. (dot) - The current line.
$ - The last line.
% - All lines.
Here are a few examples:
:.,$d - From the current line to the end of the file.
:.,1d - From the current line to the beginning of the file.
:10,$d - From the 10th line to the end of the file.
Delete All Lines
To delete all line you can use either the % symbol that represents all lines or the 1,$ range:
Press the Esc key to go to normal mode.
Type :%d and hit Enter to delete all the lines.
Deleting Lines Containing a Pattern
The syntax for deleting multiple lines based on a specific pattern is as follows:
:g/<pattern>/d
The global command (g) tells the delete command (d) to delete all lines containing the <pattern>.
To match the lines not matching the pattern, add an exclamation mark (!) before the pattern:
:g!/<pattern>/d
The pattern can be a literal match or regular expression . Below are some examples:
:g/foo/d - Delete all lines containing the string “foo”. It also removes line where “foo” is embedded in larger words, such as “football”.
:g!/foo/d - Delete all lines not containing the string “foo”.
:g/^#/d - Remove all comments from a Bash script. The pattern ^# means each line beginning with #.
:g/^$/d - Remove all blank lines. The pattern ^$ matches all empty lines.
:g/^\s*$/d - Remove all blank lines. Unlike the previous command, this also removes the blank lines that have zero or more whitespace characters (\s*).