Tech Arkit: September 2018

nmtui Text Based User Interface RHEL 7 - RHCSA - Tech Arkit

nmtui - NetworkManager-tui Text User Interface for controlling NetworkManager

rpm -qa |grep NetworkManager-tui

nmtui edit connection_name

nmtui connect connection_name

nmtui-edit | nmtui edit {name | id}

nmtui-connect | nmtui connect {name | uuid | device | SSID}

nmtui-hostname | nmtui hostname

nmtui is a curses based TUI application for interacting with NetworkManager.When starting nmtui, the user is prompted to choose the activity to perform unless it was specified as the first argument.

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nmcli command-line tool for controlling NetworkManager - RHEL 7 - RHCSA

nmcli is a command-line tool for controlling NetworkManager and reporting network status. It can be utilized as a replacement for nm-applet or other graphical clients. nmcli is used to create, display, edit, delete, activate, and deactivate network connections, as well as control and display network device status.

Scripts: Utilize NetworkManager via nmcli instead of managing network connections manually. nmcli supports a terse output format which is better suited for script processing. Note that NetworkManager can also execute scripts, called "dispatcher scripts", in response to network events. See NetworkManager(8) for details about these dispatcher scripts.

Servers, headless machines, and terminals: nmcli can be used to control NetworkManager without a GUI, including creating, editing, starting and stopping network connections and viewing network status.

NetworkManager stores all network configuration as "connections", which are collections of data (Layer2 details, IP addressing, etc.) that describe how to create or connect to a network. A connection is "active" when a device uses that connection's configuration to create or connect to a network. There may be multiple connections that apply to a device, but only one of them can be active on that device at any given time. The additional connections can be used to allow quick switching between different networks and configurations.

Consider a machine which is usually connected to a DHCP-enabled network, but sometimes connected to a testing network which uses static IP addressing. Instead of manually reconfiguring eth0 each time the network is changed, the settings can be saved as two connections which both apply to eth0, one for DHCP (called default) and one with the static addressing details (called testing). When connected to the DHCP-enabled network the user would run nmcli con up default , and when connected to the static network the user would run nmcli con up testing.

nmcli monitor

nmcli connection {show | up | down | modify | add | edit | clone | delete | monitor | reload | load | import | export} [ARGUMENTS...]

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13 Regular Expression with Grep Command RHCSA - Tech Arkit

1. Check Grep version

grep -V

2. Search single word in single file / multifles

grep string *

3. Search Multiple words in single file / multiple files

grep -E 'word1|word2'

4. Seach text which is not maching to string

grep -v "String" fileName

5. Print the matching string and its before lines

grep ens33 -A 4

6. Print the matching string and its after lines and its around lines

grep enss33 -B 4

grep ens33 -C 4

7. Search a string Recursively

grep -r string fileName

8. Grep the string with highlighted in color

grep --color=auto string file Name

export GREP_COLOR='1;30;43'

9. display the lines which does not matches all the given strings

grep -v -e "a" -e "b" -e "c" filename.txt

10. Get the count of given string from file

grep -c string filename

11. Search for files which are matching to the given string

grep -l this demo*

12. Beginning of line ^ using cap symble

grep "^Nov 10" messages.1

13. End of the line $ using dollar symble

grep "terminating.$" messages

? The preceding item is optional and matched at most once.

* The preceding item will be matched zero or more times.

+ The preceding item will be matched one or more times.

n The preceding item is matched exactly n times.

n, The preceding item is matched n or more times.

,m The preceding item is matched at most m times.

n,m The preceding item is matched at least n times, but not more than m times.

From the above output you can come to know when all the messages has got interrupt. Just like ^ matches the beginning of the line only if it is the first character, $ matches the end of the line only if it is the last character in a regular expression.

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SELinux - Security Enhanced Linux Explained RHEL 7 - RHCSA - TechArkit

SeLinux : Security Enchanced Linux

SeLinux will support

. Port Level Security

. Sevice Level Security

. File Level Security

simply we can say 3 layer secuity.

SeLinux having 3 modes to manage security.

1. Enforcing: which means SeLinux is running with full enforcing mode, simple enabled mode.

2. Permissive: Permissive also says that SeLinux is running but it will not enforce, it will only logs the information.

3. Disabled: disable mode is simply disabled. SeLinux not in use.

Immediatly we get an question in mind that why there are three modes, Enable and disable modes are enough right.

Yes, i also got the same question when i was learning SeLinux. There is a reason behind that.

When we want to change the SeLinux mode from Enforcing to disabled we have to edit the configuration file /etc/selinux/config and change the SELINUX=disabled, config file will not be effected until unless server is rebooted.

Same for the changing the disabled mode to Enforcing mode.

but if you want to change Selinux mode from Enforcing to permissive doesn't required an reboot.

Now we understand that why SeLinux is disgned to have 3 modes.

Whenever you change the SeLinux mode from disable to enforcing after the reboot it will relabel all the SeLinux policies.

whenever you changed the SeLinux mode from Enforcing to Disabled after the reboot all the SeLinux policies will not go off, policies still exists but will not enforce.

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Tech Arkit

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Network Settings Using GUI RHEL 7 - RHCSA - Tech Arkit

nmtui Text Based User Interface RHEL 7 - RHCSA - Tech Arkit

nmcli command-line tool for controlling NetworkManager - RHEL 7 - RHCSA

New Network Concept Network Profiles RHEL 7

13 Regular Expression with Grep Command RHCSA - Tech Arkit

SELinux - Security Enhanced Linux Explained RHEL 7 - RHCSA - TechArkit