RedHat RHCSA common workflows

_Helper files

többiektől:
https://onedrive.live.com/?authkey=%21ABRgmNAPtpE8n7E&cid=B70386FBC114FFC7&id=B70386FBC114FFC7%215152&parId=root&o=OneUp

partitioning & common database issues:
https://imgur.com/a/hsIw1hx

RHLEARN:
rhlearn.gilmore.ca

_Network Configuration

## Configure the network

1. nmtui

2. nmcli

A) If you don't have any NetworkManager connection:

A.1) Add new NetworkManager connection:

nmcli con add con-name "Exam" ifname eth0 type ethernet ip4 172.25.201.X/24 gw4 172.25.201.254
nmcli con mod "Exam" ipv4.dns "172.25.201.254"
nmcli con mod "Exam" ipv4.method manual
nmcli con mod "Exam" connection.autoconnect yes

A.2) Activate new NetworkManager connection:

nmcli con up "Exam"

A.3) Verify NetorkManager connection and /etc/resolv.conf file:

nmcli con show "Exam"

cat /etc/resolv.conf

-------------------------------------------------------------------------

B) If you already have NetworkManager connection:

B.1) Add another NetworkManager connection:

nmcli con add con-name "Exam" ifname eth0 type ethernet ip4 172.25.201.X/24 gw4 172.25.201.254
nmcli con mod "Exam" ipv4.dns "172.25.201.254"
nmcli con mod "Exam" ipv4.method manual
nmcli con mod "Exam" connection.autoconnect yes

B.1.2) Activate new NetworkManager connection:

nmcli con up "Exam"

B.1.3) Disable old NetworkManager connection to Automatically connect during system start-up:

nmcli con mod "System eth0" connection.autoconnect no

B.1.4) Check NetworkManager connections and verify new NetworkManager connection:

nmcli con show
nmcli con show --active
nmcli con show "Exam"

B.1.5) optional - remove old unwanted NetworkManager connection:

nmcli con del "System eth0"

B.2) Edit already existing NetworkManager connection:

nmcli con mod "System eth0" ip4 172.25.201.X/24
nmcli con mod "System eth0" ipv4.gateway 172.25.201.254
nmcli con mod "System eth0" ipv4.dns "172.25.201.254"
nmcli con mod "System eth0" ipv4.method manual
nmcli con mod "System eth0" connection.autoconnect yes

B.2.1) Activate updated NetworkManager connection:

nmcli con up "System eth0"

B.2.2) Verify updated NetworkManager connection:

nmcli con show "System eth0"

-------------------------------------------------------------------------

## Useful nmcli commands

# To see a list of network devices and their state:

nmcli dev
or
nmcli dev status

# Show detailed information about devices:

nmcli dev show
and
nmcli dev show (device)

# To bring down an interface and temporarily disable autoconnect use command:

nmcli dev dis (device)

# Connect the device

nmcli dev con (device)

# To disable or enable all managed interfaces use command:

nmcli net off
nmcli net on

# To turn off wifi:

nmcli r wifi off

-------------------------------------------------------------------------

### Source -> https://www.youtube.com/watch?v=v-soSvSsw18&feature=share


┌───────────────────────────┤ Edit Connection ├───────────────────────────┐
│                                                                         │
│         Profile name Exam____________________________________           │
│               Device ________________________________________           │
│                                                                         │
│ ═ ETHERNET                                                    <Show>    │
│                                                                         │
│ ╤ IPv4 CONFIGURATION <Manual>                                 <Hide>    │
│ │          Addresses 10.0.2.103/8_____________ <Remove>                 │
│ │                    <Add...>                                           │
│ │            Gateway 10.0.2.1_________________                          │
│ │        DNS servers 10.0.2.1_________________ <Remove>                 │
│ │                    <Add...>                                           │
│ │     Search domains <Add...>                                           │
│ │                                                                       │
│ │            Routing (No custom routes) <Edit...>                       │
│ │ [ ] Never use this network for default route                          │
│ │ [ ] Ignore automatically obtained routes                              │
│ │ [ ] Ignore automatically obtained DNS parameters                      │
│ │                                                                       │
│ │ [ ] Require IPv4 addressing for this connection                       │
│ └                                                                       │
│                                                                         │
│ ═ IPv6 CONFIGURATION <Automatic>                              <Show>    │
│                                                                         │
│ [X] Automatically connect                                               │
│ [X] Available to all users                                              │
│                                                                         │
│                                                           <Cancel> <OK> │

Access

# Change to root user:

sudo su - 

-------------------------------------------------------------------------
# Change to some user:

sudo su - username

sudo -i -u username

-------------------------------------------------------------------------

# Change the owner

chown newuser file-name

chown -R newuser dir-name

-------------------------------------------------------------------------

# Change the group

chgrp newgroup file-name

chgrp -R newgroup dir-name

-------------------------------------------------------------------------

# Change the password of any user

passwd username

-------------------------------------------------------------------------
# Get and Set the access control list (ACL) of a FILE

getfacl file-name

setfacl -m "u:username:rwx" file-name

-------------------------------------------------------------------------
# Get and Set the access control list (ACL) of a DIRECTORY

getfacl /path/to/the/folder

setfacl -Rm "u:username:rwX" /path/to/the/folder  (g for group)

setfacl -Rm "d:u:username:rwx" /path/to/the/directory (default access to the file)

Apache

Apache accesses several directories on the file system:
– The apache binary, apache modules and shared libraries in /usr/bin, /usr/lib 
– Confguration fles in /etc/httpd/* 
– Web content in /var/www/html (by default) 
– Server logs in /var/log/httpd/* 
– Executable scripts (cgi-bin, python, php, …) in the web application directories for e.g. /usr/share/owncloud/*
– Documentation in /usr/share/doc/apache (The documentation is available in html format served as a web site) 
– Possible more custom fles/directories
-------------------------------------------------------------------------

sudo yum -y install httpd httpd-manual
-------------------------------------------------------------------------
systemctl enable httpd.service
-------------------------------------------------------------------------
systemctl status httpd
-------------------------------------------------------------------------
systemctl start httpd.service
or 
apachectl start
-------------------------------------------------------------------------
# Network security

firewall-cmd --permanent --add-service=http --add-service=https
firewall-cmd --reload

-------------------------------------------------------------------------
# To serve the default content outside, a new context rule must be addded

semanage fcontext -a -t httpd_sys_content_t '/new/location(/.*)?'

-------------------------------------------------------------------------
# Allow writable access for a group to the DocumnetRoot

setfacl -R -m g:groupname:rwX /var/www/html

setfacl -R -m d:g:groupname:rwx /var/www/html
-------------------------------------------------------------------------
# Change ServerAdmin

/etc/httpd/conf/httpd.conf

content of file: ServerAdmin username (webmaster@serverX.example.com)

# Create default content page

in /var/www/html/ we create index.html

write someting to the file using vim
-------------------------------------------------------------------------
-------------------------------------------------------------------------

Source -> https://rhlearn.gilmore.ca/node/156/take (redhat)

Source -> https://www.youtube.com/watch?v=PatSrUO4o8w (video tutorial)

Source -> https://www.youtube.com/watch?v=HlF1egrT4Wg (video tutorial 2)

Copy MariaDB datastore to new partition

# Create partition with the type 8e (Linux LVM)

fdisk /dev/hdb

(new)     n
(primary) p
(type)    t
(list)    L   (or just simply enter 8e directly)

press p to display the partition setup
press w to write the partition table

-------------------------------------------------------------------------

# Create Physical Volume

pvcreate /dev/vdb1

-------------------------------------------------------------------------
# Create Volume Group

vgcreate vg_name /dev/vdb1 (can vary)

-------------------------------------------------------------------------
# Create Logical Volume

lvcreate -n lv_name -L 5G vg_name (can vary -l 100%FREE) 

Source -> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/5/html/logical_volume_manager_administration/lv

-------------------------------------------------------------------------
# Create File System

mkfs -t xfs -L "label" /dev/vg_name/lv_name

or

mkfs.xfs -L "label" /dev/vg_name/lv_name

-------------------------------------------------------------------------
# Create temporary dir

mkdir /mnt/mysql (/mnt exists)

-------------------------------------------------------------------------
# Do mounting

mount /dev/vg_name/lv_name/ /mnt/mysql

-------------------------------------------------------------------------
# Stop the Mariadb service

systemctl stop mariadb

-------------------------------------------------------------------------
# Source of the copy operation

cat etc/my.cnf | grep datadir

-------------------------------------------------------------------------
# Copy the datastore directory to the new location

cp -a /var/lib/mysql /mnt/

cp -a /var/lib/mysql/* /mnt/mysql

-------------------------------------------------------------------------
# Check the permissions

ls -laZ /mnt

-------------------------------------------------------------------------
# Unmount new file system from the temporary directory

umount /mnt/mysql

-------------------------------------------------------------------------
# Start Mariabd

systemctl start mariadb

-------------------------------------------------------------------------
# Stop the Mariadb service

systemctl stop mariadb

-------------------------------------------------------------------------
# Make new dir

mkdir /backup

-------------------------------------------------------------------------
# Move all the files into new dir

mv var/lib/mysql/* /backup/

-------------------------------------------------------------------------
# Mount Persistently

1) vi /etc/fstab

2) file content:  /dev/vg_first/lv_fisrt                     /var/lib/mysql   auto      defaults            0  0

3) mount -a

-------------------------------------------------------------------------
# Start Mariabd

systemctl start mariadb

-------------------------------------------------------------------------
# Check Mariabd status

systemctl status mariadb

Earlier tasks

__ MYSQL DUMP __
mkdir /backup
mysqldump --all-databases > /backup/full-dump.sql


__ APPEND TO PATH __
vi ~/.bash_profile
# add the following line to the end:
export PATH="/root/development/bin:$PATH"


__ CREATE SWAP FILE __

dd if=/dev/zero of=/swap.file bs=1M count=17

chmod 600 /swap.file
chown root:root /swap.file

mkswap /swap.file
# test it: swapon, swapoff

vi /etc/fstab     # and add the following to the end:
/swap.file    none    swap    sw    0  0



__ complicated wc+grep __
mkdir /mnt/iso
mount /exam-common/VBoxGuestAdditions.iso /mnt/iso
cd /mnt/iso
grep -rl "Solaris" | grep ".sh" | xargs wc -l   | head -n2


__ apache debug __
systemctl status apache -l
# invalid something:
yum provides <invalid-file-name>
yum reinstall <invalid-pkg-name>

#check content type (alternative path: /var/www/html)
ls -laZ /www-root/html
chmod apache:apache /www-root/html
semanage fcontext -a -t httpd_sys_content_type '/www-root/html(/.*)?'
# systemctl enable httpd      !!!!

File Systems

# Create File Systems

mkfs -t btrfs /dev/vdb1 (file systems: xfs, ext4..)

-------------------------------------------------------------------------

# Label (btrfs) File Systems 

btrfs filesystem label /dev/vdb1 "label-name"

-------------------------------------------------------------------------

# Label (ext4) File Systems 

e2label /dev/vdb1 label-name

-------------------------------------------------------------------------

# Label (xfs) File Systems 

xfs_admin -L "label-name" /dev/vdb1

-------------------------------------------------------------------------

# Mount File Systems

1. create new temprorary directory

mkdir tempdir
-------------------------------------------------------------------------
2. apply mount command

mount /dev/vdb1 /tempdir

df -h (check mounting)
-------------------------------------------------------------------------
3. cp -pr /home/* /tempdir/  
-------------------------------------------------------------------------
4.  umount /tempdir
-------------------------------------------------------------------------
5. Get partition's UUID

blkid /dev/vdb1

or

lsblk -o name,uuid
-------------------------------------------------------------------------
6. persistent mounting 

vi /etc/fstab

UUID=48516887-51fc-4930-af9f-735c9c0c3f2e  /home       btrfs    defaults        0  0

mount -a
-------------------------------------------------------------------------
7. view mounted FSs

mount | grep vdb1

-------------------------------------------------------------------------

Source -> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/s2-disk-storage-parted-create-part#s3-disk-storage-parted-create-part-mkfs

Mariadb

# Login to mysql

mysql -u root -p

-------------------------------------------------------------------------
# Create database

CREATE DATABASE databasename;

-------------------------------------------------------------------------
# Use database

use databasename;

-------------------------------------------------------------------------
# Create tables of the database

MariaDB [databasename]> CREATE TABLE example (
did TINYINT UNSIGNED NOT NULL AUTO_INCREMENT,
dname VARCHAR(20),PRIMARY KEY(did));

MariaDB [databasename]> CREATE TABLE example (
id TINYINT UNSIGNED NOT NULL AUTO_INCREMENT,
name VARCHAR(20),PRIMARY KEY(id));

-------------------------------------------------------------------------
# Show tables of the database

show tables;

-------------------------------------------------------------------------
# Show the schema or layout of the table using the DESCRIBE command

DESCRIBE databasename;

-------------------------------------------------------------------------

Source -> https://www.youtube.com/watch?v=qxPnGlIxYC8 (video tutorial)

Source -> https://www.theurbanpenguin.com/rhce-creating-a-database-in-mariadb-using-rhel-7-1/ (sql commands) 

Source -> https://mariadb.com/kb/en/library/what-to-do-if-mariadb-doesnt-start/ (What to Do if MariaDB Doesn't Start)

Other useful commands

netstat -tulnp
yum install mariadb mariadb-client
hostnamectl set-hostname <hostname>
setenforce Enforcing
blkid

vgextend <vg_name> /dev/sdc4

for i in /dev/sd[a-z];do parted $i unit s print; done

## blokk számolás:
stat <filename>
du -b <filename>

Partitions

## Create Partitions

# List disks:

a) lsblk
b) lsblk -o name,label,fstype

-------------------------------------------------------------------------

# Create MBR disk partition

fdisk /dev/vdb

n (new partition)

p (primary partition)

1 (default partition number) can vary

enter (fist sector) can vary

enter (last sector) can vary

enter or t (define the type)

w (write changes)

-------------------------------------------------------------------------

# Create GPT disk partition

gdisk /dev/vdb

n (new partition)

p (primary partition)

1 (default partition number) can vary

enter (fist sector) can vary

enter (last sector) can vary

enter or L (define the type)

w (write changes)

y

-------------------------------------------------------------------------

### Source -> https://rhlearn.gilmore.ca/node/357/take

SSH

# SSH into CLIENT computer:

  ssh username@desktopX

-------------------------------------------------------------------------

# Now that we are in the CLIENT computer, we do these commands:

  # first we try to log into the SERVER with our password, it should work
    ssh username@serverX
    exit

  # now we generate the key, and copy it onto the server
    ssh-keygen
    ssh-copy-id username@serverX
    
  # then we try to log into the SERVER again, this time it shouldn't ask for password
    ssh username@serverX

Users & Groups

## Add new user
useradd -m username (-m for the home directory) 

-------------------------------------------------------------------------

## Add new group
groupadd groupname

-------------------------------------------------------------------------

## Add user to the group
usermod -ag groupname username

-------------------------------------------------------------------------

Source -> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/s1-users-tools