Settings

Enable SSHD logging

nano /etc/ssh/sshd_config

# Logging
SyslogFacility AUTH
LogLevel INFO

##################
# SysLogFacility #
#- DAEMON        #
#- USER          #
#- AUTH          #
#- LOCAL0        #
#- LOCAL1        #
#- LOCAL2        #
#- LOCAL3        #
#- LOCAL4        #
#- LOCAL5        #
#- LOCAL6        #
#- LOCAL7        #
##################
# Ref:
# → https://docs.ssh.com/manuals/server-zos-admin/54/Configuring_Logging_in_sshd2.html
# → https://docs.ssh.com/manuals/server-zos-admin/65/Server-auditing-SysLogFacility.html

Screenshot-2023-07-19-at-5 48 42-PM

Linux File Permissions

linux-introduction-file-permissions-4-2054323870

image

Enable Advanced Security Audit Policy

gedit

IOPS test command for linux

dnf install -y fio
fio --name=benchmark --size=1G --runtime=30 --filename=tempfile --ioengine=libaio --rw=randread --iodepth=32

Useful commands

# System info
nmtui
lscpu
uname - a
free -m
hostnamectl
timedatectl

# Storage
du -csh
lsblk
df -h /
fdisk -l
fdisk /dev/sda
vgdisplay

# Network
route -n
ip a

# Process
pgrep
pkill
ps -elf

# Permissions
visudo
chmod
chown

/sbin/sysctl -p  # Command load kernel settings from /etc/sysctl.conf. 

Storage Options

Extending a logical volume in a virtual machine running Red Hat or Cent OS

Option 1: Resize Without Adding a New Disk

growpart /dev/sda 3
lvextend -r -l +100%FREE /dev/mapper/centos-opt
partprobe

OR

fdisk /dev/sda
1. "d" to delete the only partition /dev/sda has.
2. "n" to create a new one. Running "n" will make fdisk interactively ask you some parameters for partition creation, you can just hit enter so it uses the default values.
3. Running the previous command does not write the changes to disk, to do this, you need to run the "w" command.
partprobe
lsblk
xfs_growfs /dev/sda1

Option 2: Resize by Adding a New Disk

# Create physical volume on the new disk
pvcreate /dev/sda

# Display volume group information
vgdisplay

# Extend volume group with the new disk
vgextend <VG Name> /dev/sda

# Resize logical volume
lvextend -r -l +100%FREE /dev/mapper/<VG Name>-opt

# Update partition information
partprobe