README.md

Linux

References

Network

Problem: List all programs listening for a network connection

$ netstat -tunlp

Argument disambiguation:

-t or --tcp displays TCP network connections

-u or --udp displays UDP network connections

-n or --numeric Shows numeric IP addresses instead of attempting to discover host

-l or --listening Shows active listening sockets

-p or --program Shows the Process ID (PID) and Program name that the socket belongs to

Problem: Send packets from a specific network interface Example using ping

$ ping -I wg0 -C4 example.com
$ ping -I 10.0.0.1 -C4 example.com

Argument disambiguation:

-I takes an address or interface name. It works differently depending on if an address or interface is provided.

Drive Management

Checking a filesystem for bad blocks

Use mkfs

mkfs -c /dev/sda
mkfs -c /dev/sda1

Partitioning a new disk

Reading

You can discover more about drives attached to the computer with the following tools. Drives will always be under /dev/.

Drives attached via SCSI or SATA will be labeled /dev/sd* Drives attached via IDE ribbons will be labeled /dev/hd*

lsblk

parted -l

fdisk -l

When we partition a disk, we want to prefer parted because it can create a Globally Unique Identifiers Partition Table, which help administrators mount drives without needing to use MSDos partition maps in /etc/fstab. If we opt for the older fdisk, or cfdisk, we will be constrained to using MSDos partition maps.

According to techtitbits.com ,in 2018, there is some difficulty in using the parted command in noninteractive mode. Under certain conditions, like using a TTY-less SSH session, noninteractive mode may behave unpredictably, and will require the use of ---pretend-input-tty.

# Noninteractive parted

## Create 1 partition of largest size
parted -s /dev/sda mklabel msdos
parted -s /dev/sda mkpart primary ext4 0% 100%

## Format
mkfs.ext4 /dev/sda1

## Find the UUID of the new partition
lsblk -o UUID /dev/sda1

## Add the partition to fstab for auto-mount on boot
UUID=$(lsblk -o UUID /dev/sda1 | tail -n 1)
echo "UUID=$UUID       /mnt/data/somewhere     ext4    defaults,nofail" \
    | tee -a /etc/fstab

Deleting a partition

Reference $partition_number from either parted print all or the natural partition number /dev/sdN

parted rm $partition_number

Reloading filesystem table /etc/fstab

Reload fstab without re-mounting mountpoints that are already mounted

mount -av

Management

Logrotate

Reading:

Matthew Walther