Setting up Proxy over SSH on Linux

Initiate a ssh connection to the server or device you want to use as a proxy. You can change the port to something else if so desired.

ssh username@ipaddress -D 1880

Log in and leave the session running

You can now setup your computer or browser to use the Proxy.
Specify SOCKS Host, hostname is either localhost or 127.0.0.1, the port is 1880.

Firefox example below.

Secure Erase Hard Drive using DD

The following commands are dangerous! Proceed with caution!

Change /dev/sdX to your drive. Make sure you get the correct drive, or you could wipe you main system.

dd if=/dev/zero of=/dev/sdX bs=1M status=progress

The status=progress part shows how much dd has writen. Helpful to gauge how far along it is.

If you want a more secure way to erase the drive, change zero to random. Makes it slower, but should be more secure.

dd if=/dev/random of=/dev/sdX bs=1M status=progres

Side note, these commands should work in macOS, but you may need to drop the status=progress option.

semanage Allow and Delete ports in CentOS

The commands are for CentOS, but should work on Fedora and RedHat.

If semanage is not installed refer to here.

You would typically use this along with the systems firewall to allow a port through.  Guide for firewalld and iptables.  If you change it in the firewall and fail to add/edit it in semanage you can potentially get weird behavior like sshd not wanting to start after changing the port.

Add port

semanage port -a -t ssh_port_t -p tcp 2222

The above command allows the sshd service to start, using port 2222.

List allowed ports

semanage port -l

You can use grep to filter the results

Example:

[admin@localhost ~]# semanage port -l | grep ssh
ssh_port_t tcp 2222, 22
[admin@localhost ~]#

Delete port

semanage port -d -p tcp 2222

Other examples

Allow SNMP

semanage port -a -t snmp_port_t -p udp 161

 

Parted resizing notes

Launch parted with the following command.  Specify the disk you want to modify.  In this case /dev/sda.

sudo parted /dev/sda

Print partition and available free space.  If you just run print, it will not show you the available free space.

(parted) print free

You can resize, or rather extend a partition using the “resizepart” command inside parted.  Command syntax is as follows

(parted) resizepart PartitionNumber End

Example: Resize partition 1 to 30GB.  Note you’ll need to specify the end part with the GB, otherwise, you’ll be shrinking the partition or making a mess…  You can see what space is available with the “print free” command above

(parted) resizepart 1 30GB

After you have run the resizepart in parted, you’ll need to grow the filesystem, so run one of the following commands from the local shell.

resize2fs /dev/sda1

Or for XFS partitions

xfs_growfs /dev/sda1

You can check the partition size with

df -h

or

sudo fdisk -l /dev/sda