Avoid prompts when installing FreeBSD ports

The FreeBSD ports tree is wonderful for installing software but sometimes it can be a real pain. Recently I was trying to install Emby in FreeBSD because why not? The instructions were easy enough except for when I ran

make install clean

I was constantly barraged with choices for things. I want to assume the default on all of these and not be barraged with questions.

Thanks to stack exchange I learned it’s relatively easy to bypass all these questions. Simply add:


to the end of your make install clean statement to assume the defaults to all the questions for the package. The Emby guide is pretty comprehensive, but I would add this command at the bottom:

make install clean BATCH=yes


Measure SSH transfer speeds

SSH is a beautiful thing. In addition to remotely administering machines you can use it to transfer files. To do this one simply pipes the cat command on both ends. For example, to copy hello.txt on the source host to hi.txt on the destination host, the command would be:

ssh remote_host cat hello.txt | cat > hi.txt

The command takes the contents of hello.txt and pipes it over to the remote host. The cat command on the remote host takes what was piped to it as  input and the > sign instructs cat to take its input and output it to hi.txt.

A great way to measure transfer speeds using ssh between two hosts is to take /dev/zero on the source host and output it to /dev/null on the destination host. This bypasses any disk speed bottlenecks and only measures network throughput. Combine this with the pv command to get a nice graphical view of how fast the transfer is going.

ssh remote_host cat /dev/zero | pv | cat > /dev/null

The default options between my machines result in about a 65 megabytes a second transfer speed.


It turns out that the encryption cipher used makes a big difference on transfer speeds. Use the -c command to specify which cipher to use and see how much of a difference this makes. -o compression=no can also help with transfer speeds.

The fastest cipher I’ve found is arcfour. It’s touted as less secure, but for my local network I can accept the risk (thanks to slashdot for the discussion.)

ssh -c arcfour -o Compression=no remote_host cat /dev/zero | pv | cat > /dev/null


Using acrfour more than doubles the speed for me! Amazing.

Allow non-root users to mount disks

I came across a need today to allow a regular (non-root) user to mount disks in Ubuntu 14.04 Trusty Tahr. I usually use sudo but in this case I needed to be able to run photorec as a regular user.

The way to accomplish this is to add the regular user to the disk group. To accomplish this, run this command:

sudo usermod -a -G disk <username>

If you are logged in as that user, you will have to log out and log back in to receive the permissions. Once this is done you should be able to mount disks without using sudo or being root.

Disable IPv6 on an interface in Linux

After tethering my phone to my laptop and googling “what is my ip” I was surprised to find an IPv6 address. Apparently my mobile carrier has implemented IPv6. Bravo to them.

Unfortunately, when I initiated my VPN, which is supposed to tunnel all traffic through it, my IP address didn’t change. This is because my VPN is IPv4 only. My system prioritizes IPv6 traffic, so if I happen to go to any IPv6 enabled site such as google, my VPN tunnel is bypassed entirely.

I don’t like the security implications of this. The long term solution is to implement IPv6 with my VPN; however while traveling I won’t be able to do that. The short term solution is to simply disable IPv6 for the interface that has it, in my case usb0 as that is what is tethered to my phone.

This simple command will do the trick:

sudo sh -c 'echo 1 > /proc/sys/net/ipv6/conf/usb0/disable_ipv6'

Change USB0 to whatever interface you would like (or all of them) and you’re done! Thanks to this site for the information.