Linux & Server on myl3z.me

Bootable USB from the Terminal

Mon, 01 Jan 0001 00:00:00 +0000

Bootable USB from the Terminal#

A bootable USB stick from an ISO — no extra tooling, just lsblk, umount and dd. The example writes a Debian netinst installer, but the steps are the same for any hybrid ISO. For what each command actually does, see lsblk, umount, dd, sync.

dd does not ask and has no undo. The wrong device name overwrites your system disk. Check the target twice before running it.

lsblk, umount, dd, sync

Mon, 01 Jan 0001 00:00:00 +0000

lsblk, umount, dd, sync#

The four commands you reach for when working with block devices on Linux: find one, release it, write to it, and make sure the data actually landed. They are put to use in Bootable USB from the Terminal.

lsblk — list block devices#

lsblk reads the device tree from the kernel (/sys/block) and prints it as a tree: physical drives as roots, their partitions as children. It needs no root privileges and touches nothing.

Static IP with ifupdown

Mon, 01 Jan 0001 00:00:00 +0000

Static IP with ifupdown#

A server other devices are supposed to reach needs an address that does not change. DHCP hands it whatever is free — possibly a different one after the router reboots, and every configuration pointing at the old one breaks. For a DNS server in particular that is not an option: its address is what every client has hardcoded.

A Debian install without a desktop manages networking through ifupdown and /etc/network/interfaces. NetworkManager and systemd-networkd solve the same problem but are not in play on a netinst system.

SSH Config and Key Login

Mon, 01 Jan 0001 00:00:00 +0000

Without configuration every connection is the same typing exercise:

ssh -i ~/.ssh/id_rsa xander@10.10.10.3

Address, user and key do not belong on the command line but in the client configuration at ~/.ssh/config. It states per host what the connection should look like — after that the alias is enough:

ssh dns01

The entry#

Host dns01
 HostName 10.10.10.3
 IdentityFile /home/xander/.ssh/id_rsa
 IdentitiesOnly yes

Line	Meaning
`Host dns01`	the name you type on the command line. Freely chosen and independent of the real hostname; everything up to the next `Host` belongs to this block
`HostName 10.10.10.3`	where the connection actually goes — IP or DNS name
`IdentityFile`	the private key for this connection. Its public counterpart (`.pub`) lives on the server
`IdentitiesOnly yes`	offer this key and nothing else

The block is a set of defaults, not a connection in itself. It applies to anything matching the alias — including scp, rsync and git, which all use the same SSH client:

Adding sudo

Mon, 01 Jan 0001 00:00:00 +0000

Adding sudo#

A fresh Debian install may have no sudo at all — and which way it goes depends on a choice made during installation whose consequence is never spelled out:

Root password in the installer	Result
set	root is enabled, `sudo` is not installed
left empty	root is locked, `sudo` is installed and the first user is added to the `sudo` group

So if you set a root password, you are met with sudo: command not found afterwards and have to add it yourself.

Base Packages After the Install

Mon, 01 Jan 0001 00:00:00 +0000

Base Packages After the Install#

A netinst installation without a desktop deliberately ships very little. That is the right starting point for a server — it keeps the attack surface and the update workload small — but it means tools only become noticeable when you need them. This page collects what was added to the homelab machine after the fact.

Whether something is missing at all is answered by:

command -v curl # path if present, otherwise empty and exit code 1
dpkg -l curl # package status: ii = installed and configured

curl#

sudo apt install curl

curl fetches data over HTTP, HTTPS and a dozen other protocols and writes it to stdout by default. On a server without a browser it is the standard tool for anything arriving over the network: install scripts, API calls, the quick check whether a service answers at all.

Pi-hole as a DNS Server

Mon, 01 Jan 0001 00:00:00 +0000

Pi-hole as a DNS Server#

Pi-hole is a DNS server with a filter. When a device asks for a domain that sits on a blocklist, Pi-hole does not pass the query on to the upstream but answers it itself — with an address that leads nowhere. The advantage over a blocker in the browser is where the filtering happens: name resolution is used by every device on the network, including the TV and a visitor’s phone, neither of which lets you install anything.

Choosing an Upstream DNS

Mon, 01 Jan 0001 00:00:00 +0000

Choosing an Upstream DNS#

Pi-hole does not know the addresses of the world. It knows blocklists and a cache — everything else it forwards to an upstream, and hands that answer back to the client. This makes the upstream the point at which the whole household’s name resolution leaves the local network.

The installer asks the question once, with Google as its first suggestion, and confirming it means making a decision without making one.

Linux & Server on myl3z.me

Bootable USB from the Terminal

Bootable USB from the Terminal#

lsblk, umount, dd, sync

lsblk, umount, dd, sync#

lsblk — list block devices#

Static IP with ifupdown

Static IP with ifupdown#

SSH Config and Key Login

SSH Config and Key Login#

The entry#

Adding sudo

Adding sudo#

Base Packages After the Install

Base Packages After the Install#

curl#

Pi-hole as a DNS Server

Pi-hole as a DNS Server#

Choosing an Upstream DNS

Choosing an Upstream DNS#