There are a lot of articles on the Internet about improving OpenVPN speed, and often they are all focused on the settings of the server-client itself, packet sizes, encryption algorithms or disabling them. Everyone compares OpenVPN to a WireGuard. WireGuard works in kernel space and that’s what determines everything. Compared to userspace for openvpn. But that’s not quite true.

Here I must immediately clarify, that the given method of solving the problem is specific for virtual machines with small memory size, from 1Gb to 8Gb, in other cases you need to compare memory, link bandwidth and speed.

Here is a list of dynamically set values ​​relative to the system memory size:

• sysctl net.core.rmem_default
• sysctl net.core.rmem_max
• sysctl net.core.wmem_default
• sysctl net.core.wmem_max
• sysctl net.core.somaxconn
• sysctl net.core.netdev_max_backlog
• sysctl net.core.optmem_max
• sysctl net.ipv4.udp_mem
• sysctl net.ipv4.udp_rmem_min
• sysctl net.ipv4.udp_wmem_min
• sysctl net.ipv4.tcp_mem
• sysctl net.ipv4.tcp_rmem
• sysctl net.ipv4.tcp_wmem
• sysctl net.ipv4.tcp_synack_retries
• sysctl net.ipv4.tcp_keepalive_time
• sysctl net.ipv4.tcp_max_tw_buckets

Storing cryptsetup headers separately has some advantages, firstly, without them, the block device itself is a set of Entropy, from which it is impossible to determine the type of partition / encryption / device.
Secondly, it is a small file that can be easily backed up without using dd.

Simple cheat sheet

Generate a password.

cat /dev/urandom | tr -dc '[[:print:]]' | fold -w 256 | sed 's/ //g' | fold -w128 | head -n 1

Looking for whatever with low power consumption.
Found modules on mediatek, download documentation for SoM (System on Module).
You scroll through in search of how much the chip consumes.

Required packages apt install fontforge и pip install fonttools.

Let’s decide on the necessary glyphs: we need Latin, Cyrillic, special characters, including some Greek symbols (ΣΩαβγμ), Greek analogues that are similar in style but have different codes (∆∑µ), and a few more that can be used somewhere in the text or as elements to replace graphics (♪♫♬).

Why are there multiple variants of similar glyphs with different codes?

Because the µ (mu U+00b5) symbol and the Greek letter μ (mu U+03bc) in extended fonts can have their own glyph with different shapes, or, conversely, a common glyph, where similar characters in shape refer to the same glyph. Or, for example, the Greek Σ (Sigma U+03a3) is not the same as the symbol ∑ (summation U+2211).
But perhaps these symbols look the same on your screen.

Without further explanation

parted -a optimal /dev/sda
unit MiB
print free

#    Number  Start     End        Size       Type     File system     Flags
#            0,03MiB   1,00MiB    0,97MiB             Free Space
#     1      1,00MiB   1025MiB    1024MiB    primary  ext4            boot
#     2      1025MiB   5121MiB    4096MiB    primary  linux-swap(v1)
#     3      5121MiB   70657MiB   65536MiB   primary  ext4
#            70657MiB  476940MiB  406283MiB           Free Space