Dumbledore

Dumbledore is the Raspberry Pi 4 that we use as backup server. See also Voldemort.

Information

• CPU is a armv8, but as raspbian is 32-bit, it is reported as a 32-bit armv7l [1].

We need usual Debian ARM to get 64-bit apps running. But this may also not be as optimized as Raspbian.

lscpu
# Architecture:        armv7l
# Byte Order:          Little Endian
# CPU(s):              4

• Ethernet: IP 192.168.1.94, link/ether dc:a6:32:69:da:4e
• WiFi: IP DHCP, link/ether dc:a6:32:69:da:4f

Configuration

• Install Raspbian Buster 32-bit (2020-08-20-raspios-buster-armhf-full.zip) using imager_1.4_amd64.deb.
• Install NoMachine server (armv7 because 32-bit OS, also 64-bit is reported as not being optimized).

• Enable hardware acceleration in server settings.
• Add to /etc/NX/server/localhost/server.cfg [2]:

AvailableSessionTypes unix-remote,unix-console,unix-default,unix-application,shadow,unix-xsession-default,unix-gnome,unix-xdm,windows,physical-desktop

• Restart the server /etc/NX/nxserver --restart.

• Use static IP by editing /etc/dhcpcd.conf [3]:

+interface wlan0
+static ip_address=192.168.1.94/24
+#static ip6_address=fd51:42f8:caae:d92e::ff/64
+static routers=192.168.1.1
+static domain_name_servers=192.168.1.1 8.8.8.8 fd51:42f8:caae:d92e::1

• Enable ssh server. The simplest is to [4]:

# Either touch a file and reboot the device
sudo touch /boot/ssh
sudo reboot
# Or enable through systemd
sudo systemctl enable ssh
sudo systemctl start ssh

• Add to ~/.config/autostart/set_belgian_kbd.desktop:

[Desktop Entry]
Type=Application
Name=Set Belgian autostart
Comment=Set keyboard to Belgian layout
NoDisplay=true
Exec=sh -c '/usr/bin/setxkbmap be'

This should fix the wrong keyboard layout issue.

Borg server

We will use this pi4 as our main borg server.

• Add a user borg.
• Remove pi from sudo group.
• Disable no password sudo rule (/etc/sudoers.d/010_pi-nopasswd).
• Use strong password for user pi, borg and root.
• Install borg:

sudo apt install cython cython3
sudo apt-get install python3 python3-dev python3-pip python-virtualenv \
    libssl-dev openssl \
    libacl1-dev libacl1 \
    build-essential
sudo pip3 install borgbackup

• Add to /etc/ssh/sshd_config [5]:

  ClientAliveInterval 10
  ClientAliveCountMax 30

When using Wolverine NAS as storage

• Mount borg share as separate autofs host (/smb/borg/borg), restricted to borg user:

borg       -fstype=cifs,vers=1.0,_netdev,perm,iocharset=utf8,sec=ntlm,uid=borg,forceuid,gid=borg, \
    forcegid,file_mode=660,dir_mode=770,credentials=/etc/auto.master.d/smb.borg.borg.cred      ://wolverine/homes/borg

Now, using USB as storage

• Mount SSD in /etc/fstab:

UUID=0a6dab24-a62c-42d3-b032-315c33f1a2ca   /mnt/tera	ext4	defaults,noatime	0	1

• Link it to /home/borg/repo

sudo ln -sd /mnt/tera/borg /home/borg/repo

• Enable TRIM:

sudo systemctl enable fstrim.timer
sudo systemctl start fstrim.timer

• Example of authorized_keys:

command="/usr/local/bin/borg serve --restrict-to-path /home/borg/repo/",restrict ssh-ed25519 AAA... xyz@abc

Issues

• When booting headless, the session is not the same as the one we get when we boot with hdmi connected.

Samsung SSD 860 EVO through USB 3

• Can't get it to work with Advance USB 3 case (chipset ASMedia AS2105).
• Work currently on USB 2 enclosure.
• Refer: https://wiki.debian.org/SSDOptimization
• Refer: http://blog.neutrino.es/2013/howto-properly-activate-trim-for-your-ssd-on-linux-fstrim-lvm-and-dmcrypt/
• Must we enable TRIM?

• There are problem around NCQ (queued TRIM)...
• Samsung SSD 840 and Samsung SSD 850 are blacklisted in libata-core.c.
• However, there are patches telling that Queued TRIM is fully supported on Linux... or not [6], [7], [8], [9]

• Enabled TRIM with

sudo systemctl enable fstrim.timer
sudo systemctl start fstrim.timer