Category sysadmin

Ubuntu 18.04 Terminal Boot

Here are a series of commands to get Ubuntu 18.04 to boot into terminal mode, with various extras on how to get an automatic menu on boot up.

Skipping Graphical Boot

If you want to skip the graphical login screen, hit [Shift] or [Esc] before you see the grub menu to get to the grub menu. Add these features to the linux command:
systemd.unit=multi-user.target
Then hit Ctrl-X.

Changing the Default Boot Target

Become root. In /lib/systemd/system, change the default.target symlink:

# rm default.target; ln -s multi-user.target default.target
# systemctl daemon-reload

Checking the Filesystem Every Boot

If you do the first command above with a semicolon, you can still use tab-completion. Next, we go to /etc/default and update the grub settings:

# cd /etc/default
# vim grub
Change GRUB_CMDLINE_LINUX_DEFAULT to this value:
"fsck.mode=force fsck.repair=yes"

Run update-grub2:
# update-grub2

Reinforce this behavior by using tune2fs to make each file system run a check each boot. What file systems are you running?

# lsblk -o NAME,MOUNTPOINT # will produce output kinda like:
sda   
  sda1  /boot
  sda2  /
  sda3 [SWAP]
  sda4 /home

Running these command will make sda1, sda2, sda4 all check every mount:

# tune2fs -c1 /dev/sda1
# tune2fs -c1 /dev/sda2
# tune2fs -c1 /dev/sda4

Reboot:
# reboot

That shouldn’t take too long. You have a tty login now.

Creating an Automatic Menu

I’m disabling a few things:

systemctl disable snapd.service wpa_supplicant.service unattended-upgrades.service cups-browserd.service cups.service
systemctl daemon-reload

There will be lots of snaps you don’t want:

snap list --all | awk '/gnome|gtk/{print $1, $2}' | while read snapname snaprevision; do snap remove "$snapname" --revision="$snaprevision"; done
This didn't work well, maybe snap remove "$snapname" is enough
You are logged in on tty1 by default. (I don't know why tty0 exists.) Following this guide, create this directory:
# cd /etc/systemd/system
# mkdir getty@tty1.service.d
# cd getty@tty1.service.d
# vim override.conf
[Service]
ExecStart=
ExecStart=-/root/onboot.bash
StandardInput=tty
StandardOutput=tty
# vim /root/onboot.bash

#!/bin/bash
echo "This is a sound recorder appliance. Hit a key to start recording."
RECORDING=0
while true; do
  read -sn1 KEY
  if [[ $RECORDING = 0 ]]; then
    RECORDING=1
    echo "Now recording"
    /root/start-recording.bash
  else
    RECORDING=0
    echo "Recording stopped"
    /root/stop-recording.bash
  fi
done

 

# chmod +x /root/onboot.bash
# systemd daemon-reload
# reboot

All you have to do then is record things with the start-recording.bash and stop-recording.bash scripts.

Advertisements

ZFS Snapshot alias

Add this to your .bash_aliases for fun and profit:

function Snapshot () {
  local dst=""
  local atnam=""
  if [ -z "$1" ]; then
    dst=`df -l . | tail -1 |awk '{print $1}'`
  else
    if [[ $1 = *@* ]]; then
      atnam="${1##*@}"
      dst="${1%%@*}"
    fi
    dst=`df -l "$dst" | tail -1 |awk '{print $1}'`
  fi
  [ -z "$dst" ] && echo "wants file system name to snapshot" && return 1
  local NOW=`date +%Y%m%d-%H%M%S`
  [[ $dst = /* ]] && dst="${dst#/}"
  [[ $dst = */ ]] && dst="${dst%/}"
  [[ x$atnam = x ]] && atnam=$NOW
  sudo zfs snapshot "${dst}@${atnam}"
}

 

Ubuntu 18.04 Netplan!

This was unexpected, but I think I’m coping well. These are my notes on configuring netplan networking on my Ubuntu 18.04 server.

  1. systemctl disable NetworkManager.service NetworkManager-wait-online.service
  2. systemctl mask NetworkManager-wait-online.service
  3. systemctl daemon-reload
  4. apt install bridge-utils -y
  5. edit /etc/udev/rules.d/70-net.rules 
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="c8:70:00:9f:d7:72", NAME="eth0"
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:60", NAME="eth1"
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:61", NAME="eth2"
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:62", NAME="eth3"
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:63", NAME="eth4"
  6. edit /etc/netplan/01-netcfg.yaml 
      version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: no
      dhcp6: no
    eth1:
      dhcp4: no
      dhcp6: no
    eth2:
      dhcp4: no
      dhcp6: no
    eth3:
      dhcp4: no
      dhcp6: no
    eth4:
      dhcp4: no
      dhcp6: no
  bridges:
    br0:
      dhcp4: yes
      dhcp6: no
      interfaces:
         - eth0
      routes:
         -  to: 192.168.100.0/24
            via: 192.168.45.3
            on-link: true
    br1:
      dhcp4: no
      dhcp6: no
      addresses: [10.45.0.1/24]
      interfaces:
         - eth1
    br2:
      dhcp4: no
      dhcp6: no
      addresses: [10.45.1.1/24]
      interfaces:
         - eth2
    br3:
      dhcp4: no
      dhcp6: no
      addresses: [10.45.2.1/24]
      interfaces:
         - eth3
    br4:
      dhcp4: no
      dhcp6: no
      addresses: [10.45.3.1/24]
      interfaces:
         - eth4
  7. sudo netplan generate
  8. sudo netplan apply
  9. reboot

Without my eth1-eth4 devices plugged into a switch, rebooting takes forever.

ZFS Rebuild Script

I’ve rebuilt my zfs modules often enough that I’ve written a script to do a clean build that should avoid old kernel modules and old libraries.

#!/bin/bash
sudo find /lib/modules -depth -type d -iname "spl" -exec rm -rf {} \;
sudo find /lib/modules -depth -type d -iname "zfs" -exec rm -rf {} \;
sudo find /usr/local/src/ -type d -a \( \
   -iname "spl-*" \
   -o -iname "zfs-*" \
   \) -exec rm -rf {} \;

sudo find /usr/local/lib/ -type f -a \( \
   -iname "libzfs*" \
   -o -iname "libzpool*" \
   -o -iname "libnvpair*" \
   \) -exec rm -f {} \;

cd spl
git reset --hard HEAD
git checkout master
git pull
git tag | tail -1 | xargs git checkout
./autogen.sh && ./configure && make -j13 && sudo make install
cd ../zfs
git reset --hard HEAD
git checkout master
git pull
git tag | tail -1 | xargs git checkout
./autogen.sh && ./configure && make -j13 && sudo make install

sudo update-initramfs -u
sudo update-grub2

Pulling 200 Feet of Cable

We wrapped five 200 foot segments of the direct burial line back onto the original spool so we could tape them all together. The paint cans are ballast to keep the spool from sliding around.

Our first pull attempt was thwarted by friction. We yanked it back and greased the nose of the cable and it went through well.

The cables then had to be completely un-spooled again, the opposite end taped, and then pushed through three more short conduit runs. It comes out of the wall in the sound room of the sanctuary.

Made it Fit

This is a Digium card, clearly intended for a 1U or ATX case. One of my goals is to reduce the number of high speed fans in the lab, so I repurposed my Lanner chassis. Using a typical twist drill bit is a poor choice for the job of an end mill, but it came out ok when I put a rotary steel brush to the aluminum plate.

20180216_152343-asterisk1

Soldered new cabling

20180216_152355-asterisk2

Heat shrinked cable ends fit nicely

Thoughts on Media Hosting

If the recordings are licensed in the public domain, out of copyright, or creative commons, archive.org provides free audio hosting. http://archive.org/about/faqs.php#224

All of the services listed are not a substitute for an offline cold backup, just a reminder. Site content on Amazon or YouTube can disappear because of copyright dispute claims or policy conflicts like Terms of Service violation or other arbitrary policy changes.

Commercial podcast hosting appears to be tiered by upload amount per month; this is a comparison: https://www.thepodcasthost.com/websites-hosting/best-podcast-hosting/

The advantages of some podcast hosting services is that they might have automatically generated RSS feed services, and might provide integration with other podcast syndicators such as rdio.com or stitcher.com. No particular service is better than others at iTunes integration because iirc, iTunes plays by its own rules.

Moving podcast hosting often involves altering podcast feeds which can alter the subscribers content (like flood it with hundreds of ‘unread/new’ items), or make it appear to have stopped updating altogether. It definitely takes some homework to prepare for a move.

Hosting videos can also be done on vimeo.com or anything that hosts files. Video hosting services typically differentiate themselves by their online players (mobile friendly vs High Definition).

Live streaming services are available from both YouTube, vimeo.com, or other services like ScaleEngine.com or Twich. Converting a live stream to a hosted video takes forethought to record the video, sometimes on a separate device.