Org Wiki

Autostart desktop with given user account Source

> sudo vi /etc/lightdm/lightdm.conf

Under section [SeatDefaults], add:

autologin-user=wim

Extra for RasPi:

> sudo vi /usr/bin/raspi-config

In do_boot_behaviour(), change given line to:

if id -u wim > /dev/null 2>&1; then

Reboot.

Source

Look up these lines in lightdm configuration file, uncomment them and customize to your preference.

[Seat:*]
#autologin-user=
#autologin-user-timeout=0

Also did following (Source, may not be necessary):

To activate autologin when lightdm is the display manager, open (as root) /etc/lightdm/lightdm.conf, uncomment (delete "#") and change the appropriate lines in "session-wrapper" to:

autologin-user=roger,
autologin-user-timeout=0.

• Check what Debian version you are running on your Linux system

  Works on Debian and openSuse:

> lsb_release -a

and

> cat /etc/issue

Debian:

> cat /etc/debian_release

Check 64-bit:

> uname -m
aarch64       # ARM 64-bit

> nm -D <so-name> | grep ' T '

Exported symbols have 'T', non-exported symbols have 't'

> ldd <prog_name>

> usermod -a -G video wim

Where `video` is a group

Max on system:

> sysctl kernel.pid_max  # or:
> cat /proc/sys/kernel/pid_max

Limit per user:

> ulimit -Su   # Also -Hu; this is a shell internal command

Threads limit per user:

> sysctl kernel.threads-max

Show current threads per user:

> ps -L -u ec2-user

Port: localhost:631

Reset: sudo service cups restart

Disable authentication:

Change some things in your /etc/cups/cupsd.conf file:

• Change the authentication type to "None".
• Remove any lines that have "@SYSTEM" in it.
• Restart the CUPS daemon.

> find -name .directory -delete

Source

E.g.:

> ffmpeg -f x11grab -y -r 30 -s 1920x1080 -i :0.0 -vcodec huffyuv out.avi

Source - more useful commands there

> netstat -lntu

or

> ss -lntu

> sudo dhclient -r eth0    # release current lease
> sudo dhclient -r eth0    # Obtain fresh IP (didn't need it on olivia)

Following Does not work (any more) on latest debians Alternative: see restart network below

> sudo service bind9 restart    # also start|stop|status

Source, for RPi - works also for debian, see 'RPi only!' comments

Steps after edit:

> sudo systemctl daemon-reload               # RPi only! Debian doesn't need this
> sudo touch /etc/resolv.conf                # Rpi only: Apparently required to reset DNS
> sudo /etc/init.d/networking restart
> sudo ip addr del 192.168.1.16/24 dev eth0  # RPi only: previous IP still present, remove it

HOWEVER: DHCP ip's keep on popping back. Obviously, I missed something (disable DNS?) but I can't be bothered to look further.

• Hack: enable then disable wifi
• Check /etc/resolv.conf:

domain dynamic.ziggo.nl
search dynamic.ziggo.nl
nameserver 8.8.8.8
nameserver 8.8.4.4

Related: fork: retry: No child processes

• Check file descriptors: lsof gives way too many files, not clear how to filter. Doesn't seem to be the problem, though

Set `SUID` flag for Xorg binary.

When `startx` complains about not set. I.e. following happens:

...
Fatal server error:
(EE) xf86OpenConsole: VT_ACTIVATE failed: Operation not permitted
...
xinit: giving up
xinit: unable to connect to X server: Connection refused
xinit: server error
-------------------------------------------------------------------------------------------
xinit failed. /usr/bin/Xorg is not setuid, maybe that's the reason?

Solution:

> ls -l /usr/bin/Xorg
# expected permissions (note the s): '-rwsr-xr-x ...'
> chmod u+s /usr/bin/Xorg

Switch without stopping graphics:

• CTRL-ALT-F2 - F1..F6 all good
• CTRL-ALT-F7 - Back to graphics

Change the runlevel: Required for Xorg installs.

> sudo init 3    # stops graphics
> sudo init 5    # enables graphics

> usermod -a -G video wim

Howto: NVIDIA the hard way

• Follow ALL instructions up to 'Then restart your computer'.
• Follow all instructions installer throws at you, including interim restart.
• Don't forget `mkinitrd'!
• Needs to be redone on kernel update.

• Xpra - remote display server, allows (de)coupling) of apps to remote screens

• Some pi's don't start any more
  • pascale (pi1) is totally bricked
  • zombie (pi2) keeps on restarting
  • Perhaps they can't deal with latest raspbian, try older version? (TODO)
• Pi zero has different adapters for hdmi and power
  • Try remote setup with wifi (if possible)

• Default file manager raspbian hangs. Find new one?
• auto login to other user than `pi`
• setup backup

> sudo adduser wim 
> sudo usermod -aG sudo wim    # NB sudo for pi. Needs logout/login
> su - wim
> mkdir tmp

No sudo password Source

> sudo visudo

Add line at end:

username     ALL=(ALL) NOPASSWD:ALL

Change root password

• After you added new use with root (paranoia)
• Or disable root login entirely (TODO).

ssh

• ssh-keygen
• get public keys in order in all authorized_keys

• /etc/hosts, if necessary copy over existing from other machine, add current new one where necessary

Basic applications

Copy over:

> sudo apt-get install vim mc barrier ruby git vim-gtk locate
> sudo updatedb

• .vimrc
• .gitconfig
• .git-credentials

Add new machine to backups

See below

• Overview
• Uses RK3328 SoC
• Which contains a Mali-450 GPU

> sudo raspi-config

• Update firmware
• Set memory split for video

Only do this if required!

> sudo rpi-update

Can also be done with the RPi config tool:

link

NOTE: Takes a long time to complete, needs user interaction Best to reserve a day for this

• How to optimize Raspberry Pi code using its GPU
• Hacking The GPU For Fun And Profit (Pt. 4) - github
• Raspberry Pi VideoCore APIs
• GPGPU hacking on the Pi
• Accelerating Fourier transforms using the GPU
• Side libraries for interfacing to Raspberry Pi GPU
• GPU_FFT
• Macro assembler for Broadcom VideoCore IV aka Raspberry Pi GPU
• Errata VideoCore documentation
• Hermitage github - reference site for all things QPU

> sudo fsck -n /

Broken Corrupted Raspberry Pi SD Card - extensive list of things to try

• Main commands should also work on debian, will need init 1
• Following worked on rianne but not on pascale

> sudo su -
> mount   # to determine disk to repair, eg. /dev/sda1
> mount -o ro,remount /dev/sda1
> fsck.ext3 /dev/sda1

> sudo vi /boot/config.txt

Change section to following:

#uncomment to overclock the arm. 700MHz is the default
over_voltage=6   # Give little extra power
arm_freq=2000    # Max set frequency in MHz (may change dynamically due to temp throttling)
qpu_freq=750     # This is max, default 500MHz

Max Pi4:

arm_freq=2147

Pi3 needs `sudo` Clock frequencies variable, mostly due to throttling

> vcgencmd measure_clock arm   # Current clock frequency CPU
frequency(48)=750199232

> vcgencmd measure_clock core  # Current Clock frequency GPU
frequency(1)=333333984

> vcgencmd measure_temp
temp=47.0'C

> vcgencmd get_throttled       # Whether CPU throttled or not
throttled=0x0

Useful to combine with `watch`, eg:

> watch vcgencmd measure_clock arm   # Current clock frequency

It's easier to do this via raspi-config

The regular method with dpkg-reconfugre doesn't work on RPi. Following forces the issue:

> sudo vi /etc/default/local

#  File generated by update-locale
LANG=en_US.UTF-8
LC_ALL=en_US.UTF-8
LANGUAGE=en_US.UTF-8

• Set all to same desired locale (done here already), UTF-8 preferred
• works after restart
• As commented, this file is actually generated somewhere

NOTE: This will not work if the SD cards aren't perfect to begin with! I.e. dd gives 'input/output error' and aborts

Source

Following are for linux.

> sudo fdisk -l                            # To determine mount of SD card, eg `/dev/sdb` or `/dev/mmcblk0`
> sudo lsblk                               # Alternative to determine mounts
> sudo dd if=/dev/sdb of=stored_image.img  # To copy image to workstation disk

To restore:

> sudo dd if=stored_image.img of=/dev/sdb

Unfortunately, this happens and not much can be done about it.

Two things here:

1. RPi can damage SD cards, e.g. by bad voltage. The RPi1 I have seems prone to this
2. SD cards just plain go bad eventually, notably by many writes creating bad sectors

Despite this, the SD cards can still function properly:

1. 'Good' SD cards can circumvent bad blocks (internal OS)
2. You might get plain lucky and not hit the bad sectors

Issue here is that copying images with `dd` fails.

Conclusion: if you don't have a good card to begin with, best is to reinstall it from scratch

• Meaning, install must be made as painless as possible.
• And make frequent backups!

This is what I can remember from last, prob not complete and will be added to

• empty mail to auth-results@verifier.port25.com

Still gives following error:

----------------------------------------------------------
"iprev" check details:
----------------------------------------------------------
Result:         fail (no matching DNS records found)
ID(s) verified: policy.iprev=185.103.18.96

DNS record(s):
    96.18.103.185.in-addr.arpa. 300 IN PTR axizo-vps-2.cust.cj2.nl.
    axizo-vps-2.cust.cj2.nl. A (NXDOMAIN)

This is weird, because this is the provider's internal domain name. It is not specified anywhere in the test mail.

• DKIM Record Key Check

• Setup multiple domains

Required so to not have mail treated as spam in gmail

• Howto
• public key in DNS: Remove newlines and double quotes from public key

TODO verify

*NB:" Key type TEXT

I.e. Following public key:

mail._domainkey IN  TXT ( "v=DKIM1; h=sha256; k=rsa; "

: "p=MIIBIjA…t7mgj7A13tEBAs+V+" : "q8OW1D4Zb/iU6ypNTj…pKgU2wIDAQAB" ) ; –— DKIM key mail for axizo.nl

becomes in DNS record:

Key: mail._domainkey.axizo.nl

Value:  v=DKIM1; h=sha256; k=rsa; p=MIIBIjA...t7mgj7A13tEBAs+V+q8OW1D4Zb/iU6ypNTj...pKgU2wIDAQAB

• Make keys readable:

> cd /etc/opendkim/keys
> sudo chmod o+r -R .

• In /etc/opendkim.conf:

RequireSafeKeys false

Otherwise, error on send

• Restart:

> sudo service opendkim restart

(Using mailDir in postfix done in the flow)

sudo vi /etc/dovecot/conf.d/10-mail.conf:

mail_location = maildir:/home/%u/Maildir

Then:

> sudo service dovecot start

• Get PARTUUID and partition type

> sudo blkid
/dev/sda1: LABEL="Seagate Expansion Drive" UUID="E060D35060D32C52" TYPE="ntfs" PTTYPE="atari" \
PARTUUID="86750c0c-01"

• Add to fstab

> sudo vi /etc/fstab

Add (note path in /mnt, not /media:

PARTUUID=86750c0c-01 /mnt/extern ntfs    defaults,noatime  0       1

• Add to exports

> sudo vi /etc/exports

Add (<ip>/24 is access specifier for clients):

/mnt/extern   192.168.2.0/24(rw,sync,no_subtree_check)

• Then:

> sudo mount /mnt/extern
> sudo exports fs -ra                                     # restart nfs with new settings

> sudo mkdir -p /mnt/pi4-2/extern                         # ensure mount point exists
> sudo mount 192.168.2.126:/mnt/extern /mnt/pi4-2/extern  # ip of server

See files in ~/.config/autostart, use as template

• synergyc (in .bashrc
• emacs

These installs were adequate for initial startup. Further installs not noted here.

For emacs pdf output (needs pdflatex=):

Installed, consider uninstalling:

• gtk+3 (for meld - not working and removed)

• Still have issue with starting route, should be 192.168.1.1, i.e. not 0 at end Same solution applies
• sudo and wicd (!) needed restart to work
• /etc/wpa_supplicant.conf not needed for wifi; only for connect on command line. Consider removing.
• Not all stuff copied over from Downloads; backups still retained

Why so difficult???

Sources - Here if not used below, prune

• Install phpMyAdmin on Debian
• How To Install phpMyAdmin with Apache on Debian 10 (Buster)

Assume sudo for all:

apt install php7.3
apt install php7.3-cli php7.3-common php7.3-curl php7.3-mbstring php7.3-mysql php7.3-xml
apt install mariadb-server

• Follow instructions in this tutorial for download phpmyadmin
• For setup mariadb, use instructions here.
• Content /etc/apache2/conf-enabled/phpmyadmin.conf taken from this tutorial.
• And then some missing magic needs to be added to this file:

<Directory /user/share/phpmyadmin>
...
   Order allow,deny
   Allow from all
</Directory>

• Restart with: systemctl reload apache2

Source

Do not stop the mariadb service, as one tutorial said. mysqldump won't work otherwise.

sudo mysqldump -u root -p --all-databases > all_databases.sql

scp to other machine

sudo mysql -u root -p <  all_databases.sql

On batch AWS instances:

> sudo yum update

Resulted in:

Error: Package: libstdc++-devel-4.8.3-3.20.amzn1.noarch (@amzn-main)
           Requires: libstdc++48-devel = 4.8.3
           Removing: libstdc++48-devel-4.8.3-9.109.amzn1.x86_64 (@amzn-main)
               libstdc++48-devel = 4.8.3-9.109.amzn1
           Obsoleted By: gcc48-c++-4.8.5-28.142.amzn1.x86_64 (amzn-updates)
               libstdc++48-devel = 4.8.5-28.142.amzn1
           Available: gcc48-c++-4.8.5-11.135.amzn1.x86_64 (amzn-main)
               libstdc++48-devel = 4.8.5-11.135.amzn1
           Removing: gcc48-c++-4.8.3-9.109.amzn1.x86_64 (@amzn-main)
               Not found
           Updated By: gcc48-c++-4.8.5-28.142.amzn1.x86_64 (amzn-updates)
               libstdc++48-devel = 4.8.5-28.142.amzn1
Error: Package: libstdc++-devel-4.8.3-3.20.amzn1.noarch (@amzn-main)
           Requires: libstdc++48 = 4.8.3
           Removing: libstdc++48-4.8.3-9.109.amzn1.x86_64 (@amzn-main)
               libstdc++48 = 4.8.3-9.109.amzn1
           Updated By: libstdc++48-4.8.5-28.142.amzn1.x86_64 (amzn-updates)
               libstdc++48 = 4.8.5-28.142.amzn1
           Available: libstdc++48-4.8.5-11.135.amzn1.i686 (amzn-main)
               libstdc++48 = 4.8.5-11.135.amzn1
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

Resolved like this:

> sudo rpm -e libstdc++-devel-4.8.3-3.20.amzn1.noarch

• -e for 'erase'
• And redo sudo yum update

> sudo rcnscd restart

Olivia: via yast, DNS not working. Did following out of desperation:

> vi /etc/resolv.conf
nameserver 8.8.8.8
nameserver 8.8.4.4

After that, went OK (causal? There was no restart of anything required)

On local machine:

> cnf <exe-name>

Using zypper:

> sudo zypper wp <name>

> sudo zypper se --provides --match-exact <filename>

> cd ~/.local/share/Trash
> rm -rf files
> rm -rf info

texlive is bloody huge (~1GB); installing the full thing anyway

> sudo zypper in texlive
> sudo zypper in texlive-wrapfig

…and FINALLY it works

Also did this before:

> sudo zypper in texlive-latex-bin-bin
> sudo zypper install texlive-pdftex-bin
> sudo zypper install texconfig-bin

…but this didn't result in a working configuration

Source

"Try clicking both the left side and right side CTRL keys at the same time."

For when keys and/or mouse start acting funny.

In remote desktop type in shell:

setxkbmap

This is not actually meant for keyboard reset, but reset occurs as side effect.