Sunday, April 26, 2020

Install Apache On Ubuntu Linux

Install the Apache web server on Ubuntu Linux. You will need to be able to install software and start services, so this example uses a Linux account with full sudo. In this example the Linux user name is "testuser".

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.4 LTS
Release:        18.04
Codename:       bionic


$ hostname -I
192.168.0.9


$ sudo ufw status
Status: inactive


# Update package list and install Apache.

$ sudo apt update
...
Fetched 2,854 kB in 2s (1,395 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.

$ sudo apt install apache2
...
Created symlink /etc/systemd/system/multi-user.target.wants/apache2.service → /lib/systemd/system/apache2.service.
Created symlink /etc/systemd/system/multi-user.target.wants/apache-htcacheclean.service → /lib/systemd/system/apache-htcacheclean.service.
...

# Note the screen output shows symlinks in the configuration directories for the system services.
 

# Let's see what was is running.
$ systemctl status apache2.service
● apache2.service - The Apache HTTP Server
   Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
  Drop-In: /lib/systemd/system/apache2.service.d
           └─apache2-systemd.conf
   Active: active (running) since Sun 2020-04-26 12:08:28 MDT; 2min 6s ago
 Main PID: 29916 (apache2)
    Tasks: 55 (limit: 4915)
   CGroup: /system.slice/apache2.service
           ├─29916 /usr/sbin/apache2 -k start
           ├─29918 /usr/sbin/apache2 -k start
           └─29919 /usr/sbin/apache2 -k start



# Use a web browser to go to the machine name or IP address.
# Earlier you found the IP address by typing "hostname -I".



# It is kind of the developers and package maintainers to make the home a set of instructions! 

# The instructions tell the path to index.html. Let's explore it.
$ cd /var/www/html
$ ls -l
total 12
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html

# Being owned by root, we can guess an "apache" unix logon was not created.
$ grep apa /etc/passwd
# Nothing found. Also look at last line of /etc/passwd for a new entry.
$ tail -1 /etc/passwd

# If software has errors, bugs, and security holes, and attacker may exploit those
# and possibly gain access as the user which is running the software.
# The apache software is being run as root. It had better be perfect software!
# Let's look further.

$ ps -ef | grep apache
root     29916     1  0 12:08 ?        00:00:00 /usr/sbin/apache2 -k start
www-data 29918 29916  0 12:08 ?        00:00:00 /usr/sbin/apache2 -k start
www-data 29919 29916  0 12:08 ?        00:00:00 /usr/sbin/apache2


# Processes are running both as root and as the pre-existing unix logon www-data.

# Let's see if www-data is a less-privileged account than root
$ groups www-data
www-data : www-data
$ sudo grep www /etc/sudoers

# No output from grep, so it looks like www-data doesn't have sudo. This is good.
# To open a listening connection on a "low numbered port", you typically need to be root.
# Maybe that is why part of the web server is started as root.
# This is something to further explore.

# For now, let's change the static web page served from the file index.html.
$ cd /var/www/html
$ ls -l
total 12
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
$ sudo cp index.html index.html.orig
$ ls -l
total 24
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
-rw-r--r-- 1 root root 10918 Apr 26 12:29 index.html.orig


# Edit the file and add some text.  When editing the file, search for "welcome" and change the text.
$ sudo vi index.html
# You may want to add text such as:
“I'm a greater believer in luck, and I find the harder I work the more I have of it.”
<a href="https://plato.stanford.edu/entries/jefferson">Thomas Jefferson</a>


# Reload your web browser to see your changes.



# Verify that systemctl is set up properly to start and stop the web server.
$ sudo systemctl stop apache2.service
$ ps -ef|grep apac
testuser       32236 28823  0 14:58 pts/0    00:00:00 grep apac


$ sudo systemctl start apache2.service
$ ps -ef | grep apac
root     32262     1  0 14:58 ?        00:00:00 /usr/sbin/apache2 -k start
www-data 32264 32262  0 14:58 ?        00:00:00 /usr/sbin/apache2 -k start
www-data 32265 32262  0 14:58 ?        00:00:00 /usr/sbin/apache2 -k start
testuser       32327 28823  0 14:58 pts/0    00:00:00 grep apac
$ systemctl status apache2.service
● apache2.service - The Apache HTTP Server
   Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
  Drop-In: /lib/systemd/system/apache2.service.d
           └─apache2-systemd.conf
   Active: active (running) since Sun 2020-04-26 14:58:53 MDT; 17s ago
  Process: 32214 ExecStop=/usr/sbin/apachectl stop (code=exited, status=0/SUCCESS)
  Process: 32242 ExecStart=/usr/sbin/apachectl start (code=exited, status=0/SUCCESS)
 Main PID: 32262 (apache2)
    Tasks: 55 (limit: 4915)
   CGroup: /system.slice/apache2.service
           ├─32262 /usr/sbin/apache2 -k start
           ├─32264 /usr/sbin/apache2 -k start
           └─32265 /usr/sbin/apache2 -k start

Saturday, April 18, 2020

Install Raspbian on Raspberry Pi B+

This will guide you through installation and configuration of a Raspberry Pi B+ with the Raspbian operating system so the device will be accessible on your network. Readily available for around $35, the Raspberry Pi ecosystem is fast-becoming a hobbyist workhorse.


Download Raspbian zip file from www.raspberrypi.org/downloads/raspbian. This example uses "Raspbian Buster with desktop" of February 2020.

Download the Etcher program from www.balena.io/etcher.  Etcher will write the OS zip file image to the SD card.

Insert an 8 GB (or more) microSD card in to the card reader on your Windows PC. This example uses a 32 GB card. In Windows Explorer you should see the SD card.
















Use the Etcher program to write the zip file OS image to the SD card.
 






























After writing the image, the SD card will be unmounted. Physically eject the card from your PC, then reinsert it. Determine the drive letter by looking in File Explorer.
















Let's tell the OS image to allow ssh login. Press the Windows Start button, type
cmd
and start the Command Prompt application.
In the command prompt, go to the drive letter of the SD card. In this example, type
F:

























Create a zero length file named ssh. In the command prompt, type
type nul > ssh



























If you will use a hard-wired ethernet connection from the device to your router, you will not need to configure wifi. To configure wifi, create a file named "wpa_supplicant.conf" with your wifi connection information. The file should only have the suffix ".conf" and the contents should not have Windows-like newline characters. It is important that newline characters are not added to this file. It should be a plain text file. Add the following to the wpa_supplicant.conf file.
country=US
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
scan_ssid=1
ssid="yourWifiSsid"
psk="yourWifiPassword"
}


Type exit to leave the command prompt.

In Windows File Explorer, right-click on the drive and choose EJECT. Physically eject the SD card from the PC.

Plug in the microSD card to the device, and insert the power connector cord in to the device. Don't yet plug it in to power.

Open your router configuration page, and look for the area which shows the current connections. You will looking for either a new DHCP client or a new MAC address. Now that you have opened your router configuration to the appropriate page, plug in the wall power for the device and turn on the power  switch.
Watch the router page for a new connection. If using wifi and it doesn't connect to the router, use the ethernet cable method. Note the IP address.


















Press the Windows Start button and open a command prompt. In the Windows command prompt, connect to the device using the IP address as seen in your router.
ssh pi@192.168.1.101
Accept the key fingerprint warning by typing yes.
The password is
raspberry

You should be logged in. Change the password.
$ passwd

















Modify settings such as locale language, host name, and maybe enable VNC. Start the handy configuration tool. I changed the locale and the host name.
$ sudo raspi-config

If wifi didn't work or you want to enable it, become root and edit the file.
$ sudo su
$ sudo vi /etc/wpa_supplicant/wpa_supplicant.conf


Reboot the device.
$ sudo reboot

The router page will show the new host name.

















For installation of an operating system on bare hardware, this was a smooth and pleasant experience. The teams who put together the custom OS and configuration tools have done superb!

Another good guide for how to install Raspbian OS is at Tom's Hardware.

Friday, April 17, 2020

Install PostgreSQL on Ubuntu Linux

# The documentation website of PostgreSQL is www.postgresql.org/docs.

$ sudo addgroup sql
[sudo] password for testuser:
Adding group `sql' (GID 1005) ...
Done.

$ sudo adduser pgsqlown --ingroup sql

$ sudo apt-get update
$ sudo apt-get upgrade


# For the software download, you may choose a more recent version of the database with the following section of this write-up, or skip ahead.
# If you want to install a more recent version:
$ sudo apt-get install curl ca-certificates gnupg
$ curl https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  4812  100  4812    0     0   4105      0  0:00:01  0:00:01 --:--:--  4105
OK


# Create /etc/apt/sources.list.d/pgdg.list with a line for the repository version for your Linux version.
$ lsb_release -c
Codename:       bionic
$ cat /etc/apt/sources.list.d/pgdg.list
deb http://apt.postgresql.org/pub/repos/apt/ bionic-pgdg main
$ sudo apt-get update
$ sudo apt-get install postgresql-11


# Use this for the quick install of whatever version is provided at the time of the Ubuntu release. Do one or the other of the prior install or the following install.
$ sudo apt install postgresql postgresql-contrib

# If you are watching /var/log/syslog during the install, you will see entries like:
Apr 16 22:19:16 dell990 systemd[1]: Starting PostgreSQL RDBMS...
Apr 16 22:19:16 dell990 systemd[1]: Started PostgreSQL RDBMS.
Apr 16 22:19:19 dell990 systemd[1]: Reloading.
Apr 16 22:19:19 dell990 systemd[1]: message repeated 2 times: [ Reloading.]
Apr 16 22:19:20 dell990 systemd[1]: Created slice system-postgresql.slice.
Apr 16 22:19:20 dell990 systemd[1]: Starting PostgreSQL Cluster 10-main...
Apr 16 22:19:22 dell990 systemd[1]: Started PostgreSQL Cluster 10-main.


$ ps -ef | grep sql
postgres  6118     1  0 22:19 ?        00:00:00 /usr/lib/postgresql/10/bin/postgres -D /var/lib/postgresql/10/main -c config_file=/etc/postgresql/10/main/postgresql.conf


# You should take a moment to review the config file.
$ more /etc/postgresql/10/main/postgresql.conf
$ grep -v ^\# /etc/postgresql/10/main/postgresql.conf | grep -v ^$ | grep -v $'\t'

# Note the install made the postgres user, with a home directory in /var/lib.
$ tail -1 /etc/passwd
postgres:x:122:123:PostgreSQL administrator,,,:/var/lib/postgresql:/bin/bash


# As configured, the postgres unix account does not allow a direct login, nor "su", because of the "*" (asterisk/star) in the second field of the actual password file.
$ sudo tail -1 /etc/shadow
postgres:*:18369:0:99999:7:::


# The software install made a unix group for the postgres user.
$ tail -1 /etc/group
postgres:x:123:


# All of the running processes for the database owner.
$ ps -fu postgres
UID        PID  PPID  C STIME TTY          TIME CMD
postgres  6118     1  0 22:19 ?        00:00:00 /usr/lib/postgresql/10/bin/postgres -D /var/lib/postgresql/10/main -c config_file=/etc/postgresql/10/main/postgresql.conf
postgres  6128  6118  0 22:19 ?        00:00:00 postgres: 10/main: checkpointer process
postgres  6129  6118  0 22:19 ?        00:00:00 postgres: 10/main: writer process
postgres  6130  6118  0 22:19 ?        00:00:00 postgres: 10/main: wal writer process
postgres  6131  6118  0 22:19 ?        00:00:00 postgres: 10/main: autovacuum launcher process
postgres  6133  6118  0 22:19 ?        00:00:00 postgres: 10/main: stats collector process
postgres  6135  6118  0 22:19 ?        00:00:00 postgres: 10/main: bgworker: logical replication launcher

# Note the line with PID 6118. That started the database server and shows the configuration file.

# The software install may have been placed in /usr/share.
$ ls -ld /usr/share post*
drwxr-xr-x   3 root root  4096 Apr 16 22:19 postgresql
drwxr-xr-x   5 root root  4096 Apr 16 22:19 postgresql-common
drwxr-xr-x 253 root root 12288 Apr 16 22:19 /usr/share


# Check if automatic database startup was configured with systemctl. Looks like it was not configured, as there are no new files in /etc/systemd/system.
$ ls -ltr /etc/systemd/system

# Yet there is a systemctl entry.
$ systemctl status postgresql
● postgresql.service - PostgreSQL RDBMS
   Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor preset: enabled)
   Active: active (exited) since Thu 2020-04-16 22:19:16 MDT; 1 day 1h ago
 Main PID: 5093 (code=exited, status=0/SUCCESS)
    Tasks: 0 (limit: 4915)
   CGroup: /system.slice/postgresql.service
 

# It is running from systemctl, so look further for systemctl files.
$ sudo grep -i post /etc/systemd/system/*/* 2>/dev/null
/etc/systemd/system/multi-user.target.wants/postgresql.service:# systemd service for managing all PostgreSQL clusters on the system. This
/etc/systemd/system/multi-user.target.wants/postgresql.service:Description=PostgreSQL RDBMS


# Check if jobs were added in cron. Can we "su" to login to the new account... Is there a password for the user?
$ sudo grep postgres /etc/shadow
postgres:*:18369:0:99999:7:::

# The second field has an asterisk (*), so it is not possible to "su" and enter a password.

# Let's use sudo to become the user and look for a crontab entry.
$ sudo su - postgres
postgres@dell990:~$ id
uid=122(postgres) gid=123(postgres) groups=123(postgres),112(ssl-cert)
postgres@dell990:~$ crontab -l
no crontab for postgres

# We have determined nothing is configured cron, and the database start and stop is configured in systemctl.

# Let's try to log in with the sql interpreter, and then log out.
$ psql
psql (10.12 (Ubuntu 10.12-0ubuntu0.18.04.1))
Type "help" for help.
postgres=# \q

# Exit the sql interpreter with "\q" and press ENTER.

# Confirm which version of the database we are connecting to. Press "q" when you have finished reading the output from the SELECT command.
$ psql
psql (10.12 (Ubuntu 10.12-0ubuntu0.18.04.1))
Type "help" for help.
postgres=# select version();
                                                                version                                                
----------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 10.12 (Ubuntu 10.12-0ubuntu0.18.04.1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0, 64-bit
(1 row)

(END)                                                                version                                           
----------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 10.12 (Ubuntu 10.12-0ubuntu0.18.04.1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0, 64-bit
(1 row)

(END)           


# Another way to show the database software version while in the sql interpreter.
postgres=# show server_version;
            server_version
---------------------------------------
 10.12 (Ubuntu 10.12-0ubuntu0.18.04.1)
(1 row)


# We can also ask the postgres executable which version it is.
$ postgres -V
Command 'postgres' not found, did you mean:
  command 'postgrey' from deb postgrey
Try: apt install <deb name>


# Confirm we are using the unix login of the software owner, and look at the PATH environment variable.
$ whoami
postgres
$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin


# Find where "postgres" was installed in the filesystem.
$ sudo find / -name postgres -print 2>/dev/null
/run/sudo/ts/postgres
/usr/lib/postgresql/10/bin/postgres


# The directory in that second line of output should be added to our PATH shell environment variable. Add just the directory path, not the actual "postgres" command.
$ echo 'export PATH=$PATH:/usr/lib/postgresql/10/bin' >> /var/lib/postgresql/.bashrc

# Login again, or "source" the login file. Type this in the "home" directory.
$ . ./.bashrc

# Check the new setting of PATH shell environment variable.
$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/lib/postgresql/10/bin/postgres:/usr/lib/postgresql/10/bin


# Try the version command again.
$ postgres -V
postgres (PostgreSQL) 10.12 (Ubuntu 10.12-0ubuntu0.18.04.1)


# Log in and find out which role is in use. In this case, it is the same as the unix login.
$ psql
psql (10.12 (Ubuntu 10.12-0ubuntu0.18.04.1))
Type "help" for help.

postgres=# \conninfo
You are connected to database "postgres" as user "postgres" via socket in "/var/run/postgresql" at port "5432".


# List table names in this database. In this case, there are none.
postgres=# \d
Did not find any relations.



### Use PostgreSQL perl wrapper to determine what is running. Similar, though different than the earlier "ps" command.
$ pg_lsclusters
Ver Cluster Port Status Owner    Data directory              Log file
10  main    5432 online postgres /var/lib/postgresql/10/main /var/log/postgresql/postgresql-10-main.log
 

$ pg_ctlcluster 10 main status
pg_ctl: server is running (PID: 6118)
/usr/lib/postgresql/10/bin/postgres "-D" "/var/lib/postgresql/10/main" "-c" "config_file=/etc/postgresql/10/main/postgresql.conf"

# Stop the server. You may want to simultaneously run unix "top" in another window to watch the process.
# While you can use pg_ctlcluster with "stop", you should use the already-configured systemctl.


### Set up a backup. This is a client program which may be run from a different machine.
$ which pg_dumpall
/usr/bin/pg_dumpall


# The command to backup all databases should run quickly because nothing has been added yet.
$ pg_dumpall > /tmp/postgres.backup

# The curious may want to look at the backup file.
$ file /tmp/postgres.backup
/tmp/postgres.backup: ASCII text
$ more /tmp/postgres.backup

--
-- PostgreSQL database cluster dump
--

... and the backup file continues and ends with ...
--
-- PostgreSQL database cluster dump complete
--


# Add the following line in unix user postgres crontab.
$ crontab -l
* 1 * * * /usr/lib/postgresql/10/bin/pg_dumpall > /tmp/postgres.backup.$(/bin/date +%Y%m%d.%H%M%S) 1>>/tmp/postgres.cron 2>>&1

Sunday, April 12, 2020

VNC On Ubuntu Linux

How to set up VNC (virtual network computing) on Ubuntu Linux and Microsoft Windows 10 to transport an X display over a network. This will allow you to connect "X" graphical displays across machines so you can run a program on Linux and view the program graphical display on Microsoft Windows PC. This example sets up a direct VNC connection, which is not secure. Once these examples are in place and working, you can configure the VNC connection to go through an SSH tunnel. Let's go one step at a time, and start with a plain VNC connection.

This example uses TightVNC from www.tightvnc.com/download.php and sourceforge.net/projects/vnc-tight.

In these examples, the lines that begin with a $ (dollar sign) indicate you should type what is after the dollar sign in to your Linux command prompt. Do not type the leading dollar sign.


### For first time setup on the Linux machine, have your system adminstrator install the packages.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.4 LTS
Release:        18.04
Codename:       bionic


$ uname -a
Linux dell990 4.15.0-96-generic #97-Ubuntu SMP Wed Apr 1 03:25:46 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux


# System administrator should add this line to end of /etc/apt/sources.list "deb http://mirrors.kernel.org/ubuntu bionic main universe"
$ grep mirrors /etc/apt/sources.list
deb http://mirrors.kernel.org/ubuntu bionic main universe


# System administrator should install the VNC package. Also install xterm.
$ sudo apt update
$ sudo apt install tightvncserver
$ sudo apt install xterm



### As the user of VNC on the Linux machine, do the following.
# Log in to Linux. In your Linux home directory, create the password file (~/.vnc/passwd) by running the vncpasswd program.
# From Windows, press the Start button, type cmd, and open a command prompt. In the Windows PC command prompt type "ssh testuser@ip_address" and log in to your Linux account.
# Press the Start button, type "cmd", and open a command prompt.
# In the command prompt window, using your user name, type: ssh testuser@ip_address
# For the first ssh connection, accept the ssh key fingerprint if you are prompted. Your system administrator will tell you the account name (testuser in this example) and the IP address or host name (192.168.1.9 in this example).



















# Once you are logged in to the Linux machine, set up your VNC password. You only need to do this one time.
$ vncpasswd
Using password file /home/testuser/.vnc/passwd
VNC directory /home/testuser/.vnc does not exist, creating.
Password:
Warning: password truncated to the length of 8.
Verify:
Would you like to enter a view-only password (y/n)? n


# Start the VNC server on the Linux machine.
$ vncserver
xauth:  file /home/testuser/.Xauthority does not exist
New 'X' desktop is dell990:1
Creating default startup script /home/testuser/.vnc/xstartup
Starting applications specified in /home/testuser/.vnc/xstartup
Log file is /home/testuser/.vnc/dell990:1.log

# Note the display number is "1".
# Remember in this example, the IP address is 192.168.1.9. Your IP or hostname is likely different than this example.


# The VNC server is running as a process with your username and is listening for an incoming connection.
$ ps -ef | grep vnc
testuser  6312     1  0 20:24 pts/1    00:00:00 Xtightvnc :1 -desktop X -auth /home/testuser/.Xauthority -geometry 1024x768 -depth 24 -rfbwait 120000 -rfbauth /home/testuser/.vnc/passwd -rfbport 5901 -fp /usr/share/fonts/X11/misc/,/usr/share/fonts/X11/Type1/,/usr/share/fonts/X11/75dpi/,/usr/share/fonts/X11/100dpi/ -co /etc/X11/rgb




# On your PC, download the VNC viewer from www.tightvnc.com/download.php.  If your Windows PC has 4GB of RAM or less, you probably will choose the 32-bit version.
# You only need the viewer. Choose the CUSTOM setup and install the viewer.


















# On the Windows PC, run the TightVNC viewer app. Make the remote host the Linux machine with two colons and the VNC display number. In this example, it is 192.168.1.9:11.

















# Press "Connect" and it will open a TightVNC Viewer window on the Windows PC. At this point, the VNC Viewer window is like an empty display container.


















# If you try to run a graphical program on the Linux machine, it likely will not work. For example:
$ xterm
PuTTY X11 proxy: unable to connect to forwarded X server: Network error: Connection refused
xterm: Xt error: Can't open display: localhost:10.0
$ echo $DISPLAY
localhost:10.0
$ echo $TERM
xterm


# It likely didn't work because the Linux machine needs to know where to send the display output. This is set in your Linux shell environment variable DISPLAY. Type the following in the Linux shell. The number "1" is used in this example because that was the number from the earlier "vncserver" command.
$ export DISPLAY=localhost:1
$ echo $DISPLAY
localhost:1


# If the Linux shell environment variable TERM is not set to "xterm" or similar, do that now.
$ export TERM=xterm

# Test the clock program to display the output in the VNC Viewer on your Windows PC by running the clock program in the Linux shell. In the Linux shell type "xclock".
$ xclock


















# Switch back to your Linux shell. You should notice that you can't type anything; it is not accepting input. Press the ENTER key a few times to test this.

# In the Linux shell, press CTRL-c to end the clock program. The clock in the VNC Viewer on your PC should close.

# Try to run the clock again. This time, put an & (ampersand) after the command. The clock should display, the shell will show the process ID (PID) of the clock process, and you will also be able to type in the Linux shell.
$ xclock &
[1] 10904


# Open a new shell window and display it in the VNC Viewer app on your Windows PC.
$ xterm &
[2] 10907


# In the new shell window which is displayed on the PC, type a quick command. Ensure your Windows PC mouse is over the window where you want to type.
$ uname -a
Linux dell990 4.15.0-96-generic #97-Ubuntu SMP Wed Apr 1 03:25:46 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux


# In the window on your PC, type "exit". It should disappear. Go back to your first Linux connection and press ENTER. The shell should tell you that process has ended.
$
[2]+  Done                    xterm

# End the clock program. In Linux use the "kill" command with the process ID (PID) that it displayed when you started the clock program. The press ENTER again and the Linux shell will tell you the process has terminated.
$ kill -term 10904
testuser@dell990:~$
[1]+  Terminated              xclock


# Start a web browser on the Linux machine and it will display in the VNC Viewer on your Windows PC.
$ firefox &
[1] 10959

# In the web browser that should have appeared in the VNC viewer, go to a website which shows the IP address. The IP address will be the public facing IP address of the Linux machine, not the IP address of your Windows PC.



















# When using an xterm window, try pressing CTRL+leftMouseButton to show an options menu.

# You should be able to close the Linux terminal session and still have the programs displayed in VNC on the PC continue to run.

# To completely stop the VNC server, on the Linux machine type:
$ vncserver -kill :1
Killing Xtightvnc process ID 503



# Customize the window settings by creating file .Xresources in your home directory. Then kill and restart the vncserver.
$ cat .Xresources
! Type "man xterm" for all settings.

! Set window size.
XTerm.vt100.geometry: 80x32
XTerm.vt100.reverseVideo: true

! Type "fc-list :scalable=true: family | sort | more" to show available fonts.
! Set a font and size.
XTerm.vt100.faceName: Ubuntu Mono:size=12:antialias=false
XTerm.vt100.faceSize: 12

! Double-click selects whole word.
XTerm.VT100.charClass: 33:48,35-37:48,43:48,45-47:48,64:48,126:48

! Scroll bar on right side. Use left or right mouse button on top of scroll bar to move it.
XTerm.vt100.scrollBar: true
XTerm.vt100.rightScrollBar: true
XTerm.vt100.scrollbar.width: 8
XTerm.vt100.saveLines: 2048

! Allow window resize.
XTerm.vt100.allowWindowOps: true


Friday, April 10, 2020

After-Install Setup Tasks On Ubuntu 18

After Ubuntu 18 is running, you may want to do additional setup: setup a group and user, set colors, configure a firewall, setup dynamic DNS, and remove unused packages and services.


### Which version of the operating system. Also use "uname -a".
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.4 LTS
Release:        18.04
Codename:       bionic



### Become familiar with what is booting and running by watching the system log.
$ sudo tail -f /var/log/syslog


### Modify the shell login files in your home directory.
$ cd ~
$ cp -p .bashrc .bashrc.orig
$ mv .profile .profile.orig
$ mv .bashrc .bash_profile

### Set a default editor.
# Choose your editor
$ select-editor
# The editor may be set in your login files.
export EDITOR=vi

### Remove colorization.
# Using your file editor (such as vi) comment out all of the code with "color".
$ vi .bash_profile

# Also, put the present working directory at the end of the PATH variable by adding to end of file .bash_profile
export PATH=$PATH:.

# Log in again. Alternatively, "source" your logon file.
$ . ./.bash_profile


### Remove software until you are ready to use it
$ sudo apt-get remove openvpn
$ sudo systemctl disable openvpn
Synchronizing state of openvpn.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install disable openvpn
Unit /etc/systemd/system/openvpn.service is masked, ignoring.
# Then disable the openvpn startup file
$ cd /etc/default
$ sudo mv openvpn openvpn.20170702


### Alternatively, find and disable services you may not be using
$ systemctl list-units --all --type=service --no-pager
# Some services you may want to disable are
 cups-browsed.service  loaded  active  running Make remote CUPS printers
 cups.service          loaded  active  running CUPS Scheduler
 ModemManager.service  loaded  active  running Modem Manager

# Check the service, stop the service, then disable the service
$ systemctl status cups-browsed
 cups-browsed.service - Make remote CUPS printers available locally
   Loaded: loaded (/lib/systemd/system/cups-browsed.service; enabled; vendor preset: enabled)
   Active: active (running) since Sun 2020-04-05 00:05:14 MDT; 14h ago
 Main PID: 21137 (cups-browsed)
    Tasks: 3 (limit: 4915)
   CGroup: /system.slice/cups-browsed.service
           └─21137 /usr/sbin/cups-browsed
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

$ sudo systemctl stop cups-browsed
$ sudo systemctl disable cups-browsed
$ sudo systemctl stop cups
$ sudo systemctl disable cups
$ sudo systemctl stop ModemManager
$ sudo systemctl disable ModemManager

# After the next machine restart, verify the services are not runing.
$ sudo reboot
 

#  Or alternatively use systemctl to restart the machine.
$ sudo systemctl reboot
$ systemctl list-units --all --type=service --no-pager


# Another example of disabling a service, for the Let's Encrypt https certbot service.
$ systemctl status certbot.service
● certbot.service - Certbot
   Loaded: loaded (/lib/systemd/system/certbot.service; static; vendor preset: enabled)
   Active: inactive (dead) since Fri 2020-04-10 16:43:44 MDT; 5h 40min ago
     Docs: file:///usr/share/doc/python-certbot-doc/html/index.html
           https://letsencrypt.readthedocs.io/en/latest/
 Main PID: 31598 (code=exited, status=0/SUCCESS)
$ sudo systemctl stop certbot
Warning: Stopping certbot.service, but it can still be activated by:
  certbot.timer
$ sudo systemctl disable certbot



### When you log on you will see messages about software updates.
38 packages can be updated.
34 updates are security updates.

$ Install the software updates.
$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get dist-upgrade


$ When you next logon, the upgrade counter should drop. Not all can take effect until after a reboot.
0 packages can be updated.
0 updates are security updates.
*** System restart required ***
$ sudo shutdown -r



### Setup a user and group. In this example, the new users is "testuser" and the new group is "minec".
$ sudo addgroup minec
$ cat /etc/group | grep minec

# Create new user.
$ sudo adduser testuser --ingroup minec
# At this point, you may want to log in as the user and run command "groups" to confirm the group is set up appropriately.

# Allow logon via ssh. Put user in /etc/ssh/sshd_config on the "AllowUsers" line
# Use "vi" or "vim" or similar editor to edit file /etc/ssh/sshd_config and add "testuser" to the "AllowUsers" line.
# After editing, it will look like this:
$ grep -i allowusers /etc/ssh/sshd_config
AllowUsers testuser
# You may want to review the security implications of the following settings in sshd_config:
# Protocol, PermitRootLogin, AuthorizedKeysFile, PermitEmptyPasswords
# IgnoreRhosts, PermitTunnel, ciphers.
$ grep -i ^permitrootlogin /etc/ssh/sshd_config
PermitRootLogin no


# Have ssh  reread the configuration file. First get the process ID, then send HUP signal to that PID.
$ ps -ef | grep 'bin/sshd'$ sudo kill -hup <sshd_pid>
# Alternatively use service manager to restart ssh
$ sudo systemctl restart ssh

# View the effective settings of sshd
$ sshd -T

# Maybe put testuser in sudoers. Careful with this, as it provides root access.
$ sudo usermod -aG sudo testuser

# Maybe modify defaults of sudo
$ sudo visudo


### Configure firewall
# "Uncomplicated FireWall", known as ufw, should already be installed. If not, run:
$ sudo apt install ufw
# Ensure the filtering of IPv6 firewall is on, even if you are not using IPv6 at this time
$ sudo vi /etc/default/ufw
# Ensure this line exists without a leading comment character:
$ IPV6=yes
# Setup ufw services
$ sudo ufw allow ssh
$ sudo ufw allow http
$ sudo ufw allow https

# Deny outgoing SMTP mail
$ sudo ufw deny out 25

# Consider a block on geographic network address ranges.
# Look at the ufw settings
$ sudo ufw status numbered
$ sudo ufw enable
$ sudo ufw status



### If you have a changing IP (typical consumer-grade internet) and want to more easily host an incoming service, setup up dynamic DNS. Go to www.duckdns.org and configure a sub-domain for your host. Using the information from your sign up at duckdns.org, configure the following on the Linux machine.
$ cat /var/opt/duckdns/duck.sh
#!/bin/sh
DOMAINFQ="YOUR_DOMAIN.duckdns.org"
curl_out=$(echo url="https://www.duckdns.org/update?domains=YOUR_DOMAIN&token=YOUR_TOKEN" | /usr/bin/curl --insecure --silent --config - )
# Whatever is running this script (cron?) may want to direct output to a file in /tmp.
/bin/echo
/bin/date
/bin/echo duckdns updated $curl_out
/bin/echo 'dig output:'
/usr/bin/dig $DOMAINFQ | /bin/grep ^$DOMAINFQ
if [ $curl_out = "OK" ]; then
    /usr/bin/logger -p daemon.info "duckdns update ok. rc=" $curl_out
else
    /usr/bin/logger -p daemon.err "duckdns update failed. rc=" $curl_out
fi


# Run script every ten minutes from cron. Add this line to the crontab.
$ crontab -e
*/10 * * * * /var/opt/duckdns/duck.sh >>/tmp/duckdns.log 2>&1




### When you logon, the message displayed is from motd.dynamic.
$ ls -l /run/motd.dynamic
-rw-r--r-- 1 root root 753 Apr 11 17:58 /run/motd.dynamic


# If you do not yet have data backups configured, add a message to your users.
$ sudo vi /etc/update-motd.d/60-backup-warning
$ sudo chmod +x /etc/update-motd.d/60-backup-warning
# Add the following lines to this new file.
$ cat 60-backup-warning
#!/bin/sh
printf "\n"
printf "*** Warning: This machine is not on regular backups. Plan accordingly.\n"


# Consider disabling the live patch message, and others. Remove the execute permission.
$ sudo chmod -x /etc/update-motd.d/80-livepatch
$ sudo chmod -x /etc/update-motd.d/10-help-text



Sunday, April 05, 2020

Minecraft Setup On Linux Using systemctl

With schools and the economy shut down, all the cool kids are talking about their Minecraft "server" and the "IP. Help your children be cool and get them a Minecraft server!


In this posting we will:
- set up unix group and user
- configure ssh
- install Minecraft software
- start and configure Minecraft to run as a unix service (daemon)


$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.4 LTS
Release:        18.04
Codename:       bionic



### Setup a user and group. In this example, the new users is "testuser" and the new group is "minec".
$ sudo addgroup minec
$ cat /etc/group | grep minec

# Create new user for the software install.
$ sudo adduser minec --ingroup minec
# At this point, you may want to log in as the user and run command "groups" to confirm the group is set up appropriately.

# Allow logon via ssh. Put user in /etc/ssh/sshd_config on the "AllowUsers" line
# Use "vi" or "vim" or similar editor to edit file /etc/ssh/sshd_config and add "testuser" to the "AllowUsers" line.
# After editing, it will look like this:
$ grep -i allowusers /etc/ssh/sshd_config
AllowUsers minec

# Have ssh  reread the configuration file. First get the process ID, then send HUP signal to that PID.
$ ps -ef | grep 'bin/sshd'$ sudo kill -hup <sshd_pid>
# Alternatively use service manager to restart ssh
$ sudo systemctl restart ssh


### If java is not installed, install java now.
$ which java
$ sudo apt update
Hit:1 http://archive.ubuntu.com/ubuntu focal InRelease
Get:2 http://archive.ubuntu.com/ubuntu focal-updates InRelease [107 kB]
Get:3 http://archive.ubuntu.com/ubuntu focal-backports InRelease [98.3 kB]
Get:4 http://archive.ubuntu.com/ubuntu focal-security InRelease [107 kB]
Fetched 312 kB in 1s (252 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
$ sudo apt install openjdk-11-jdk

...
$ which java
/usr/bin/java



### Install Minecraft.
# Good instructions are at minecraft.gamepedia.com/Tutorials/Setting_up_a_server
# After downloading the software, the directory structure will look like this.
$ pwd
/home/minec/Minecraft_Server
$ ls -l
total 35368
-rw-r-----  1 minec minec        2 Apr  4 12:56 banned-ips.json
-rw-r-----  1 minec minec        2 Apr  4 12:56 banned-players.json
-rw-r-----  1 minec minec      180 Mar 29 19:21 eula.txt
drwxr-x---  2 minec minec     4096 Apr  5 09:55 logs
-rw-r-----  1 minec minec      140 Apr  4 12:56 ops.json
-rw-r-----  1 minec minec 36175593 Mar 29 19:01 server.jar
-rw-r-----  1 minec minec      940 Apr  4 12:56 server.properties
-rwxr-x---  1 minec minec       67 Apr  4 10:01 startminecraft.sh
-rw-r-----  1 minec minec     1645 Apr  5 16:13 usercache.json
-rw-r-----  1 minec minec        2 Mar 29 19:21 whitelist.json
drwxr-x--- 11 minec minec     4096 Apr  5 17:46 world


# In preparation for starting the server unattended, the startup commands are in the executable shell file "startminecraft.sh".
This script first backs up the Minecraft configuration.
If you want to run it from the console and watch the log in the GUI, run the java command without "-nogui".
#!/bin/sh
umask 026
cd /home/minec/Minecraft_Server
/bin/tar -cvf /tmp/worldDirs.$(date +%Y%m%d.%H%M%S).tar /home/minec/Minecraft_Server/world
echo "Finished tar of worldDirs."
/usr/bin/java -jar /home/minec/Minecraft_Server/server.jar -nogui &
/bin/echo $! > /home/minec/Minecraft_Server/minecraft.service.pid


# Set up the service. Create file /etc/systemd/system/minecraft.service with these contents.
$ cd /etc/systemd/system
$ sudo vi minecraft.service
[Unit]
Description=Minecraft server
After=network.target
[Service]
User=minec
Group=minec
ExecStart=/home/minec/Minecraft_Server/startminecraft.sh
#PIDFile=/var/run/minecraft.service.pid
#ExecStop=/bin/kill -s TERM $MAINPID
KillMode=process
Restart=on-failure
Type=forking
TimeoutStartSec=120
TimeoutStopSec=30
RuntimeMaxSec=infinity
[Install]
WantedBy=multi-user.target


# Reload systemctl configurations.
$ sudo systemctl daemon-reload
# Enable the service.
$ sudo systemctl enable minecraft.service
Created symlink /etc/systemd/system/multi-user.target.wants/minecraft.service → /etc/systemd/system/minecraft.service.

# If the prior line output is not "Created symlink ..." then something is not correct.

# Start the minecraft service.
$ sudo systemctl enable minecraft.service
$ sudo systemctl start minecraft.service

$ sudo systemctl status minecraft.service


# Restart the machine to test if the Minecraft server starts ok.
$ sudo reboot

# After the machine restarts, look in /var/log/syslog for messages, check the status of the service, and look for the process.
$ sudo tail -44 /var/log/syslog
$ ps -ef | grep mine


$ systemctl status minecraft.service
● minecraft.service - Minecraft server
   Loaded: loaded (/etc/systemd/system/minecraft.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2020-04-10 21:26:31 MDT; 3min 26s ago
  Process: 7622 ExecStart=/home/minec/Minecraft_Server/startminecraft.sh (code=exited, status=0/SUCCESS)
 Main PID: 7632 (java)
    Tasks: 36 (limit: 4915)
   CGroup: /system.slice/minecraft.service
           └─7632 /usr/bin/java -jar /home/minec/Minecraft_Server/server.jar -nogui