Useful Linux commands

from here

# 1. redo last command but as root
sudo !!

# 2. open an editor to run a command
ctrl+x+e

# 3. create a super fast ram disk
mkdir -p /mnt/ram
mount -t tmpfs tmpfs /mnt/ram -o size=8192M

# 4. don't add command to history (note the leading space)
 ls -l

# 5. fix a really long command that you messed up
fc

# 6. tunnel with ssh (local port 3337 -> remote host's 127.0.0.1 on port 6379)
ssh -L 3337:127.0.0.1:6379 [email protected] -N

# 7. quickly create folders
mkdir -p folder/{sub1,sub2}/{sub1,sub2,sub3}

# 8. intercept stdout and log to file
cat file | tee -a log | cat > /dev/null

# bonus: exit terminal but leave all processes running
disown -a && exit

How To Install pgAdmin 4 on CentOS 7 / RHEL 7 & Fedora 29 / Fedora 28

Install pgAdmin 4

Once you have PostgreSQL repository configured on your system, run the following command to install pgAdmin 4.

### RHEL / CentOS ###

yum -y install pgadmin4

### Fedora ###

dnf -y install pgadmin4

Configure pgAdmin 4

We would need to do a few configuration changes prior to accessing the pgAdmin 4.

Copy the pgAdmin 4 sample configuration.

cp /etc/httpd/conf.d/pgadmin4.conf.sample /etc/httpd/conf.d/pgadmin4.conf

Create a pgAdmin log and data directories.

mkdir /var/log/pgadmin4/
mkdir /var/lib/pgadmin4/

Create/Edit config_local.py file.

vim /usr/lib/python2.7/site-packages/pgadmin4-web/config_local.py

Add the following settings. A

LOG_FILE = '/var/log/pgadmin4/pgadmin4.log'
SQLITE_PATH = '/var/lib/pgadmin4/pgadmin4.db'
SESSION_DB_PATH = '/var/lib/pgadmin4/sessions'
STORAGE_DIR = '/var/lib/pgadmin4/storage'

after the existing one:

import os
DATA_DIR = os.path.realpath(os.path.expanduser(u'~/.pgadmin/'))

Change permissions of directories so that Apache can write data into it. B

chown -R apache:apache /var/lib/pgadmin4/*
chown -R apache:apache /var/log/pgadmin4/*

Run the following command to create a user account for the pgAdmin 4 web interface. C

python /usr/lib/python2.7/site-packages/pgadmin4-web/setup.py

Output:

NOTE: Configuring authentication for SERVER mode.

Enter the email address and password to use for the initial pgAdmin user account:

Email address: [email protected]
Password: xxxxxxxxx
Retype password: xxxxxxxxx
pgAdmin 4 - Application Initialisation
======================================

Restart the Apache web service.

systemctl restart httpd

My https configuration file for Apache

For CentOS 7:

<VirtualHost *:80>
        ServerName pg.saic.it
        Redirect permanent / https://pg.saic.it/pgadmin4/
</VirtualHost>
<VirtualHost *:443>
        ServerName pg.saic.it
        LoadModule wsgi_module modules/mod_wsgi.so
        SSLEngine on
        SSLCertificateFile /etc/ssl/certs/pg.saic.it.crt
        SSLCertificateKeyFile /etc/ssl/certs/pg.saic.it.key
        SSLCACertificateFile /etc/ssl/certs/saic.sslforfree.ca
        WSGIDaemonProcess pgadmin processes=1 threads=25
        WSGIScriptAlias /pgadmin4 /usr/lib/python2.7/site-packages/pgadmin4-web/pgAdmin4.wsgi

        <Directory /usr/lib/python2.7/site-packages/pgadmin4-web/>
                WSGIProcessGroup pgadmin
                WSGIApplicationGroup %{GLOBAL}
                <IfModule mod_authz_core.c>
                        # Apache 2.4
                        Require all granted
                </IfModule>
                <IfModule !mod_authz_core.c>
                        # Apache 2.2
                        Order Deny,Allow
                        Deny from All
                        Allow from 127.0.0.1
                        Allow from ::1
                </IfModule>
        </Directory>
</VirtualHost>                

if you have this error in your Apache log file : Fatal Python error: PyEval_AcquireThread: NULL new thread state

is because mod_python have to removed from the modules

After the installation when you do an update the steps are: A, B, C

 

Use Let’s Encrypt for ssl certificate

From this web site follow the instructions to update your server web environment:

$ yum -y install yum-utils
$ yum-config-manager --enable rhui-REGION-rhel-server-extras rhui-REGION-rhel-server-optional
yum install certbot python2-certbot-apache

then run this for the website sample.lu

certbot -i apache -d sample.lu -d www.sample.lu --server https://acme-v02.api.letsencrypt.org/directory -a webroot --webroot-path=/var/www/sample.lu/web

this the result

Saving debug log to /var/log/letsencrypt/letsencrypt.log

Plugins selected: Authenticator webroot, Installer apache

Enter email address (used for urgent renewal and security notices) (Enter ‘c’ to

cancel): [email protected]

Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

Please read the Terms of Service at

https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf. You must

agree in order to register with the ACME server at

https://acme-v02.api.letsencrypt.org/directory

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

(A)gree/(C)ancel: A

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

Would you be willing to share your email address with the Electronic Frontier

Foundation, a founding partner of the Let’s Encrypt project and the non-profit

organization that develops Certbot? We’d like to send you email about our work

encrypting the web, EFF news, campaigns, and ways to support digital freedom.

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

(Y)es/(N)o: Y

Starting new HTTPS connection (1): supporters.eff.org

Obtaining a new certificate

Performing the following challenges:

http-01 challenge for sample.lu

http-01 challenge for www.sample.lu

Using the webroot path /var/www/sample.lu/web for all unmatched domains.

Waiting for verification…

Cleaning up challenges

Resetting dropped connection: acme-v02.api.letsencrypt.org

Deploying Certificate to VirtualHost /etc/httpd/conf/sites-enabled/100-sample.lu.vhost

Deploying Certificate to VirtualHost /etc/httpd/conf/sites-enabled/100-sample.lu.vhost

Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access.

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

1: No redirect – Make no further changes to the webserver configuration.

2: Redirect – Make all requests redirect to secure HTTPS access. Choose this for

new sites, or if you’re confident your site works on HTTPS. You can undo this

change by editing your web server’s configuration.

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

Select the appropriate number [1-2] then [enter] (press ‘c’ to cancel): 2

Redirecting vhost in /etc/httpd/conf/sites-enabled/100-sample.lu.vhost to ssl vhost in /etc/httpd/conf/sites-enabled/100-sample.lu.vhost

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

Congratulations! You have successfully enabled https://sample.lu and

https://www.sample.lu

You should test your configuration at:

https://www.ssllabs.com/ssltest/analyze.html?d=sample.lu

https://www.ssllabs.com/ssltest/analyze.html?d=www.sample.lu

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

IMPORTANT NOTES:

– Congratulations! Your certificate and chain have been saved at:

   /etc/letsencrypt/live/sample.lu/fullchain.pem

   Your key file has been saved at:

   /etc/letsencrypt/live/sample.lu/privkey.pem

   Your cert will expire on 2019-06-11. To obtain a new or tweaked

   version of this certificate in the future, simply run certbot again

   with the “certonly” option. To non-interactively renew *all* of

   your certificates, run “certbot renew”

– Your account credentials have been saved in your Certbot

   configuration directory at /etc/letsencrypt. You should make a

   secure backup of this folder now. This configuration directory will

   also contain certificates and private keys obtained by Certbot so

   making regular backups of this folder is ideal.

– If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let’s Encrypt:   https://letsencrypt.org/donate

   Donating to EFF:                    https://eff.org/donate-le