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PostgreSQL in Manjaro Linux
Date: 2015-11-03 07:43:53 +0000
First, I’m using a Manjaro Linux, an Arch-based Linux distro, where I wanted to run a PostgreSQL 9.4.5 local database for development.
- Database Server Setup
- PostgreSQL Version
- Connecting to the Database
Database Server Setup
User postgres
The trouble I got into is when logging in as user postgres . I have read somewhere that this is related to my package manager and/or to keep PostgreSQL safe. I do not have the link where I read it but for now I’ll skip it and return later to add the information here.
The first I found was how to become the postgres user without being asked for the postgres user password (because I don’t know the password). First become the root before becoming postgres (link here).
The last command brought me to /var/lib/postgres .
Database Initialization
The following command initializes the database storage area on disk; also called database cluster in PostgreSQL and catalog cluster in the SQL standard (PostgreSQL 9.4.5 Documentation §17.2).
The directory /var/lib/postgres/data is called data directory or data area. PostgreSQL documentation says that the command must be executed while logged as PostgrSQL user account which is the reason I needed to do the first step above.
Starting the Database Server
The database server application is postgres . The user must supply the initialized database cluser as a parameter.
To terminate the above process, press Ctrl+C .
The following command to run the database server in the background as suggested in the documentation produces an error. (More information about this in an update).
The database server may be started using systemctl . It runs the database server in the background so there is no need to keep an open console as when using the postgres command.
Stopping the Database Server
The corresponding command to stop a running database server is
Check Status of PostgreSQL Server
PostgreSQL has a utility that checks the connection status of a PostgreSQL server.
When the server has not been started the utility will have the following output.
PostgreSQL Version
There are a number of ways to check the PostgreSQL version information; through the commandline and inside the PostgreSQL client application.
Commandline Interface
One can check the PostgreSQL version from the operating system commandline interface.
Server version
Client version
psql Interface
One can also query the database version from the PostgreSQL commandline client application. The database server must be running and one must be connected to it.
SELECT version()
server_version
server_version_num
Connecting to the Database
pgAdmin Application
pgAdmin 1.20..0. Using pgAdmin3 to create a database requires that the database server is running.
Create a server from the menu File | Add Server and the New Server Registration window will prompt the user for information.
There are four (4) tab pages but focus will be in the Properties tab page. The Properties tab page have these information among others that will be useful when connecting to a database:
- Name — name of the server
- Host — host to connect to (or localhost)
- Port — port to connect to (default is 5432)
- Username
- Password
Creating a new server automatically creates a default database named postgres .
I can connect to the database server from the commandline.
Check the current logged in user.
Terminate the commandline session by typing \quit . See https://www.postgresql.org/docs/9.2/static/app-psql.html for other psql arguments.
Server Instrumentation
If prompted to install the server instrumentation, just use the create extension command:
The command will install the adminpack extensionn that is found in /usr/share/postgresql/extension .
Create Group Role
Create group and user role. Make the user able to connect to the database.
One can also connect to the database via ODBC. UnixODBC 2.3.4 was released on 31 August 2015 and is available in Manjaro Linux. This link talks about ODBC in Arch Linux.
Display the contents of odbc.ini file.
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How to Check that PostgreSQL Server is Running on Linux (Ubuntu/Debian/Red Hat/Fedora)
This tutorial will show you how to check that the PostgreSQL Server service is running on your Linux system.
Checking PostgreSQL is Running on Ubuntu/Debian
To check whether the PostgreSQL server service is running successfully on your Debian or Ubuntu system, run:
Checking the Firewall
By default PostgreSQL runs on port 5432 and is not restricted by host name.
When installing PostgreSQL on Ubuntu, usually a firewall rule will be created automatically allowing access to the database server.
You can confirm this by running the nmap command:
This will show the ports and service that are open on your machine – check through the list and make sure that postgresql is listed next to the port number 5432.
If it is not listed, you can open the firewall port using the ufw command:
If you have configured different a different hostname or port from the default, you may need to update your firewall rules to match.
Checking PostgreSQL is Running on Arch Linux
The process to check whether PostgreSQL is running is the same on Arch Linux, simply run:
Checking the Firewall
Again, the nmap command is useful here for checking that the default PostgreSQL port of 5432 is open on your system:
Which will output something like:
If this port is not on the list, use ufw to allow the port through the firewall:
If you’ve changed from the default PostgreSQL port in your configuration, you will need to adjust your firewall rule to match.
Checking PostgreSQL is Running on Red Hat, Fedora, Centos, etc
Like Ubuntu and Arch, you can use the systemctl command to check the status of the PostgreSQL service on Red Hat based distributions:
Checking the Firewall
The firewall-cmd command can be used to check that the default PostgreSQL port of 5432 is open on Red Hat based distributions:
postgressql and its port should be shown in the outputted list. If it is not, you can grant the PostgreSQL service network access through the firewall by running:
…or run the following to open the port:
Once changes have been made, apply them by reloading the firewall rules:
Other Linux Distributions
Most modern Linux distributions (based on systemd) will use the same systemctl syntax as above to check whether a service is running.
Checking the Firewall
In the unlikely scenario where you do not have access to ufw or firewall-cmd, you can write your own iptables rules to allow traffic through your systems firewall.
To continue your PostgreSQL journey, head back to our index that lists our full PostgreSQL guide.
Как проверить статус postgresql в linux
PostgreSQL is one of the frequently used relational databases that assist us in storing data securely and efficiently. It offers numerous features, such as security, faster query execution, open-source development, etc. However, you need to install Postgres on your machine to earn these features. The Postgres Service status needs to be checked after installation in order to use the PostgreSQL database smoothly.
This write-up will explain how to check the status of the Postgres service using practical demonstration. The outcomes of this post are enlisted below:
— How to Check if Postgres is Installed or Not?
— How to Check the Status of Postgres Service?
— How to Check if the Postgres Service is Active?
— How to Check if the Postgres Service is Enabled?
— How to Check if PostgreSQL is Ready to Accept/Recieve User Connections?
How to Check if Postgres is Installed or Not?
Firstly, launch the terminal and connect to the “postgres” user via the below-given “sudo” command:
Now run the “psql” command from the terminal to access the “postgres”:
The output proves that the Postgres database is installed on your Ubuntu system. If Postgres is not installed on your system then first, you must install it on your system.
How to Check the Status of Postgres Service?
Open the terminal and utilize the below-provided command to check the status of the Postgres service:
From the output snippet, you can observe that the “Postgres service” is currently enabled and active.
Alternatively, you can use the “systemctl” command with different options, like “is-active” or “is-enabled” to check the status of the Postgres service with respect to a specific parameter.
How to Check if the Postgres Service is Active?
Use the “systemctl” command with the “is-active” option to check if Postgres is operating or not:
The output shows that “Postgres” is active.
How to Check if the Postgres Service is Enabled?
Use the “sudo systmctl” command with the “is-enabled” option to check if the Postgres service is enabled or not:
The output proved that Postgres is currently enabled.
How to Check if PostgreSQL is Ready to Accept/Recieve User Connections?
Use the "sudo pg_isready" command to check whether Postgres is ready for client connections or not:
The output clarifies that Postgres is accepting the users’ connections at the default port, i.e., 5432.
That’s all from this guide.
Use the “sudo systemctl status postgresql” command to check the PostgreSQL service status in Linux. Users can also use the “sudo systemctl is-active postgresql” and “sudo systemctl is-enabled postgresql” commands to check if the Postgres service is active and enabled. Moreover, users can execute the "sudo pg_isready" command to check whether Postgres is ready for client connections or not.
This post presented a comprehensive guide on how to check the status of Postgres service on the Linux (Ubuntu) operating system.
Как проверить статус postgresql в linux
pg_ctl — initialize, start, stop, or control a PostgreSQL server
Synopsis
pg_ctl init[db] [ -D datadir ] [ -s ] [ -o initdb-options ]
pg_ctl start [ -D datadir ] [ -l filename ] [ -W ] [ -t seconds ] [ -s ] [ -o options ] [ -p path ] [ -c ]
pg_ctl stop [ -D datadir ] [ -m s[mart] | f[ast] | i[mmediate] ] [ -W ] [ -t seconds ] [ -s ]
pg_ctl restart [ -D datadir ] [ -m s[mart] | f[ast] | i[mmediate] ] [ -W ] [ -t seconds ] [ -s ] [ -o options ] [ -c ]
pg_ctl reload [ -D datadir ] [ -s ]
pg_ctl status [ -D datadir ]
pg_ctl promote [ -D datadir ] [ -W ] [ -t seconds ] [ -s ]
pg_ctl logrotate [ -D datadir ] [ -s ]
pg_ctl kill signal_name process_id
On Microsoft Windows, also:
pg_ctl register [ -D datadir ] [ -N servicename ] [ -U username ] [ -P password ] [ -S a[uto] | d[emand] ] [ -e source ] [ -W ] [ -t seconds ] [ -s ] [ -o options ]
pg_ctl unregister [ -N servicename ]
Description
pg_ctl is a utility for initializing a PostgreSQL database cluster, starting, stopping, or restarting the PostgreSQL database server ( postgres ), or displaying the status of a running server. Although the server can be started manually, pg_ctl encapsulates tasks such as redirecting log output and properly detaching from the terminal and process group. It also provides convenient options for controlled shutdown.
The init or initdb mode creates a new PostgreSQL database cluster, that is, a collection of databases that will be managed by a single server instance. This mode invokes the initdb command. See initdb for details.
start mode launches a new server. The server is started in the background, and its standard input is attached to /dev/null (or nul on Windows). On Unix-like systems, by default, the server’s standard output and standard error are sent to pg_ctl ‘s standard output (not standard error). The standard output of pg_ctl should then be redirected to a file or piped to another process such as a log rotating program like rotatelogs ; otherwise postgres will write its output to the controlling terminal (from the background) and will not leave the shell’s process group. On Windows, by default the server’s standard output and standard error are sent to the terminal. These default behaviors can be changed by using -l to append the server’s output to a log file. Use of either -l or output redirection is recommended.
stop mode shuts down the server that is running in the specified data directory. Three different shutdown methods can be selected with the -m option. “ Smart ” mode disallows new connections, then waits for all existing clients to disconnect. If the server is in hot standby, recovery and streaming replication will be terminated once all clients have disconnected. “ Fast ” mode (the default) does not wait for clients to disconnect. All active transactions are rolled back and clients are forcibly disconnected, then the server is shut down. “ Immediate ” mode will abort all server processes immediately, without a clean shutdown. This choice will lead to a crash-recovery cycle during the next server start.
restart mode effectively executes a stop followed by a start. This allows changing the postgres command-line options, or changing configuration-file options that cannot be changed without restarting the server. If relative paths were used on the command line during server start, restart might fail unless pg_ctl is executed in the same current directory as it was during server start.
reload mode simply sends the postgres server process a SIGHUP signal, causing it to reread its configuration files ( postgresql.conf , pg_hba.conf , etc.). This allows changing configuration-file options that do not require a full server restart to take effect.
promote mode commands the standby server that is running in the specified data directory to end standby mode and begin read-write operations.
logrotate mode rotates the server log file. For details on how to use this mode with external log rotation tools, see Section 25.3.
kill mode sends a signal to a specified process. This is primarily valuable on Microsoft Windows which does not have a built-in kill command. Use —help to see a list of supported signal names.
register mode registers the PostgreSQL server as a system service on Microsoft Windows . The -S option allows selection of service start type, either “ auto ” (start service automatically on system startup) or “ demand ” (start service on demand).
unregister mode unregisters a system service on Microsoft Windows . This undoes the effects of the register command.
Options
Attempt to allow server crashes to produce core files, on platforms where this is possible, by lifting any soft resource limit placed on core files. This is useful in debugging or diagnosing problems by allowing a stack trace to be obtained from a failed server process.
Specifies the file system location of the database configuration files. If this option is omitted, the environment variable PGDATA is used.
Append the server log output to filename . If the file does not exist, it is created. The umask is set to 077, so access to the log file is disallowed to other users by default.
Specifies the shutdown mode. mode can be smart , fast , or immediate , or the first letter of one of these three. If this option is omitted, fast is the default.
Specifies options to be passed directly to the postgres command. -o can be specified multiple times, with all the given options being passed through.
The options should usually be surrounded by single or double quotes to ensure that they are passed through as a group.
-o initdb-options
—options= initdb-options
Specifies options to be passed directly to the initdb command. -o can be specified multiple times, with all the given options being passed through.
The initdb-options should usually be surrounded by single or double quotes to ensure that they are passed through as a group.
Specifies the location of the postgres executable. By default the postgres executable is taken from the same directory as pg_ctl , or failing that, the hard-wired installation directory. It is not necessary to use this option unless you are doing something unusual and get errors that the postgres executable was not found.
In init mode, this option analogously specifies the location of the initdb executable.
Print only errors, no informational messages.
Specifies the maximum number of seconds to wait when waiting for an operation to complete (see option -w ). Defaults to the value of the PGCTLTIMEOUT environment variable or, if not set, to 60 seconds.
Print the pg_ctl version and exit.
Wait for the operation to complete. This is supported for the modes start , stop , restart , promote , and register , and is the default for those modes.
If the operation does not complete within the timeout (see option -t ), then pg_ctl exits with a nonzero exit status. But note that the operation might continue in the background and eventually succeed.
Do not wait for the operation to complete. This is the opposite of the option -w .
If waiting is disabled, the requested action is triggered, but there is no feedback about its success. In that case, the server log file or an external monitoring system would have to be used to check the progress and success of the operation.
In prior releases of PostgreSQL, this was the default except for the stop mode.
Show help about pg_ctl command line arguments, and exit.
If an option is specified that is valid, but not relevant to the selected operating mode, pg_ctl ignores it.
Options for Windows
Name of the event source for pg_ctl to use for logging to the event log when running as a Windows service. The default is PostgreSQL . Note that this only controls messages sent from pg_ctl itself; once started, the server will use the event source specified by its event_source parameter. Should the server fail very early in startup, before that parameter has been set, it might also log using the default event source name PostgreSQL .
Name of the system service to register. This name will be used as both the service name and the display name. The default is PostgreSQL .
Password for the user to run the service as.
Start type of the system service. start-type can be auto , or demand , or the first letter of one of these two. If this option is omitted, auto is the default.
User name for the user to run the service as. For domain users, use the format DOMAIN\username .
Environment
Default limit on the number of seconds to wait when waiting for startup or shutdown to complete. If not set, the default is 60 seconds.
Default data directory location.
Most pg_ctl modes require knowing the data directory location; therefore, the -D option is required unless PGDATA is set.
pg_ctl , like most other PostgreSQL utilities, also uses the environment variables supported by libpq (see Section 34.15).
For additional variables that affect the server, see postgres .
Files
pg_ctl examines this file in the data directory to determine whether the server is currently running.
If this file exists in the data directory, pg_ctl (in restart mode) will pass the contents of the file as options to postgres , unless overridden by the -o option. The contents of this file are also displayed in status mode.
Examples
Starting the Server
To start the server, waiting until the server is accepting connections:
To start the server using port 5433, and running without fsync , use:
Stopping the Server
To stop the server, use:
The -m option allows control over how the server shuts down:
Restarting the Server
Restarting the server is almost equivalent to stopping the server and starting it again, except that by default, pg_ctl saves and reuses the command line options that were passed to the previously-running instance. To restart the server using the same options as before, use:
But if -o is specified, that replaces any previous options. To restart using port 5433, disabling fsync upon restart:
Showing the Server Status
Here is sample status output from pg_ctl :
The second line is the command that would be invoked in restart mode.
See Also
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