Add Linux and PostgreSQL commands

src/linux.md

@@ -1,4 +1,5 @@
 # Linux
+Specifically using Ubuntu.
 
 ## SSH
 Type `exit` to exit out of a SSH session.
@@ -24,6 +25,12 @@ sudo shutdown -r 5
 
 # Shutdown
 sudo poweroff
+
+# Get machine and kernel information.
+uname -mrs
+
+# Get distribution-specific information.
+lsb_release -a
 ```
 
 ### Updates
@@ -91,8 +98,10 @@ rm file.txt
 # Remove/delete an empty directory.
 rmdir path/to/directory
 
-# Remove/delete a directory, even if it has files.
+# Remove/delete a directory, even if it has files. (Only macOS?)
 rmdir -r path/to/directory
+# Works on Ubuntu.
+rm -r path/to/directory
 ```
 
 ### File viewing and creation
@@ -174,6 +183,12 @@ passwd <user>
 
 # List user information, including groups.
 id <user>
+
+# List all users.
+cat /etc/passwd
+
+# List all users across multiple sources.
+getent passwd
 ```
 
 ## Permissions

src/postgresql.md

@@ -2,10 +2,21 @@
 Unless otherwise noted, non-SQL commands are running under Ubuntu.
 
 ```bash
+# On Ubuntu, run psql as default postgres user.
+sudo -u postgres psql
+
 # List all databases.
 sudo -u postgres psql -l
 ```
 
+```sql
+-- List all databases.
+\l
+
+-- Quit psql.
+\q
+```
+
 ## Configuration
 
 ```bash
@@ -26,3 +37,27 @@ SHOW hba_file;
 -- Or just query the file for rules.
 select * from pg_hba_file_rules();
 ```
+
+## User management
+```sql
+-- List all users.
+\du
+
+-- Create a new user.
+CREATE USER <name>;
+```
+
+## Database management
+```bash
+# Create a new database.
+sudo -u postgres createdb <name>
+# Verify it was created.
+sudo -u postgres psql -l
+
+# Create a new database, echoing out the commands run.
+sudo -u postgres createdb <name> -e
+
+# Drop a database.
+sudo -u postgres dropdb <name>
+
+```