Extremely Serious
| Command | Description |
|---|---|
| postqueue -p | Display the queue |
| postcat -vq <QUEUE_ID> | View the content of the email |
| postsuper -d ALL | Remove all emails |
| postsuper -d <QUEUE_ID> | Remove a particular email |
| postqueue -i <QUEUE_ID> | Attempt to send one particular email |
| Token | Description |
| QUEUE_ID | Can be identified by displaying the queue. |
Syntax
To sync some of your local directories to another local directory, you can use the following syntax:
rsync -av -L --delete <DIR1>[[ <DIR2>] <DIRn>] <DESTINATION_DIR>
| Token | Description |
| DIR1, DIR2, DIRn | These are the local directories you've wanted to be synced. Only DIR1 is required and the rest are optional. |
| DESTINATION_DIR | The destination directory on the remote machine. |
Example
rsync -av -L --delete /var/log/ /data/log/
| Variable | Description | Possible Values |
|---|---|---|
| GIT_CURL_VERBOSE | Tells Git to emit all the messages generated by that library. This is similar to doing curl -v on the command line. | 1 |
| GIT_SSL_NO_VERIFY | Tells Git not to verify SSL certificates. | true |
| GIT_TRACE | Controls general traces | 1, 2 or true |
| GIT_TRACE_PACKET | Enables packet-level tracing for network operations. | true |
ssh-keygen -t ed25519
ssh-copy-id -i ~/.ssh/id_ed25519.pub <USER>@<HOST>
| Token | Description |
| USER | A valid user on the host computer. |
| HOST | The host that has an active ssh service. |
If ssh-copy-id command doesn't work, you can directly append the content of the id_ed25519.pub file to the ~/.ssh/authorized_keys file (i.e. create this file if it doesn't exists) of the target <USER> on the target <HOST>.
Create a new alias for postfix service by updating the following file:
/etc/aliases
Each entry in the file must have the following syntax:
<ALIAS>: <USER1>[[, <USER2>], <USERn>]
| Token | Description |
| ALIAS | The desired email alias. |
| USER1, USER2, USERn | USER1 is required and the rest are optional. Each user must be delimited by a comma.
The target user of the alias must be a valid user of the system with a home directory. |
Example:
postmaster: root
After updating the file, you must execute the following command:
sudo newaliases
compile group: 'org.apache.derby', name: 'derby', version: '10.15.1.3' compile group: 'org.apache.derby', name: 'derbyshared', version: '10.15.1.3'
requires org.apache.derby.engine; requires org.apache.derby.commons; requires java.sql;
final String DATABASE_NAME = "sample_table";
String connectionURL = String.format("jdbc:derby:%s;create=true", DATABASE_NAME);
connection = DriverManager.getConnection(connectionURL);
connection.close();
boolean gotSQLExc = false;
try {
//shutdown all databases and the Derby engine
DriverManager.getConnection("jdbc:derby:;shutdown=true");
} catch (SQLException se) {
if ( se.getSQLState().equals("XJ015") ) {
gotSQLExc = true;
}
}
if (!gotSQLExc) {
System.out.println("Database did not shut down normally");
}
A clean shutdown always throws SQL exception XJ015, which can be ignored.
Values can become a valid record source for select statement if the values has table alias and column names as follows:
SELECT dummy_table.*
FROM (VALUES ('record1'),
('record2'),
('record3'),
('record4'),
('record5'),
('record6'),
('record7'),
('record8'),
('record9')) dummy_table (column1)
From the preceding select statement, the dummy_table is the table alias and the column name is column1.
Use the following command to create a detached ASCII signature:
gpg --armor --output <ASC_FILE> --detach-sig <FILE_TO_SIGN>
Run the following command:
gpg --receive-keys <KEY_ID>
Run the following command:
gpg --fingerprint <KEY_ID>
gpg --verify <ASC_FILE> <SIGNED_FILE>
gpg --full-gen-key
Please select what kind of key you want: (1) RSA and RSA (default) (2) DSA and Elgamal (3) DSA (sign only) (4) RSA (sign only) Your selection?
RSA keys may be between 1024 and 4096 bits long. What keysize do you want? (2048)
Please specify how long the key should be valid.
0 = key does not expire
<n> = key expires in n days
<n>w = key expires in n weeks
<n>m = key expires in n months
<n>y = key expires in n years
Key is valid for? (0)
Key does not expire at all Is this correct? (y/N)
Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit?
The output will be ending with something like the following:
pub rsa2048 2019-11-27 [SC]
8C99E30527B112D1CB6D646FE86A4FE7189AADC9
uid Real Name <real_email@email.com>
sub rsa2048 2019-11-27 [E]
The second line is the PGP key ID. Thus from the output above. The key id is:
8C99E30527B112D1CB6D646FE86A4FE7189AADC9
The my-secret-key.pgp file generated by this command can be use for signing your binaries.
Run the following command:
gpg --export-secret-keys <KEY_ID> > my-secret-key.pgp
DO NOT SHARE THIS FILE OR COMMIT TO YOUR REPOSITORY.
Run the following command:
gpg --keyserver hkp://keys.openpgp.org --send-keys <KEY_ID>
This will only work if you submit your keys using the preceding section.
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