A factory reset, also known as master reset, is a software restore of an electronic device to its original system state by erasing all of the information stored on the device in an attempt to restore the device to its original manufacturer settings. Doing so will effectively erase all of the data, settings, and applications that were previously on the device. This is often done to fix an issue with a device, but it could also be done to restore the device to its original settings.[1] Such electronic devices include smartphones.
This will properly scale the game with your desired resolution across 21:9 or multiple monitors.
Since a factory reset entails deleting all information stored in the device, it is essentially the same concept as reformatting[1] a hard drive. Pre-installed applications and data on the card's storage card (such as a microSD card) will not be erased. A factory reset effectively destroys all data stored in the unit.
Factory resets can fix many chronic performance issues (i.e. freezing), but it does not remove the device's operating system.[2]
Examples[edit]
Factory resets can be achieved in a variety of ways depending on the electronic device. For some devices, this could be done by going into the device's Service Menu. Other devices may require a complete re-installation of the software. The following section lists a few common electronic devices and how they can be reset to factory settings.
Computer factory resets will restore the computer to the computer's original operating system and delete all of the user data stored on the computer. Microsoft's Windows 8 and Windows 10, and Apple's macOS have options for this.
On Android devices, there is a factory data reset option in Settings that will appear to erase all of the device's data and reset all of its settings. This method is typically used when the device has a technical problem that cannot be fixed using other methods, or when the owner wants to remove all their personal data before selling, giving away, returning or disposing of the device. After performing a study, Avast! reported that the data is recoverable using forensics software that is fairly generic and publicly available.[3] The 'Factory data reset' option does not affect the Knox Flag. As such, it does not reset the device to its original factory settings and is not a way to return the device to a state compatible with the manufacturer's warranty. Data on the SIM card and the microSD card is not erased.
Many other devices can be restored to factory settings, like televisions, GPS units or tablet computers.
Many electronic devices have a menu with tools and settings called the service menu,[4] which commonly includes a tool that performs a factory reset. This tool is most common in devices with displays, such as television sets and computer monitors. These menus are usually accessed through a sequence of button presses.
^'Guide for Performing Factory Resets on Common Mobile Devices'(PDF). Archived from the original(PDF) on 13 November 2013. Retrieved 23 October 2013.
^Jaromír Hořejší (9 July 2014). 'Android Forensics, Part 1: How we recovered (supposedly) erased data'.
^'Service Menu Instructions'(MediaWiki).
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Factory_reset&oldid=937326237'
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Postfix is a Secure Mail Transfer Agent.
Contents
Postfix
Postfix and mailing lists
Postfix and TLS/SSL
Advanced options
Installing and Configuring Postfix on Debian
Install postfix (this will remove exim since there can't be two mail systems). (If you have a website, choose 'Internet Site' if the configuration prompts ask for it.):
Check the log mail.log, mail.err, mail.info, mail.warn to see if postfix runs.
Add your domain to the config files, so others can't abuse your mailsystem:
Add your hostname (computer name). (Use command 'hostname' at the command-line to display your hostname if not sure.)
Now add the domain names that your system will handle.
Reload Postfix Server:
Test the mailserver. Type
You should see:
Send an email to yourself:
To end data hit enter, type in a dot, and hit enter again:
Then
You're done. Type 'mail' in the command-line terminal and see if you have some.
Now let's go to the next step:
If you have a router with firewall, enable port 25 and forward that port to your computer.
Enter your MX records in your domain provider. (e.g. godaddy.com or dnspark.com)
Check your mx records: go to http://www.iptools.biz/ locate 'DNS lookup'. From pulldown menu select 'MX'. Type in your domain name (ex. example.com). You should see some records there. If you don't see any MX records go back to previous step. You have to have MX record otherwise other computers won't be able to see you when sending emails.
Useful commands:
You should be set. If your isp is blocking the traffic then you might need to login to their smtp services. See Postfix and sbcglobal/yahoo/att below.
anti-spam: smtp restrictions
The first fight starts at your server so this should be added to any email server that you setup. This makes sure that any computer that tries to send an email to you has a valid domain name. (spammers use ex. myhomepc as a domain name. This will stop them from spamming you.)
Insert this in your /etc/postfix/main.cf:
anti-spam: Using RBL Lists
RBL list is a list of domains which says whether they are spammers or not.
Insert this in your /etc/postfix/main.cf:
See what rbl is about: http://www.us.sorbs.net/mailsystems/postfix.shtml for pre 2.3 and http://www.sorbs.net/mailsystems/postfix-2.3.shtml for 2.3 and later
and avoid such blacklists
Debian Anti-Spam Anti-Virus Gateway Email Server
If you are building anti spam system that will act as a gateway. Read below. If you want to add more anti-spam restrictions this is worth reading.
Debian Anti-Spam Anti-Virus Gateway Email Server
Forward Emails
Forwarding emails can be done via alias file located in /etc/aliases
Run this command to add alias maps:
You can now add your user to /etc/aliases like this:
You can forward your emails to a different email address
Or you could forward your email while still getting a copy in your local mailbox
When done adding aliases run this command which will create a database like file.
Reload postfix
Virtual Emails
If you want virtual emails such as abuse or postmaster you can do the following.
Run this command to add virtual alias maps:
Create a /etc/postfix/virtual file
And add your virtual emails
Create a database like file out of it
Reload postfix
Maildir
To use maildir format in your mailbox which creates separate files for each email you can use the following commands:
Maildir has few advantages over mbox format. (It keeps emails in separate files, allows for multiple applications to read mail, etc.)
Issue these commands:
You are done. Now your mail goes to Maildir format.
Mutt
If you want to read your new maildir format you have to tell mutt to use it as well. Edit this file:
Add these lines to the bottom of the file:
Now start mutt and send an email to yourself to see if it all works.
Mailman with Postfix
The instructions below are WRONG! You should not postfix-to-mailman.py and alias at the same time. Please read /etc/mailman/postfix-to-mailman.py instead.
Install mailman:
When done type:
Start mailman
You should be able to see mailman running now. Visit:
Because postfix is a secondary choice for Debian we need to add:
Edit /etc/postfix/main.cf; where you see 'relay_domains' add lists.yourdomain.com. You would get something like this:
In same file add ,hash:/var/lib/mailman/data/aliases after alias_maps
Now type:
In /etc/postfix/master.cf add:
Edit or create /etc/postfix/transport. Add this line:
Then postmap it:
Now edit /etc/mailman/mm_cfg.py and add:
Done. Now restart postfix, mailman
Create a mailing list:
If you want archives add this to /etc/apache2/apache2.conf
Then you need to reload apache:
Done. Go to
Mailman Troubleshooting
Connection refused
Assuming your postfix is running and listening on localhost, another possible problem is that postfix is not configured to run in IPv6 mode, but your /etc/hosts file specifies ::1 as localhost. In that case mailman tries to send mails to ::1 which has no postfix listening, thus resulting in a (111, 'connection refused') error.
Adding TLS/SSL
There are three options for transferring data to Postfix (smtpd):
Do not use TLS/SSL at all (only unsecure connections are available).
Use TLS/SSL, if possible. Fall back to unsecure connections otherwise.
Only allow TLS/SSL (unsecure connections are not available).
The second option (called STARTTLS) is recommended for general purpose mail servers. It provides some sort of 'compatibility mode'. Secure data transfer is enabled but not enforced.
STARTTLS connections start unencrypted via the regular smtp port 25. If both sides agree the rest of the data transfer is encrypted, still using port 25.
Pure TLS/SSL uses it own port, usually smtps (465). See below.
Recent Postfix versions employ the parameter smtpd_tls_security_level to control TLS encryption (valid values are none, may or encrypt).
Previously two parameters (smtpd_use_tls and smtpd_enforce_tls) were used. They can be unset. See also the Debian bug report 520936.
With the following commands TLS is enforced (no STARTTLS) and the old configuration parameters are reset to default values:
Alternate TLS/SSL Ports
You may be interested in supporting the smtps and/or submission ports (see /etc/services) so that your mobile/remote users who may be on a system that blocks, filters or poorly proxies SMTP (port 25) traffic can still send mail through your server. Since these ports are not also used for MTA to MTA traffic, you can enforce extra restrictions such as requiring SSL/TLS.
We do this by modifying the file /etc/postfix/master.cf to run additional smtpd services with special parameters on dedicated ports.
Submission
The submission port (587), covered in RFC 2476, is reserved for mail user agents (MUA)/ mail submission agents (MSA) to send email to a mail transfer agent (MTA).
In order to enable an additional service edit the file /etc/postfix/master.cf.
In this example we disallow ETRN, require TLS and enable SASL Auth on the submission port.
SMTPS
The smtps (or ssmtp) port (465) is the equivalent of https. The secure layer is expected from the get-go and not an optional negotiated parameter after connecting.
Whether the port is named smtps or ssmtp depends on the contents of your /etc/services file. On Debian both names seem to be defined. The output of netstat -tl shows ssmtp.
In order to enable an additional service edit the file /etc/postfix/master.cf.
On Debian there is already a prepared entry for smtps but commented out. Remove the '#' characters to enable it.
Connections from Fetchmail to Postfix
It seems fetchmail is not able to setup a TLS connection to Postfix. (Not to be confused with fetchmail's capabilities to fetch mails via TLS connections.)
If Postfix is configured to only accept TLS connections (smtpd_tls_security_level=encrypt) fetchmail will fail with an error like 'Must issue a STARTTLS command first'.
One way to escape from this is to provide an unencrypted smtp service. Of course, this service should be available for a local fetchmail process only.
Edit /etc/postfix/master.cf and add
This will add an additional smtp service listening on port 40025 with TLS disabled but only accepting local connections.
Fetchmail has to be configured accordingly via the option smtphost.
Edit /etc/fetchmailrc
The smtphost option is a so called 'user option'. It must be added to every user section.
Alternatively fetchmail can be instructed to use an external TLS-capable program1 to forward mails. This is not handled here. And if fetchmail and Postfix run on the same machine it does not make much sense anyway.
SPF and multiple external ip addresses
Explanation
I have some systems that are networked on an internal private ip address subnet (192.168.0.0/16). For a few reasons I email reports and such to <user>@mail.internal where user is an address that is not valid for receiving mail via the external interfaces. These systems also share a public ip address subnet so they could email each other that way, but I'd prefer they didn't for local addresses. I have published SPF records for the public mail servers because all of our mail routes through those servers so if others care to check they can ignore email claiming to be from us but being delivered from other servers as per our SPF record.
Recently I have expanded the ip addresses these systems are using externally to support multiple instances of port-based services like https (adding :oddport doesn't impress the customers.) I could have expanded or added more liberal SPF record values, or added more forward and reverse DNS records but I wanted to stick with less ip addresses.
So to recap my system has:
eth1 <public ip with spf published>
eth1:1 <public ip for extra port-based services>
eth0 <private ip on>
By using the settings in /etc/postfix/master.cf, /etc/postfix/main.cf and /etc/postfix/transport as outlined above I was able to get my outgoing smtp traffic to use my SPF published ip address once again.
Make SPF and multiple external ip addresses
If you are trying to implement SPF records while binding to one external ip address and still working with dual-homed multiple ip aliased systems, or have any other reason to support multi-homed systems with multiple ip addresses but want to limit postfix to use only two of them try this.
/etc/postfix/master.cf
clone the smtp (not smtpd) service. Set the first one to use <spf published ip address> Rename the second to smtpinternal and use <internal ip address>
/etc/postfix/main.cf
Use transport_maps for routing
/etc/postfix/transport
Map a transport for your internal domain.
Just postmap /etc/postfix/transport, invoke-rc.d postfix stop and invoke-rc.d postfix start and you should be in business. Email to <user>@<system>.internal will be delivered via the internal interface/ip address all other email will be delivered via default methods which means internet mail will go out the the spf published ip address.
Optional:
/etc/postfix/main.cf
Use the inet_interfaces setting to only listen on the ip addresses you want to.
Postfix and Sasl
SMTP server : SASL authentication in the Postfix SMTP server
SMTP client : SASL authentication in the Postfix SMTP client
Please see Postfix/Tutorials
Debian-specific information
postfix in the Debian package tracker
postfix bug in the Debian BTS
postfix manual pages in Debian
postfix in the Debian Security Bug Tracker
Upstream specific information
Homepage
Howtos and FAQs
Documentation
Other information
postfix on wikipedia
CategoryNetworkCategoryMailCategorySoftware
The so called 'lightweight' MTAs like msmtp or sSMTP. (1)