obtain free SMIME Certificates
Free certificates usable for S/MIME are available from:
Some of them are free only for personal use. It can also cost money to revoke a free certificate.
Let’s Encrypt does not currently offer S/MIME certificates. See https://community.letsencrypt.org/t/s-mime-certificates/153 for a thread explaining why you can’t use their SSL/TLS certificates for S/MIME.
To obtain certificate from an authority
Safari, Firefox and Microsoft Internet Explorer contain cryptotools capable of generating public/private keypairs. When signing up for a certificate with an authority, their website triggers your browser to create a keypair and transmit to them the public key, which is then certified. For this reason, when you return to pick up your completed certificate (typically a few minutes later), it is mandatory that you do so with the same browser on the same computer . You will otherwise not possess the private key necessary for pickup.
Be thoughtful about whether to select to “digitally sign all messages by default”. Institutional firewalls may protect their own security protocols and break your cryptographic signature, leaving your recipient with all kinds of warnings about the message being invalidly signed. As S/MIME usage is still not widespread, most people still don’t know how to interpret this. A broken signature will probably seem worse to them than receiving a message with no crypto signature at all, even though the contents are identical in both cases.
Webmail users will see an unreadable attachment which can raise similar questions.
Uncomment baseurl in this file: /etc/yum.repos.d/CentOS-Base.repo
In this block:
name=CentOS-$releasever - Base
By uncomment, I mean change this:
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/, to this:
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/ (remove the #).
Upgrading from previous versions of OS X
Upgrading from OS X Snow Leopard or Lion
If you’re running Snow Leopard (10.6.8) or Lion (10.7) and your Mac supports macOS High Sierra, you will need to upgrade to El Capitan first. Click here for instructions: https://support.apple.com/en-us/HT206886
Upgrading from OS X Leopard
If you’re running Leopard and would like to upgrade to macOS High Sierra, first you’ll need to upgrade to OS X Snow Leopard. You can purchase OS X Snow Leopard from the Apple Online Store.
Launch Terminal if you haven’t done so yet (/Applications/Utilities/) and issue the following command to turn off Gatekeeper:
sudo spctl --master-disable
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find /path/to/files -iname .DS_Store -delete
FreeBSD Display todays date
Type date command as follows, to display todays date and time:
Thu Feb 9 23:43:19 IST 2006
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Enter OS X Recovery Mode
To boot into OS X Recovery, the first thing you need to do is to restart your Mac. While restarting, hold down CMD + R until the Apple logo appears. If you time it right, you will enter the recovery mode.
What you need to do next is to go to Utilities > Terminal to open a Terminal. In Terminal, type
resetpassword and press Enter.
You will now be presented with the Reset Password window. Next, select your OS X drive. From the drop-down under “Select the user account:”, choose the user account that you want to reset password for.
Type in your new password, re-enter it and try not to forget it this time. You can also choose to write down a hint in the “Enter a new password hint for this user (optional)”, just in case.
Once you’re done, click on Save. You will be prompted with this message saying that your user account password was reset but your keychain is not. Just click OK and close all windows.
Now click the Apple icon at the very top left and choose Restart. You can now enter your account with your new password.