A veces en los bucles necesitamos saber si un número es múltiplo de otro. Con un sistema de paginar los resultados, y la solución es realmente fácil:
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$limite=20;
$numero=4;
for($i=0;$i<$limite;$i++){
if($i%$numero==0){
echo$i." es múltiplo de ".$numero;
}
}
La explicación es muy sencilla, si el valor de la variable que utilizamos para recorrer el múltiplo es $i, sólo debemos comprobar si ese valor, dividido entre el número del que queremos averiguar sus múltiplos tiene como resto 0. Para ello utilizamos : $i%$numero==0 Fuente: https://www.adaweb.es/numeros-multiplos-en-php/
By
default, WordPress requires a link when adding an item to your
website’s menu. But when you create a drop-down menu, you might not want
the parent item to be linked to any page – just the sub-menu items.
You can see this on my website as well. If you check out the Services menu item at the top, you’ll see that it’s not linking to any page.
So, how can you do that yourself? Very easily actually, and in this post, I’ll show you how!
Adding a menu item in WordPress without linking to a page
Step 1 – Log in to WordPress and go to Appearance -> Menus. Step 2 – Select the Custom Links section, add a Link Text (name of the menu item) and the # sign in the URL field. Step 3 – Press the Add to Menu button. Step 4 – Open the custom link that you added to the menu and remove the # sign. Step 5 – Add your sub-menu items and press the Save Menu button.
That’s it!
Now your WordPress menu item will not link to any page.
If you have installed the Postfix mail server to
operate as the Simple Mail Transfer Protocol (SMTP) service on an
email server, you might still need a way to retrieve the incoming mail
from the server.
This article shows you how to install and configure Dovecot, an
open-source Internet Message Access Protocol (IMAP) and Post Office Protocol
version 3 (POP3) server application designed specifically for Linux® and
UNIX® operating systems. Dovecot retrieves emails from Postfix and
delivers them to the relevant mailbox on the server.
You can get your mail through Dovecot by using either the POP3 or the IMAP
protocol.
Prerequisites
You need the following operating system and software to use Dovecot:
A CentOS® 6.0 or later Linux distribution
Postfix
Install Dovecot
Download and install the Dovecot package by running the following command:
$ sudo yum install dovecot
Configure Dovecot
After you install Dovecot, you need to configure the services in the
configuration file at /etc/dovecot/dovecot.conf. This example uses
the nano text editor, but you can use any text editor that you want.
Use the following command to open the file in nano:
$ sudo nano /etc/dovecot/dovecot.conf
Uncomment the following lines in the file and, if necessary, change them to
reflect your plans for the environment:
protocols: The protocols through which users can access their
email
mail_location: The format and the location of each user’s
mailbox
Configure the authentication process file
Next you need to configure the authentication process file,
which is located at /etc/dovecot/conf.d/10-auth.conf.
Use the following command to open the file in nano:
$ sudo nano /etc/dovecot/conf.d/10-auth.conf
Uncomment the following line in the file and, if necessary, change them to
reflect your plans for your environment:
auth_mechanisms = plain login
The auth_mechanisms parameter specifies the method that the email client
uses to authenticate with Dovecot.
Configure the mail location
You can set the location for your mail by editing the configuration file at
/etc/dovecot/conf.d/10-mail.conf.
Use the following command to open the file in nano:
sudo nano /etc/dovecot/conf.d/10-mail.conf
Either add or uncomment the following line in the configuration file:
mail_location = maildir:~/Maildir
Configure Postfix SMTP authentication
Next you need to configure the UNIX socket for Postfix SMTP
authentication (SMTP AUTH). The file that you need to change is located at
/etc/dovecot/conf.d/10-master.conf.
Use the following command to open the file in nano:
# Postfix smtp-auth
unix_listener /var/spool/postfix/private/auth {
mode = 0666
user = postfix
group = postfix
}
Configure POP3
Finally, configure the /etc/dovecot/conf.d/20-pop3.conf file, which enables
older and less popular email clients to connect and transmit messages
correctly.
Use the following command to open this file in nano:
The example in this section adds a mailbox that a hypothetical user named Joe
Bloggs (joe.bloggs) can use to send and receive emails.
You can create a user for this example, or you can use an existing user.
If necessary, use the following command to make a new user:
sudo useradd joe.bloggs
Use the following command to create the mail directory for your user:
sudo mkdir /home/joe.bloggs/Maildir
Give ownership of the mailbox that you just created to joe.bloggs by
changing its permissions:
After you have added the preceding lines, exit the main.cf file and
restart the Postfix service by using the following command:
sudo service postfix restart
Add ports to iptables
Now that you have enabled secure SMTP Secure Sockets Layer (SSL), you should
allow connections to port 587 by opening the port for your server in iptables.
Add the rule for this port by entering the following command:
Do you know “how to use USB memory
sticks with Linux”, If you are not sure then this article describes “how
to mount USB drive on a Linux system with command line interface”
Universal serial bus, or USB (also known
as Flash drive), is an electronic communications protocol that is
commonly used in computer accessories and other small devices. If you
have an up-to-date Linux system and a modern Desktop environment, your
device should show up on your desktop, with no need to open a
console. There are few important factors which are involved in learning
how to mount USB drive with Linux machine.
Following are the step by step instructions to understand further –
Step 1: Plug-in USB drive to your PC
Step 2 – Detecting USB Drive
After you plug in your USB device to your Linux system USB port, It
will add new block device into /dev/ directory. To verify it, use the
following command –
$ sudo fdisk -l
The sample output should be like this –
Disk /dev/sdb: 15.7 GB, 15664676864 bytes
255 heads, 63 sectors/track, 1904 cylinders, total 30595072 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/sdb1 * 32 30595071 15297520 c W95 FAT32 (LBA)
We can observe from the above result that, device boot, blocks, id and system format are displayed.
Step 3 – Creating Mount Point
To mount the USB, use the following command –
$ mount /dev/sdb1 /mnt
To create a directory in the mounted device, use the following commands –
$ cd /mnt
/mnt$ mkdir john
The above command creates a directory called john in USB device.
Step 4 – Delete a Directory in USB
To delete a directory in USB, use the following command –
/mnt$ rmdir john
Step 5 – Formatting the USB
You should unmount the device first to format the USB device, then use the following command to unmount the device –
$ sudo umount /dev/sdb1
Now use either of the commands as per file system based on your requirement. To format a USB drive, users generally prefer VFAT or NTFS file systems because they can be easily mounted on Windows operating systems and Linux systems.
Format vFat FileSystem
To format USB with vFat File System, use the following command –
$ sudo mkfs.vfat /dev/sdb1
Format NTFS FileSystem
To format a USB Flash Drive with NTFS file system, use the following command –
$ sudo mkfs.ntfs /dev/sdb1
Format EXT4 FileSystem
To format a USB with EXT4 file system, use the following command –
$ sudo mkfs.ext4 /dev/sdb1
Congratulations! Now, you know “How to Mount USB Drive in a Linux
System?”. We’ll learn more about these types of commands in our next
Linux post. Keep reading!
Everyone
has a flash drive. They’re great little things, and they make
safeguarding data easy. However, sometimes flash drives can get
corrupted or just flat out quit working. If you’re a Linux user and this
has happened to you, there’s an easy fix to all of this. In this
article we’ll go over a few really simple tricks on how you can get your
flash drive back in working order. Note: the tricks outlined in this article aren’t necessarily exclusive to USB drives and can be used on hard drives too.
Removing bad blocks from the USB drive with fsck
An easy way to repair a flash drive, or any drive really, is to use the fsck
tool. This tool is great for removing bad file blocks, as most (if not
all) corruption and unreadability comes from problems like this. To
remove the corrupted file blocks from the USB flash drive, open a
terminal window and enter the following commands.
Users must figure out what the drive designation is on the system before things can move forward. Do this by entering the lsblk command. This will list all of the attached disks on your system.
lsblk
Note: the lsblk
command lists all disks, not just USB drives. Pay close attention to
the output, as it is easy to mistake a hard drive for a flash drive.
To remove the bad file block, run the fsck
command on either a specific partition (e.g. /dev/sdc1), or the entire
disk (e.g. /dev/sdc). Once completed, the USB drive will have a healthy
partition again and be fully operational on Linux.
sudo fsck /dev/sdc1
Note:
this tutorial assumes that the flash drive is /dev/sdc (or /dev/sdc1).
Users may have different labels for their flash drive on their system.
Zeroing the USB drive
Sometimes
a USB drive can be totally unreadable to the point where it is no
longer worth saving. When this happens the best route is often to just
zero out the data and start over. The best tool for the job in this
situation is dd, and it works quite well.
Start by taking the drive label that was found earlier with the lsblk command, and apply the same logic (remember that /dev/sdc1 is a partition, and /dev/sdc is an entire device).
sudoddif=/dev/zero of=/dev/sdc
Making a new file system
Zeroing
a USB drive (or any device for that matter) renders the data on it
totally useless. This means that you’ll need to create a new data
partition. Choose a file system, and then run the command! Fat32
sudo mkfs.msdos -f 32 /dev/sdc1
Ext4
sudo mkfs.ext4 -f/dev/sdc1
NTFS
sudo mkfs.ntfs -f/dev/sdc1
Conclusion
USB
flash drives are useful devices. They make it easy for people to easily
transfer data from one computer to the other, regardless of the
operating system it’s running. That’s why it’s so important to know what
to do when the drive is no longer accessible. Luckily, Linux ships with
some really useful tools that make saving a flash drive quite easy.
Image credit: CES Thumb-Drive Style Press Kits
You just created a new page on your business’ WordPress site. You hit
Publish, and then check out finished page. In your address bar, you
notice something you didn’t expect. Instead of a clean URL, there’s a -2 at the end. For example, the URL is mysite.com/about-2/ instead of mysite.com/about/.
You try to edit the page, delete the -2 from the permalink, and click OK. But the -2 stays!
Now it seems you’re stuck with an unprofessional-looking URL on your
WordPress site. It’s not ideal. To get the permalinks you want for your
business, learn why the -2 happens, and how you can get rid of it.
The Cause
Every post, page, and media file in WordPress has a unique permalink.
When you create a new post, page or media file with the same name as a
previously existing item, WordPress will add a -2 to the end of the permalink (URL). It prevents duplication.
WordPress automatically generates permalinks based on the title of
the page, post, or media file. As a result, you might not be aware that
the URL you’re trying to use already exists until the -2 pops up in the permalink.
The Fix
This video walks through how to how to remove the -2 from a WordPress URL (permalink).
What if your permalink problem isn’t that simple? You can still fix it with these steps.
1. Find the Item
Make sure you’re logged into your WordPress account. Type the desired
permalink into your browser to see what’s there. If something loads,
you can click the Edit button in the Admin Toolbar at the top of the page and change it. If that doesn’t work, then you’ll have to do a little digging. Try the following in order:
Maybe the item isn’t published. Search through your site’s pages,
posts, and custom post types (such as portfolio items or testimonials).
To make this faster, use the search box on each of those pages in the
WordPress admin area.
Maybe a media item is using the permalink. Search through the Media Library.
Maybe the item is in the Trash. Go to the admin page for pages,
posts, and custom post types (such as portfolio items or testimonials).
Then click the Trash link at the top of the page. Search there. You can’t see the permalink of items in the Trash, so you’ll need to first Restore the item, then click the All link at the top of the page and look there.
What if you still can’t find the item? Search your database directly.
We recommend you do this only if you’re familiar with MySQL, because a
misstep could break your site. Here’s a tutorial on searching a MySQL database if you’re familiar with MySQL but need specific instructions.
2. Change the Permalink
Once you find the item that has the permalink you want to use, you need to permanently delete it or change its permalink. If you’ll never need the item again: Delete it by clicking Trash or Move to Trash. Typically this action frees up the permalink immediately. If it doesn’t, go to Trash and hit Permanently Delete. If you may need the item again: Edit the item, then edit the Permalink. Next click OK, and then Update.
There are a few extra steps to change the permalink of a media file. Edit the media item, click Screen Options at the top of the screen, and check the box for Slug. Scroll down to the Slug box at the bottom of the page and edit the slug. Click Update.
Once you’ve freed up your desired permalink, edit the item you want to have the permalink, and the Permalink. Click OK, and then Update (or Publish).
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