Linux how to select all

Steven-Rose / gist:3943830

Select all and delete (actually move to buffer )

: % d

Select all and copy to buffer

: % y

Use p to paste the buffer .

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deven003 commented Mar 19, 2016

Thanks, it worked.

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0x008800 commented Dec 29, 2017

Very useful! Thank!

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Linux List All Users In The System Command

Table of contents

Linux list all users account using the /etc/passwd file

In order to list all users on Linux, use the cat command as follows:
$ cat /etc/passwd
Here is what I see:

Each line in the file has seven fields as follows. For example, consider the following line:
vnstat:x:131:137:vnstat daemon. /var/lib/vnstat:/usr/sbin/nologin
Where,

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• vnstat – The user name or login name.
• x – Encrypted password is stored in the /etc/shadow file.
• 131 – UID (user ID number)
• 137 – Primary GID (group ID number)
• vnstat daemon – GECOS. It may includes user’s full name (or application name, if the account is for a program), building and room number or contact person, office telephone number, home telephone number and any other contact information.
• /var/lib/vnstat – Home directory for the user.
• /usr/sbin/nologin – Login shell for the user. Pathnames of valid login shells comes from the /etc/shells file.

How to list users in Linux using pagers

Of course we can use pagers such as more/less commands as follows to view the /etc/passwd file:
$ more /etc/passwd
$ less /etc/passwd
Sample outputs:

Fig.01: List users using /etc/passwd

Linux list user names only

To list only usernames type the following awk command:
$ awk -F’:’ ‘< print $1>‘ /etc/passwd
Sample outputs:

Another option is to use the cut command:
$ cut -d: -f1 /etc/passwd

Get a list of all users using the getent command

To get a list of all Linux users you can type the following getent command:
$ getent passwd
$ getent passwd | grep tom
## get a list all users ##
$ getent passwd | cut -d: -f1
## count all user accounts using the wc ##
$ getent passwd | wc -l
One can use the compgen command on Linux to list users and other resources too:
$ compgen -u

Find out whether a user account exists in the Linux server

We can use above commands to see whether a user exists in the Linux machine as follows using the grep command:

A simplified command would be:

How to count user accounts in the Linux server

Want to get user accounts count on your system? Try the wc command as follows:
$ compgen -u | wc -l
$ getent passwd | wc -l

A Note About System and General Users

Each user has numerical user ID called UID. It is defined in /etc/passwd file. The UID for each user is automatically selected using /etc/login.defs file when you use useradd command. To see current value, enter:
$ grep «^UID_MIN» /etc/login.defs
$ grep UID_MIN /etc/login.defs
Sample outputs:

1000 is minimum values for automatic uid selection in useradd command. In other words all normal system users must have UID >= 1000 and only those users are allowed to login into system if shell is bash/csh/tcsh/ksh etc as defined /etc/shells file. Type the following command to list all login users:

To see maximum values for automatic uid selection in the useradd command, enter:
$ grep «^UID_MAX» /etc/login.defs
Sample outputs:

In other words, all normal system users must have UID >= 1000 (MIN) and UID /etc/shells file. Here is an updated code to get details:

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6 Different Ways to List Hard Drives in Linux

There are several ways to list all the hard drives present in a system through Linux command lines.

Keep in mind a hard drive could be physically connected, virtually connected or even emulated (for example: when you use storage devices such as EMC, Sun or IBM).

Here are some different commands which can list the hard drives, keep in mind there are others but these are probably the most commonly used and easy to get the job done.

Listing Hard Drives in Linux

Please note that some of these commands are actually disk partitioning tools and listing disk partition is one of their features.

Let’s see what commands you can use to show disk info in Linux.

The df command in Linux is probably one of the most commonly used. It lists the actual “disk space usage” and it can give you information about what hard disks (or current disk space) is being used in the entire system.

The most common way to use it is with the -h argument which means “human readable” (because we are not machines, right?):

As you can see, the first column is the current logic name (or the name you can find it within your system), the second column is how big is each of them, the third column is how much is currently used (in bytes), the fourth column is how much is currently available in each for usage (in bytes), the fifth column is how much is used (in %) and the sixth and last column is where is it physically mounted in your Linux system.

2. fdisk

fdisk is another common option among sysops. It currently lists the different partitions (which is related to hard drives as a hard drive can be divided into several partitions) in your system.

This will return the entire amount of space (in GB or MB), the entire amount of bytes and the entire amount of sectors per each partition and as a summary, it also gives you the start and end sectors, the amount of disk space (in Bytes) and the type of partition.

Tip: Usually a SATA disk is labelled with sd.

3. lsblk

This one is a little more sophisticated but gets the job done as it lists all block devices. It will give you a very simple list of all devices:

It is probably more visual than the others as it even shows the partitions per each disk in a visual way (like the sda in the example above). It also gives information about the total size per each partition and disk and the physical location for each. This is very commonly used when you need to mount things to be used (like a USB stick or similar) so you can know where is it in order to proceed to mount it.

4. cfdisk

cfdisk is probably the most advanced one in GUI (Graphical User Interface), as it is absolutely visual and interactive. It allows at first to list all disks/partitions in your system but it also allows you to manage them by selecting them and then applying actions such as “Delete”, “Resize”, “Type” (to change partition Type) and “Write” changes done to partitions.

cfdisk example

It also gives you very friendly information about each partition and disk as it gives you where does each partition cylinders start and ends, amount of sectors used by each one and the full size of each one with its type. It won’t give you for example how much is used or free to use.

5. parted

This one is similar to previous ones mentioned, it lists all partitions and allows to manage them. Its main difference is that it also informs you the brand and model of your hard disks and even the type of connectivity used in it (scsi, sata, etc) and total disk size.

6. sfdisk

This is very similar to fdisk, however sfdisk allows you to see both physical and logical volumes and also gives you a “summary” of the actual physical volumes’ partitions with the cylinders (start and end), sectors, size and type.

Probably the “s” is for “super”, as it is a fdisk with super powers:

These commands should allow you to at least see what logical volumes, partitions and hard drives you have in your system and make use of this information for whatever reason you need it, being this just to know more or manipulate any of these.

Most of these commands also give you managing capabilities to modify and manipulate partitions at your will, so make sure to use them with responsibility.

If you like checking system information, do read the article about getting processor information in Linux command line.

If you have any questions or suggestions, do let me know in the comment section.

Источник

How can I Select and Delete all Text in Nano?

For selecting and deleting all text in the nano editor, you first need to open a text file with this editor via the terminal with the following command:

You can replace Testing with the name of your particular text file. Running this command will open your specific text file with the nano editor.

Now point your cursor to the beginning of the file with the help of the arrow keys and then press Ctrl+ A to set the beginning marker. After pressing this key combination, you will be able to see the “Mark Set” indicator on your file as shown below:

Once the beginning mark has been set, make use of the right arrow key to select the entire text of the file. Once all the file content has been selected, it will appear as highlighted in white color as you can see from the following image:

Now when all the text has been selected, just press Ctrl+ K key combination to delete the selected text. After pressing this key combination, you will no longer be able to see the selected text in your file as shown in the image below:

In the same manner, you can even select and delete a specific portion of the text file by setting a marker at the beginning of that portion with Ctrl+ A shortcut combination, then heading to the end of the portion of your choice with the right arrow key, and then deleting that portion by pressing Ctrl+ K shortcut combination.

About the author

Karim Buzdar

Karim Buzdar holds a degree in telecommunication engineering and holds several sysadmin certifications. As an IT engineer and technical author, he writes for various web sites. He blogs at LinuxWays.

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Tutorial requirements
Requirements	Linux
Root privileges	No
Difficulty	Easy
Est. reading time	5 mintues