Command of the week #3

This week’s command is: useradd.

This command is used to add new users to your linux system. The syntax is as follows:
useradd [options] [user]

The following was taken from a great site for learning about linux commands( and will further explain the command:

-c comment Comment field.

-d dir Home directory.
The default is to use user as the directory name
under the home directory specified with the -D option.

-e date Account expiration date.
date is in the format MM/DD/YYYY.
Two-digit year fields are also accepted.
The value is stored as the number of days since January 1, 1970.
This option requires the use of shadow passwords.

-f days Permanently disable account this many days after the
password has expired. A value of -1 disables this feature.
This option requires the use of shadow passwords.

-g group Initial group name or ID number.
If a different default group has not been specified using the -D option,
the default group is 1.
-G groups Supplementary groups given by name or number in a comma-separated
list with no whitespace.

-k [dir] Copy default files to user’s home directory.
Meaningful only when used with the -m option.
Default files are copied from /etc/skel/ unless an alternate dir is specified.

-m Make user’s home directory if it does not exist.
The default is not to make the home directory.

-o Override. Accept a nonunique uid with the -u option. (Probably a bad idea.)

-s shell Login shell.

-u uid Numerical user ID. The value must be unique unless the -o option is used.
The default value is the smallest ID value greater than 99 and greater
than every other uid.

-D [options] Set or display defaults. If options are specified, set them.
If no options are specified, display current defaults. The options are:

-b dir Home directory prefix to be used in creating home directories.
If the -d option is not used when creating an account, the
user name will be appended to dir.

-e date Expire date. Requires the use of shadow passwords.

-f days Number of days after a password expires to disable an account.
Requires the use of shadow passwords.

-g group Initial group name or ID number.

-s shell Default login shell.

Command of the week #2

This week’s command is: alias

This command is great. In short it allows you to create Pseudo commands.

For example, on the server that this site runs on (my server), I regularly need to check to see what connections my computer has initiated, and what services they’re through. I do this using the linux command netstat using the following command line string: “netstat -pan | grep tcp“. Since I’m not doing this blog on netstat I will not explain that to you. If you have any questions, just comment on this post below and either me(Jon) or Kyle will attempt to explain it to you.

Now isn’t that command a little bit cumbersome? I think so at least. This is where alias comes in handy.

To set up an alias in your *nix based profile do the following things:

  1. Login as your user
  2. Type in cd ~
  3. Edit your .bashrc file using the text editor of your choice. I’ll be using vi, so I’ll type in vi .bashrc
  4. You create an alias using the following syntax: alias NEW_COMMAND=”COMMAND STRING_TO BE EXECUTED”
  5. Using the example above you would type in the following: alias ns=”netstat -pan | grep tcp”

So now anytime that you enter “ns”, “netstat -pan | grep tcp” will be executed in it’s place.

I should mention that you don’t have to place the alias command in your .bashrc file. You can also run it on the commnad line, but it will only have its effect for the current session.

Hopefully this’ll help you out at some point.

More later,
Jon Howe

Command of the week #1.5

Alright, I told you that I’d be posting another quickie on screen so here it is.

There’s not much more to talk about that’s relevant, except for one piece.

Restoring from saved sessions:
In order to view the saved sessions enter screen -r. you should be presented with a list of available sessions.
To restore a session enter the following command: screen -r SESSION_NAME.

That’s pretty much all that you need to know.

More tomorrow,
Jon Howe