5.1.5. Other commands of operating system

Commands that follow do not belong to the group that is used during the operation, but used sporadically in specific situations, or give insight into the situation that almost never changes. Therefore, as described on a separate page. But it should be borne in mind that the available commands are listed in the content directories [/bin], [/sbin] and [/usr/bin], and can also be subsequently installed 'packages' of additional commands (utilities), the person commands, e.g. ' screen ' command to control which screens multiplex physical terminal between several processes, or specific program support ' mc ' (GNU Midnight Commander), which is nothing more than a very good handler files from TUI interface. Services provided by the server may have, as an electronic mail (MAIL), WWW services, LDAP and RADIUS services and similar subsequently installed, and often have their own commands for handling them. In further support includes such package 'samba' which allows access by installing the Windows users in their corresponding directories without FTP support. Maybe at the present time for this purpose better use NAS. To work remotely SSH uses the client software. Additional commands and has a lot of packages, and can be viewed on any of the Debian servers, such as the CARNet (ftp://ftp.carnet.hr//debian/pool/main).

Shutdown and restart

Turning your computer on and off is the responsibility of system administration, and only physical power is something that every user knows. But it is not good that the server of an institution or a company everyone can turn on and off at the discretion. Therefore, servers must be in a separate room in which only the administrator has access. The stability of the server is mandatory that each of them to the power supply (110/220 V AC) is connected via UPS. UPS.

shutdown - The procedure for switching off the computer, whereby the process stream does stop the service, storing of critical parameters and related security operations to the physical off. Previous exclusion can send messages to users that will be made after the expiry of specified time upon receipt of a message. However, as almost none of the users today serves no terminal-emulator warning message will not even see it, so the command ' shutdown -t 0 -h now ' to shut down computer without delay entirely acceptable. Servers should never force inextinguishable power cut as it may cause damage to the file system.
halt - Fast switching off the computer without any retention and warning messages. Of course, it is not excluded from the current!
poweroff - Symbolic link on the ' halt ' command, with the transfer of command names that indicates that the computer server to be physically shut down.
reboot - Symbolic link on the ' halt ', command to transfer calls to indicate that the computer-server needs to smother level BIOS and ga restart immediately.

Working in the background and specific commands

Refer to the unusual and non-everyday tasks.

bg - If the shell performs a job and want to start another job in the same screen without stopping first job, the first job can be put to work in the 'background', with command <CTRL> + <Z>. You may then run the second command, the second job. The first job will continue to run in the background until you need to send something to the screen, then it will stop and wait.
fg - Restoring the first job from the background to the 'foreground' regarding extensions work with him.
sftp - Encrypted FTP protocol. It will be used with an application on another computer for setting up personal web pages, or web site facility, or just to transfer files and their installation on the server for easy downloading from another location.
wget - Program to download files from the Internet with exactly known location - the URL (https://www.domain.type /directory_1/.. ../directory_N/file_name) and save it to the place from where the command is activated. If you use option ' -r ' and specify only the target directory it will download all the files and subdirectories in it, which can be read by default rights. Once the domain type must be considered to be below do not replace case sensitive.

Special characters in commands

When the command is entered, certain characters have special meaning to the shell before it starts interpreting commands. A much more detailed description can be obtained from the literature dealing with the shell, but you have to understand what is happening, or will get unexpected results. One thing is certain, special characters should not be in the file specification, or command options..

\ - Escape therefrom and other peculiarities.
[ ] - Appends the appropriate forms for a single character.
* - Wildcard (joker) to replace any term or name in full for anything.
? - Similar to the previous but only one character in the term.
( ) - Content of the rounded brackets is executed in another bowl.
; - Used to separate commands written in the same line.
& - An order to execute commands in the background. Same as <CTRL> + <Z>, but part of the command line.
> - Routing process output to a file or enter another process. The peculiarity of the '2 > file_name', or logging error messages during the course of a process in a particular file.
>> - Adding new data to the end of an existing file.
< - Entering data into a file either by typing, from another file or some other way.
| - Sign for chaining. Output data commands to the left of the entrance to fit the character of the command to the right of the sign.
&& - These characters are placed between the two commands in the same line and give them the command behind these characters will not run if you successfully complete this operation with command in front of characters.
| | - These characters are placed between the two commands in the same line and give them to complete command behind signs if one fails to perform the command in front of characters.
# - A sign is placed at the beginning of the line that contains an arbitrary comment. If the line determines the same logo that does not mean that something behind him to make; and that continue to the end of comment lines.
`` - Content surrounded by these quotes is executed as a command to which output is used as part of the command.
"" - Content surrounded by double quotes is treated as an argument, except for the parts inside the content surrounded by ' `` '.
'' - Content is surrounded by single quotes are passed to the command without any interpretation.

Peculiarities

Under this subheading is thought to commands and actions that are occasionally used to focus some jobs or get information on the computer-server about checking the operation or by introducing an administrator from the basic properties of the new server.

If the user is a directory of frequently used, and access to it time consuming, it is well under that directory making symbolic link of directories that are commonly used, as is usually the starting point (home) directory. Debian uses a multitude of symbolic links, as shown in previous examples. Creating symbolic link in the desired directory is specified with the command ' ln ':

ln -s path_to_the_destination link_name           (basic syntax)
ln -s /var/www/joomla index.html                  (example)

drago@voda:~$
su -                (prompt for password with transfer of environment variables)
voda:~#             (working directory of the user 'root')
voda:~# cd /
voda:/#                  (root directory of the system)
voda:/# cd /var/www      (retrieval of directories where is the real link)
voda:/var/www#
voda:/var/www# ln -s /var/www/joomla index.html
voda:/var/www# ls -al
    :
lrwxrwxrwx  1 root root  16 2009-01-31 12:13 index.html -> /var/www/joomla

In the above example, all calls to the file 'index.html' directed to a directory that is added to the file specified.

If you want to read the basic information about the server, or check if there are any changes when upgrading can serve the next set of commands:

Insight into the ID of system - a numerical identifier for a computer:
```
 drago@voda:/usr/bin$ hostid
 007f0101
 drago@voda:/usr/bin$
```

Insight into the computer name:

 drago@voda:/etc$ cat hostname 
 voda
 drago@voda:/etc$

Family of operating system:

 drago@voda:/etc$ cat issue
 Debian GNU/Linux 5.0 \n \l

 drago@voda:/etc$

Insight into the operating system version:

 drago@voda:/etc$ cat debian_version 
 5.0.5
 drago@voda:/etc$

Insight into network interface cards (NIC) and the IP parameters:

 drago@voda:~$ ip addr
 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
     inet 127.0.0.1/8 scope host lo
     inet6 :1/128 scope host 
        valid_lft forever preferred_lft forever
 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN
     link/ether 00:03:ff:66:10:46 brd ff:ff:ff:ff:ff:ff
     inet 192.168.0.11/24 brd 192.168.0.255 scope global eth0
     inet6 fe80:203:ffff:fe66:1046/64 scope link 
        valid_lft forever preferred_lft forever
 drago@voda:~$

To work network card it is important to state that ' eth0 ' and that there is ' UP ' - works!

Following command can be executed only SUPERVISOR, and gives a complete insight into the parameters of network communication.

 voda:~# ifconfig
 eth0      Link encap:Ethernet  HWaddr 00:03:ff:66:10:46
           inet addr:192.168.0.11  Bcast:192.168.0.255  Mask:255.255.255.0
           inet6 addr: fe80:203:ffff:fe66:1046/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:45861 errors:0 dropped:0 overruns:0 frame:0
           TX packets:22407 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:68315340 (65.1 MiB)  TX bytes:1564665 (1.4 MiB)
           Interrupt:11 Base address:0xec00

 lo        Link encap:Local Loopback
           inet addr:127.0.0.1  Mask:255.0.0.0
           inet6 addr::1/128 Scope:Host
           UP LOOPBACK RUNNING  MTU:16436  Metric:1
           RX packets:26 errors:0 dropped:0 overruns:0 frame:0
           TX packets:26 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:2762 (2.6 KiB)  TX bytes:2762 (2.6 KiB)
 voda:~#

To check the network communications used commands ' ping ' and ' tracert ' with use as the Windows operating system, as described in the Chapter 7.4.4, except that the first command can execute each user and the second command only superuser (root).