Tyler Chris - Fedora Linux стр 45.

$ nice -n15 xboard

To raise the priority of a process, you must be root ; supply a negative priority adjustment between 1 (slight boost in priority over normal) to 20 (highest priority):

# nice -n-12 xboard

4.9.3.3. ...changing the priority of an existing process?

$ xboard &

[3] 27365

$ renice 5 27365

27365: old priority 0, new priority 5

$ renice2 27365

renice: 27365: setpriority: Permission denied

Note that the value used with the nice command is the opposite of what you may usually associate with a priority. Put another way, a nice level of 20 results in a process that isn't very nice to its fellow processes, since it's running at a high priority and hogs the CPU.

$ renice -527365

renice: 27365: setpriority: Permission denied

# renice 2 27365

27365: old priority 5, new priority 2

# renice -5 27365

27365: old priority 2, new priority -5

You can also adjust the priority of processes in System Monitor and KSysGuard using the options on the context menu (right-click on the process you wish to adjust).

4.9.3.4. ...starting and managing background processes?

$ xboard &

[21771]

$ mc &

[21783]

$

The shell will display the PID of the background process, then immediately present a new prompt, permitting you to enter additional commands before the background command has finished executing.

You can display background processes using the jobs command:

$ jobs

[1]- Running xboard &

[2]+ Stopped . /usr/share/mc/bin/mc-wrapper.sh

Any program that attempts to communicate through the character interface, such as Midnight Commander ( mc ) in this example, will be stopped. Programs that communicate through the graphical user interface, such as xboard , are free to do so while running in the background.

To put a stopped command in the foreground so that you can interact with it, use the fg command:

$ fg 2

The argument is the job number as reported by the jobs command. You can stop the current foreground process by pressing Ctrl-Z.

To run a stopped process in the background, use the bg command:

$ fg1

xboard

...User presses Ctrl-Z...

[1]+ Stopped xboard

$ jobs

[1]+ Stopped xboard

[2]- Stopped . /usr/share/mc/bin/mc-wrapper.sh

$ bg1

[1]+ xboard &

$

You can use a percent sign and a job number instead of a PID when killing processes:

$ kill%1

$

[3]- Exit 15 xboard

4.9.4. Where Can I Learn More?

The manpages for bash (for job control, including jobs , fg , bg , and the version of kill that is built into bash ), top , ps , and kill

4.10. Remote Management Using SSH

4.10.1. How Do I Do That?

To connect to a Fedora system from another Fedora system (or another Linux system), run the ssh client, providing the remote username and hostname (or IP address) as a single argument ( user @ host ). For example, to log in to a host with the IP address 10.0.0.1 using the user ID jon :

$ ssh jon@10.0.0.1

The authenticity of host '10.0.0.1 (10.0.0.1)' can't be established.

RSA key fingerprint is 1d:dd:20:72:b1:0c:28:90:9a:ff:43:69:03:12:71:02.

Are you sure you want to continue connecting (yes/no)?

yes

Warning: Permanently added '10.0.0.1' (RSA) to the list of known hosts.

jon@10.0.0.1's password:

AnotherSecret

Last login: Tue Oct 25 23:13:40 2005 from london-office

$

The question about the authenticity of the remote host will be asked only the first time you connect. The fingerprint value displayed can be used to verify the identify of the remote host and ensure that you're not being conned by a computer located between you and the computer you're trying to connect to; if you're really paranoid, you can check this value, but for most normal applications this isn't necessary. The fingerprint is cached, though, so if it changes in the future you will be warned. It's necessary to type in yes to confirm that you want to continue connecting; y won't suffice.

Once you are connected to the remote machine, you can use the shell as you normally would.

4.10.1.1. Reducing the use of passwords

To set this up, enter these commands on

the client machine (i.e., the machine from which you will be connecting to the remote host):

$ ssh-keygen -t dsa

Generating public/private dsa key pair.

Enter file in which to save the key (/home/chris/.ssh/id_dsa):

Enter

Enter passphrase (empty for no passphrase):

BigSecret

Enter same passphrase again:

BigSecret

Your identification has been saved in /home/chris/.ssh/id_dsa.

Your public key has been saved in /home/chris/.ssh/id_dsa.pub.

The key fingerprint is:

3a:f7:e8:88:59:fb:56:f7:0f:55:6b:fe:f6:ec:e2:2c chris@super

$ ssh jon@remoteMachine"cat > ~/.ssh/authorized_keys" <~/.ssh/id_dsa.pub

jon@remoteMachine's password:

AnotherSecret

The entire SSH security model revolves around the fact that the private key is private. If you permit access to your private key, the security is completely compromised.

Once the public key is installed on the remote host, you can use the ssh-add command to enter your passphrase: