Multiple buffer overflows were discovered in the Ubuntu Linux kernel and can be corrected by upgrading your system to latest kernel version.
There is a nice utility to monitor hard drive temperature. Most modern x86 computer hard disk comes with S.M.A.R.T (Self-Monitoring, Analysis, and Reporting Technology). It is a monitoring system for computer hard disks to detect and report on various indicators of reliability, in the hope of anticipating failures.
Favorites icon (favicon) file is placed in a web server root directory. It is a page icon or associated with a particular website. For example when you visit our site you see favicon in the browser’s URL bar, next to the site’s name. Also it appears next to the site’s name in lists of bookmarks, and next to the page’s title in a tabbed document interface.
There is a tool called ppmtowinicon which convert 1 or more portable pixmaps into a Windows .ico file You need to specify one or more portable pixmaps as input and it produces a Microsoft Windows .ico file as output. A Windows icon contains 1 or more images, at different resolutions and color depths. Microsoft recommends including at least the following formats in each icon (size and bits-per-pixel):
=> 16 x 16 – 4 bpp
=> 32 x 32 – 4 bpp
=> 48 x 48 – 8 bpp
How to create a favicon.ico with GIMP
You need to install netpbm – a graphics conversion tools under Linux / UNIX. You also need GIMP – the GNU Image Manipulation program to create a favicon on Linux.
Install netpbm and GIMP
Use apt-get command to install packages under Debian / Ubuntu Linux:
$ sudo apt-get install netpbm gimp
Step # 1: Convert logo to ppm raw format
- Open your logo using GIMP
- Now cut and paste logo in square
- Next resize logo by visiting Image > Scale image option. Set pixel size to 16 x 16 or 32 x 32 or 48 x 48.
- Next click on File > Save as > Enter file name as favicon.ppm > Click on Save > Raw Encoding > Ok
Step # 2: Convert portable pixmaps into a Windows .ico file
Now run the following command to create a .ico file:
$ ppmtowinicon -output favicon.ico favicon.ppm
Step # 3: Upload favicon.ico file
Upload favicon.ico file to webserver root directory such as /var/www/html or /srv/httpd/cyberciti.biz.
Step # 4: Favicon example
To activate favicon, modify your site pages or template by placing following code between <head>…</head> section:
<link rel="shortcut icon" href="/favicon.ico" />
So how do you find out how fast is your hard disk under Linux? Is it running at SATA I (150 MB/s) or SATA II (300 MB/s) speed without opening computer case or chassis?
My friend wanted to know how to change or convert DHCP network configuration to static configuration. After initial installation, he wanted to change network settings. Further, his system is w/o GUI system aka X Windows. Here is quick way to accomplish the same:
Your main network configuration file is /etc/network/interfaces
Desired new sample settings:
=> Host IP address 192.168.1.100
=> Netmask: 255.255.255.0
=> Network ID: 192.168.1.0
=> Broadcast IP: 192.168.1.255
=> Gateway/Router IP: 192.168.1.254
=> DNS Server: 192.168.1.254
Open network configuration file
$ sudo vi /etc/network/interfacesOR
$ sudo nano /etc/network/interfaces
Find and remove dhcp entry:
iface eth0 inet dhcp
Append new network settings:
iface eth0 inet static
Save and close the file. Restart the network:
$ sudo /etc/init.d/networking restart
Task: Define new DNS servers
Open /etc/resolv.conf file
$ sudo vi /etc/resolv.conf
You need to remove old DNS server assigned by DHCP server:
Save and close the file.
Task: Test DNS server
$ host cyberciti.biz
Network command line cheat sheet
You can also use commands to change settings. Please note that these settings are temporary and not the permanent. Use above method to make network changes permanent or GUI tool as described below.
Task: Display network interface information
Task: Take down network interface eth0 / take a network interface down
$ sudo ifconfig eth0 downOR
$ sudo ifdown eth0
Task: Bring a network interface eth0 up
$ sudo ifconfig eth0 upOR
$ sudo ifup eth0
Task: Change IP address and netmask from command line
Activate network interface eth0 with a new IP (192.168.1.50) / netmask:
$ sudo ifconfig eth0 192.168.1.50 netmask 255.255.255.0 up
Task: Display the routing table
$ /sbin/route OR
$ /sbin/route -n
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface localnet * 255.255.255.0 U 0 0 0 ra0 172.16.114.0 * 255.255.255.0 U 0 0 0 eth0 172.16.236.0 * 255.255.255.0 U 0 0 0 eth1 default 192.168.1.254 0.0.0.0 UG 0 0 0 ra0
Task: Add a new gateway
$ sudo route add default gw 172.16.236.0
Task: Display current active Internet connections (servers and established connection)
$ netstat -nat
Task: Display open ports
$ sudo netstat -tulpOR
$ sudo netstat -tulpn
Task: Display network interfaces stats (RX/TX etc)
$ netstat -i
Task: Display output for active/established connections only
$ netstat -e
$ netstat -te
$ netstat -tue
- -t : TCP connections
- -u : UDP connections
- -e : Established
Task: Test network connectivity
Send ICMP ECHO_REQUEST to network hosts, routers, servers etc with ping command. This verifies connectivity exists between local host and remote network system:
$ ping router
$ ping 192.168.1.254
$ ping cyberciti.biz
See simple Linux system monitoring with ping command and scripts for more information.
Task: Use GUI (Graphical Configuration) network Tool
If you are new, use GUI configuration tool, type the following command at terminal:
$ network-admin &
Above command is Ubuntu’s GUI for configuring network connections tool.
Final tip – Learn how find out more information about commands
A man page is your best friend when you wanted to learn more about particular command or syntax. For example, read detailed information about ifconfig and netstat command:
$ man ifconfig
$ man netstat
Just get a short help with all command options by appending –help option to each command:
$ netstat --help
Find out what command is used for particular task by searching the short descriptions and manual page names for the keyword:
$ man -k 'delete directory'
$ apropos -s 1 remove
Display short descriptions of a command:
$ whatis rm
$ whatis netstat
Linux offers an excellent collection of utilities, which can be use to finding the files and executables, remember you cannot memorize all the commands and files 😉
You need to use the sudo command to grant a permission to other users to shutdown your server. The sudo command allows a permitted user to execute a command as the superuser or another user, as specified in the /etc/sudoers file. Login as a root user and type the visudo command to edit the sudoers file.
I use ADSL at home via ISP modem. As soon as my eth0 comes up I would like to have my firewall script get executed and setup the iptables firewall rules for me.
Both Debian and Ubuntu Linux provides a number of package management tools. This article summaries package management command along with it usage and examples for you.
FreeBSD comes with kldstat command. The kldstat utility or command displays the status of any files dynamically linked into the kernel. And the kldunload utility unloads a file which was previously loaded with lldload command. You can use kldunload command as follows.
Unload a file from the kernel
First login as a root user (use su – or sudo commnad):
Get list of loaded modules/drivers first use following command
To remove module use the following command
The kldstat utility displays the status of any files dynamically linked into the kernel.
kldunload -i ID
Example to unload smbfs module
Type the following command as the root user:
# kldunload smbfs
# kldunload -i 8
Please note that # 8 is module ID obtained using kldstat command.
Force the unload
You can pass -f option to kldunload to force the unload. This ignores error returns to MOD_QUIESCE from the module and implies that the module should be unloaded even if it is currently in use. The users are left to cope as best they can.
# kldunload -f smbfs
Have you ever wondered why shutdown account exists on Linux server, especially under Red Hat Enterprise Linux distribution?
The answer is quite simple – shutdown account can shutdown server. Here is how you can enable the shutdown account: