gcc is a GNU project C and C++ compiler for Linux, UNIX, FreeBSD etc. From the wikipedia:
GCC is a key component of the GNU toolchain. As well as being the official compiler of the GNU system, GCC has been adopted as the standard compiler by most other modern Unix-like computer operating systems, including Linux, the BSD family and Mac OS X. GCC has been ported to a wide variety of computer architectures, and is widely deployed as a tool in commercial and closed development environments.
Common gcc options:
cc -E :preprocessor
cc -S :create or show assembly coding
cc -o :object filename
cc -g :debug info
cc -O :optimized code
cc -O2 :optimized code with optimization level increased
cc -Wall :create or show all warning
cc -D_SYMBOL_ : Symbol for prerpcessor
You can use gcc instead of cc.
Under many situations you may need to get a single file/many files from Linux ISO image.
You can mount ISO images via the loop device. You need to use mount command. First login as a root user:
Extract File(s) Under Linux OS
Let us assume that your ISO image name is disk1.iso.
Step # 1: First you need to create a directory /mnt/iso
# mkdir /mnt/iso
# mount -o loop disk1.iso /mnt/iso
Step # 3: Extract file
Now you can easily copy file called file.txt from iso disk image to /tmp directory :
# cd /mnt/iso
# cp file.txt /tmp
Step # 4: Copy foo.rpm from ISO disk image:
# cd /mnt/iso/RedHat/RPMS
# cp foo.rpm /tmp
Extract File(s) Under Windows XP or Vista Os
Windows do not have in built capability as provided by Linux to extract file. Luckly many third party software exist my favorite is Winimage http://www.winimage.com/. Download trial version (Iâ€™m sure you will love to registered this tiny utility later):
1) Install Winimage software
2) Just double click on Linux ISO file
3) Select the desired file and hit CTRL + X (or from Image menu select extract)
For more information read man pages:
Pre login banner is use for sending a warning message before authentication may be relevant for getting legal protection or just give out information to users. The contents of the specified file are sent to the remote user before authentication is allowed. This option is only available for protocol version 2. By default, no banner is displayed (if you are using latest version of Linux/UNIX then you do not have to worry about version issue).
Procedure to change OpenSSH pre login banner
1) By default sshd server turns off this feature.
2) Login as the root user; create your login banner file:
# vi /etc/ssh/sshd-banner
Welcome to nixCraft Remote Login!
3) Open sshd configuration file /etc/sshd/sshd_config using a text editor:
# vi /etc/sshd/sshd_config
4) Add/edit the following line:
5) Save file and restart the sshd server:
# /etc/init.d/sshd restart
6) Test your new banner (from Linux or UNIX workstation or use any other ssh client):
$ ssh firstname.lastname@example.org
Welcome to nixCraft Labs!
vivek@ rh3es.nixcraft.org’s password:
Please note that this feature may not work with third party ssh client such as Putty.
You can make a file immutable on Linux with the help of utility called chattr. One can changes the file attributes on a Linux second extended file system. The operator +
causes the selected attributes to be added to the existing attributes of the files; -
causes them to be removed; and =
causes them to be the only attributes that the files have.
All files accessible in a Linux (and UNIX) system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the file system found on some device to the big file tree.
Use the mount command to mount remote windows partition or windows share under Linux as follows:
Procedure to mount remote windows partition (NAS share)
1) Make sure you have following information:
==> Windows username and password to access share name
==> Sharename (such as //server/share) or IP address
==> root level access on Linux
2) Login to Linux as a root user (or use su command)
3) Create the required mount point:
# mkdir -p /mnt/ntserver
4) Use the mount command as follows:
# mount -t cifs //ntserver/download -o username=vivek,password=myPassword /mnt/ntserver
Use following command if you are using Old version such as RHEL <=4 or Debian <= 3:
# mount -t smbfs -o username=vivek,password=D1W4x9sw //ntserver/download /mnt/ntserver
5) Access Windows 2003/2000/NT share using cd and ls command:
# cd /mnt/ntserver; ls -l
- -t smbfs : File system type to be mount (outdated, use cifs)
- -t cifs : File system type to be mount
- -o : are options passed to mount command, in this example I had passed two options. First argument is password (vivek) and second argument is password to connect remote windows box
- //ntserver/download : Windows 2000/NT share name
- /mnt/ntserver Linux mount point (to access share after mounting)
Updated for accuracy on Aug-8-2007, 8:19PM.
An ISO image is an archive file (disk image) of an optical disc using a conventional ISO (International Organization for Standardization) format. ISO image files typically have a file extension of .ISO. The name “ISO” comes from the ISO 9660 file system used with CD-ROM or DVD media, but an ISO image can also contain UDF file system because UDF is backward-compatible to ISO 9660. You can mount an ISO file or images via the loop device under Linux. It is possible to specify transfer functions (for encryption/decryption or other purposes) using loop device.