Commands Directory | Redhat Enterprise linux

Showing posts with label Commands Directory. Show all posts

Showing posts with label Commands Directory. Show all posts

The rsync Utility

The rsync Utility

When developing backup scripts, consider using the rsync utility. The rsync utility allows you to copy from the local system to a remote system or copy between two local directories. If the files exist in the destination directory, rsync only transfers the differences in the files, which is ideal for backups. The rsync RPM package is required and should already be installed on your system.

After the rsync command-line arguments are listed, the first directory listed is the source, and the second directory listed is the destination. If either directory is preceded by a hostname and a colon (:), the directory is a remote directory. For example, to transfer all home directories to the backup/ directory on the remote server backup.example.com:

The tar Utility and compression

The tar Utility

When backing up data that is no longer being used or data that is not frequently changed, consider creating a compressed archive file using the tar archive utility in combination with one of the compression tools such as gzip or bzip2. Creating a compressed archive file results in one file that must be decompressed and unarchived before files can be restored from it. The compression of the files saves room on the backup media. To use tar, the tar RPM package must be installed. It should be installed on your system unless you chose to only install a specific set of packages. The tar utility does not preserve access control lists.

How to Listing USB Devices

Because USB devices are connected to a separate controller, a different command, lsusb, must be used to list them. The lsusb utility is provided by the usbutils package. Install this package via Red Hat Network.

If executed without arguments, the lsusb command displays each USB bus and any devices attached to them on a separate line as shown.

USB Device List

Bus 002 Device 001: ID 0000:0000

Bus 003 Device 001: ID 0000:0000

Bus 004 Device 001: ID 0000:0000

Bus 005 Device 001: ID 0000:0000

How to Listing PCI Devices

Many devices such as network and video cards are attached to the PCI bus. It is important that the operating system load the correct driver for each device so that the proper device settings are configured. For example, if your server contains a Gigabit network card connected to a Gigabit network switch, you can use a few simple Linux utilities to verify and, if necessary, change the transfer rate of the NIC.

To list all the PCI buses on the system and all the devices attached to them, use the lspci utility from the pciutils package. Install this package via Red Hat Network.

Understanding How RPM Works

How does RPM work? Each software program consists of files and directories, most of which must be located in a particular place on the filesystem. If the software program is distributed in RPM format, these files are compressed together into one RPM file along with instructions on where the files should be located on the filesystem and any additional scripts or executables that must be run before or after the files are installed. These RPM files are often referred to as packages.

A software program, such as the Firefox web browser, might consist of one RPM file. However, some programs are divided into multiple RPM files to allow the administrator to customize which parts are necessary for the system’s usage. For example, the GNOME graphical desktop is divided into many packages that contain parts of the overall desktop.

How to Finds File in linux

There are two invaluable commands that can be used to find files on the filesystem: locate and find. The locate command is the easier of the two to use. Just type the command followed by part or all of the filename you are searching for such as locate .odt to find all OpenOffice.org text files or locate compare to find all filenames that contain the word compare. Notice that no wildcard characters are used. It is assumed that what you type may only be part of the filename you are looking for.

The only catch to this command is that it relies on the generation of a database file so it can quickly display results. The locate command is provided by the mlocate package, which also provides the cron script /etc/cron.daily/mlocate.cron to

How to Find Commands

If you know a command exists on the system but keep getting the error message command not found, check to make sure you are typing the command correctly. Otherwise, it might not be in your PATH environment variable. To view the value of your PATH, execute the command echo $PATH from the command line. As you can see, your PATH is a list of directories. When you execute a command without providing its full path, it must be in one of the directories listed in your PATH. Otherwise, the command not found error is displayed. You can provide the full path to the command if you know it, such as /sbin/lspci to execute the command to list the PCI devices. If you use the command often, but it is not in your PATH, you can add the directory to your PATH.

wget Command

NAME

Wget - The non-interactive network downloader.

SYNOPSIS

wget [option]... [URL]...

DESCRIPTION

GNU Wget is a free utility for non-interactive download of files from the Web. It supports HTTP, HTTPS, and FTP protocols, as well as retrieval through HTTP proxies.

echo Command

NAME

echo - display a line of text

SYNOPSIS

echo [SHORT-OPTION]... [STRING]...

echo LONG-OPTION

DESCRIPTION

Echo the STRING(s) to standard output.

login Command

NAME

login - sign on

SYNOPSIS

login [ name ]

login -p

login -h hostname

login -f name

DESCRIPTION

login is used when signing onto a system. If an argument is not given, login prompts for the username. If the user is not root, and if /etc/nologin exists, the contents of this file are printed to the

umount Command

NAME

umount - unmount file systems

SYNOPSIS

umount [-hV]

umount -a [-dflnrv] [-t vfstype] [-O options]

umount [-dflnrv] {dir|device}...

DESCRIPTION

The umount command detaches the file system(s) mentioned from the file hierarchy. A file system is specified by giving the directory where it has been mounted. Giving the special device on which the file system lives may also work, but is obsolete, mainly because it will fail in case this device was mounted on more than one directory.

mount Command

NAME

mount - mount a filesystem

SYNOPSIS

mount [-lhV]

mount -a [-fFnrsvw] [-t vfstype] [-O optlist]

mount [-fnrsvw] [-o option[,option]...] device|dir

mount [-fnrsvw] [-t vfstype] [-o options] device dir

DESCRIPTION

All files accessible in a 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 filesystem found on some device to the big file tree. Conversely, the umount(8) command will detach it again.

The standard form of the mount command, is

mount -t type device dir

This tells the kernel to attach the filesystem found on device (which is of type type) at the directory dir. The previous contents (if any) and owner and mode of dir become invisible, and as long as this filesystem remains mounted, the pathname dir refers to the root of the filesystem on device.

The listing and help

Three forms of invocation do not actually mount anything:

mount –h prints a help message

mount –V prints a version string

mount [-l] [-t type] lists all mounted filesystems (of type type). The option -l adds the labels in this listing. See below.

ejact Command

NAME

eject - eject removable media

SYNOPSIS

eject -h

eject [-vnrsfmqp] [<name>]

eject [-vn] -d

eject [-vn] -a on|off|1|0 [<name>]

eject [-vn] -c slot [<name>]

eject [-vn] -i on|off|1|0 [<name>]

eject [-vn] -t [<name>]

eject [-vn] -T [<name>]

eject [-vn] -x <speed> [<name>]

eject [-vn] -X [<name>]

eject -V

DESCRIPTION

Eject allows removable media (typically a CD-ROM, floppy disk, tape, or JAZ or ZIP disk) to be

Cal Command

NAME

cal - displays a calendar

SYNOPSIS

cal [-smjy13] [[[day] month] year]

DESCRIPTION

Cal displays a simple calendar. If arguments are not specified, the current month is displayed. The options are as follows:

-1 Display single month output. (This is the default.)

-3 Display prev/current/next month output.

-s Display Sunday as the first day of the week.

-m Display Monday as the first day of the week.

-j Display Julian dates (days one-based, numbered from January 1).

-y Display a calendar for the current year.

-V Display version information and exit.

Cat Command

NAME

cat - concatenate files and print on the standard output

SYNOPSIS

cat [OPTION]... [FILE]...

DESCRIPTION

Concatenate FILE(s), or standard input, to standard output.

-A, --show-all equivalent to -vET

-b, --number-nonblank number nonempty output lines

-e equivalent to –vE

-E, --show-ends display $ at end of each line

-n, --number number all output lines

Touch Command

NAME

touch - change file timestamps

SYNOPSIS

touch [OPTION]... FILE...

DESCRIPTION

Update the access and modification times of each FILE to the current time. A FILE argument that does not exist is created empty, unless -c or -h is supplied.

A FILE argument string of - is handled specially and causes touch to change the times of the file associated with standard output.

Mandatory arguments to long options are mandatory for short options too.

mkdir Command

NAME

mkdir - make directories

SYNOPSIS

mkdir [OPTION]... DIRECTORY...

DESCRIPTION

Create the DIRECTORY(ies), if they do not already exist. Mandatory arguments to long options are mandatory for short options too.

rm Command

NAME

rm - remove files or directories

SYNOPSIS

rm [OPTION]... FILE...

DESCRIPTION

This manual page documents the GNU version of rm. rm removes each specified file. By default, it does not remove directories.

If the -I or --interactive=once option is given, and there are more than three files or the -r, -R, or - -recursive are given, then rm prompts the user for whether to proceed with the entire operation. If the response is not affirmative, the entire command is aborted. Otherwise, if a file is unwritable, standard input is a terminal, and the -f or --force option is not given, or the -i or --interactive=always option is given, rm prompts the user for whether to remove the file. If the response is not affirmative, the file is skipped.

mv Command

NAME

mv - move (rename) files

SYNOPSIS

mv [OPTION]... [-T] SOURCE DEST

mv [OPTION]... SOURCE... DIRECTORY

mv [OPTION]... -t DIRECTORY SOURCE...

DESCRIPTION

Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY. Mandatory arguments to long options are mandatory for short options too.

--backup [=CONTROL] make a backup of each existing destination file

-b like --backup but does not accept an argument

-f, --force do not prompt before overwriting

CP Command

NAME

cp - copy files and directories

SYNOPSIS

cp [OPTION]... [-T] SOURCE DEST

cp [OPTION]... SOURCE... DIRECTORY

cp [OPTION]... -t DIRECTORY SOURCE...

DESCRIPTION

Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY. Mandatory arguments to long options are mandatory for short options too.

-a, --archive same as -dR --preserve=all

--backup[=CONTROL] make a backup of each existing destination file

-b like --backup but does not accept an argument

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