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nixCraft FAQ Roundup June 07, 2007

Recently updated/posted Linux and UNIX FAQ (mostly useful to Linux/UNIX new administrators or users) :


nixCraft FAQ Roundup May 14, 2007

Recently updated/posted Linux and UNIX FAQ (mostly useful to Linux/UNIX new administrators or users) :


nixCraft FAQ Roundup May 06, 2007

Recently updated/posted Linux and UNIX FAQ (mostly useful to Linux/UNIX new administrators or users) :


yum (Yellow dog Updater Modified) is a package manager for RPM compatible Linux systems such as CentOS, Fedora core and latest Redhat Enterprise Linux.

So how do you use yum to update / install packages from an ISO of CentOS / FC / RHEL CD?

Creation of yum repositories is handled by a separate tool called createrepo, which generates the necessary XML metadata. If you have a slow internet connection or collection of all downloaded ISO images, use this hack to install rpms from iso images.

Step # 1: Mount an ISO file

Type the following command (replace iso file name with the actual iso file):
# yum install createrepo
# mkdir -p /mnt/iso/{1,2,3}
# mount -o loop /path/to/centos1.iso /mnt/iso/1

Step # 2: Create a repository

Use createrepo to generate the necessary XML metadata. Type the following commands:
# cd /mnt/iso
# createrepo .

Clean repo, enter:
# yum clean all

Step # 3: Create config file

You need to create a repo config file in /etc/yum.repos.d/ directory.
# vi /etc/yum.repos.d/iso.repo
Append following text:
[My ISO Repository]

Save and close the changes.

Now use yum command to install packages from ISO images:
# yum install package-name

As most of you may know to how extract a tarballs and/or a zip files. Someone, recently PM me with a question:

Dear nixCraft,

How do I extract an RPM package file without installing it on my Fedora Linux or CentOS or RHEL (Red Hat Enterprise Linux) Suse Linux?


CentOS user.

[click to continue…]

Install PHP 5 on Red Hat Enterprise Linux version 4

It appears that many people or sys admin want to run php 5 on Red Hat Enterprise Linux. Unfortunately Redhat does not provide this package (RPM file) for RHEL. You can download source code and install php 5 from official php site. This requires compiler collection on your system. Download source code and just follow instructions presented in INSTALL or REDME file.

Another option is search and installs PHP 5 packages. You can download x86_64 PHP 5 package here. Use wget command to download these packages and rpm command to install new packages. But first remove old php4 package using rpm -e command.

Alert: This post is outdated. Please use the latest version of RHEL/CentOS v6.x+ for PHP 5.x. The author no longer support php 5 rpm on RHEL 4.x.

However these rpm packages 64 bit so if you are running 32 bit os rebuild RPM file.

Step # 1: Download src rpm

# cd /tmp
# wget http://www.cyberciti.biz/files/lighttpd/rhel4-php5-fastcgi/php-5.1.4-1.esp1.src.rpm
# rpm -ivh php-5.1.4-1.esp1.src.rpm

Step #2: Rebuild RPM for 32 bit RHEL version

# cd /usr/src/redhat/SPECS
# rpmbuild -bb php.spec

It will take some time to compile and rebuild RPM files.

Step #3: Install new php5 RPM file

Remove old php4 rpm. Go to /usr/src/redhat/RPMS directory and install PHP5 RPM files.

Please note that PHP 5 is not official supported by Red Hat on RHEL 4.0. You are using these packages on your own risk ;)

Linux : How to delete file securely

Recently we had lot of discussion regarding this issue. How to remove files securely so that it cannot be undeleted. Peter Gutmann paper "Secure Deletion of Data from Magnetic and Solid-State Memory" has very good information. Here are some commands/tools available under Debian GNU/Linux (it should work with other Linux distributions) to delete file securely.

srm: Securely remove files or directories

This command is a replacement for rm command. It works under Linux/BSD/UNIX-like OSes. It removes each specified file by overwriting, renaming, and truncating it before unlinking. This prevents other people from undelete or recovering any information about the file from the command line. Because it does lots of operation on file/directory for secure deletion, it also takes lot of time to remove it. Download srm from http://sourceforge.net/projects/srm (RPM file is also available for RPM based Linux distributions)

i) Untar and install the srm:

# ./configure
# make
# make install 

ii) How to use srm?
srm syntax is like rm command. Read man srm. Here is simple example:

$ srm privateinfo.doc

wipe: It is a secure file wiping utility

Download wipe from http://wipe.sourceforge.net/
i) Untar and install the wipe

# ./configure
# make
# make install

ii) How to use wipe?

$ wipe filename

Read man page of wipe for information.

shred: Delete a file securely, first overwriting it to hide its contents.

It is available on most of Linux distributions including Debian GNU/Linux. To remove file called personalinfo.tar.gz :

$ shred -n 200 -z -u  personalinfo.tar.gz


  • -n: Overwrite N (200) times instead of the default (25)
  • -z: Add a final overwrite with zeros to hide shreddin
  • -u: Truncate and remove file after overwriting

Read the man page of shred(1) for more information. Most of these utilities are not effective (read as useless) only if :

  • File system is log-structured or journaled filesystems, such as JFS, ReiserFS, XFS, Ext3 etc
  • Your filesystems is RAID-based, compressed filesystem etc
  • In addition, file system backups and remote mirrors may contain copies of the file that cannot be removed by these utilities.

See also: