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219 - File and directory timestamps in Linux System

Linux keeps 3 timestamps for each file: mtime, ctime, and atime. Most people seem to understand atime (access time), it is when the file was last read.
There does seem to be some confusion between mtime and ctime though. ctime is the inode change time while mtime is the file modification time. "Change"
and "modification" are pretty much synonymous. mtime changes when you write to the file. It is the age of the data in the file. Whenever mtime changes,

218 - APP-FND-00500 noprint

Oracle EBS has the following error when you print out noprint with more than 0 copy.

214 - Reverse mapping on ssh

If you connect a server with ssh, you get an error message sometimes.

# ssh

reverse mapping checking getaddrinfo for failed - POSSIBLE BREAK-IN ATTEMPT!
Last login: Wed Jan 25 09:20:51 2012 from

212 - yum corrupted

You get the following error after execute yum command. Probably yum is corruped.

Error :

Traceback (most recent call last):
  File "/usr/bin/yum", line 28, in ?
    import yummain
  File "/usr/share/yum-cli/yummain.py", line 30, in ?
    from yum import _
ImportError: cannot import name _

Solution :

Update the yum forcefully. You can get the latest yum from net.

211 - iCalendar, CalDAV

iCalendar is a computer file format which allows Internet users to send meeting requests and tasks to other Internet users, via email,
or sharing files with an extension of .ics. Recipients of the iCalendar data file (with supporting software, such as an email client
or calendar application) can respond to the sender easily or counter propose another meeting date/time.

208 - Changing the Number of RHEL 6 (CentOS 6)Desktop Workspaces

By default, RHEL 6 configures two workspaces.

To increase the number of available workspaces :

1. Right click with the mouse on the workspace control in the panel.

2. Select Preferences.

3. Simply increase the Number of workspaces value to the desired number.

The name of each workspace may be changed by double clicking on the default name in the list
(Workspace 1, Workspace 2 etc) and typing in a new name.

207 - portreserve ( to reserver port# in Linux Server )

The portreserve program aims to help services with well-known ports that lie in the portmap range. 
It prevents portmap from a real service's port by occupying it itself, until the real service tells it to release the
port (generally in the init script).

1. Install the package for RedHat / CentOS 6

# yum search portreserve

# yum install portreserve

202 - Required packages for Nagios & CentOS v6

If you install Nagios into CentOS v6, you need the following packages.
Check the packages before the installation.

yum install httpd php
yum install gcc glibc glibc-common
yum install gd gd-devel
yum install openssl-devel


201 - Disable firewall (iptable)

iptables is administration tool / command for IPv4 packet filtering and NAT.

The firewall serves as an antidote to access from unwanted connections. This facility is an important and commonly used in server
environments to restrict any ports that might be accessed, both internally and externally.

To disable the firewall on Red Hat Linux system and its derivatives (Fedora, CentOS, etc) :

As root user >

199 - putty 0.61 : Access Denied Message

It was being caused by GSSAPI authentication. The better option is to set PuTTY not to try using it.

PuTTY options :
Connection -> SSH -> Auth -> GSSAPI
Uncheck the 'Attempt GSSAPI authentication' checkbox.

Other option :
Disabled GSSAPIAuthentication in sshd_config in your Linux Server.
Explicitly disable GSSAPI authentication in SSH client program configuration file, i.e. edit the /etc/ssh/ssh_config and add in this


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by Dr. Radut