Linux Start Restart and Stop The Cron or Crond Service

Task: Start cron service

To start the cron service, use:
# /etc/init.d/crond start

Task: Stop cron service

To stop the cron service, use:
# /etc/init.d/crond stop

Task: Restart cron service

To restart the cron service, use:
# /etc/init.d/crond restart

If you are using Debian or Ubuntu Linux the following commands.

Task: Debian Start cron service

To start the cron service, use:
# /etc/init.d/cron start
OR
$ sudo /etc/init.d/cron start

Task: Debian Stop cron service

To stop the cron service, use:
# /etc/init.d/cron stop
OR
$ sudo /etc/init.d/cron stop

Task: Debian Restart cron service

To restart the cron service, use:
# /etc/init.d/cron restart
OR
$ sudo /etc/init.d/cron restart

Task : Start the cron service at boot time

It is recommended that you start the service at boot time so that job can run w/o problems.

If you are using Redhat (RHEL)/Fedora Core/Cent OS Linux use the following commands to ensure that the service remains enabled after a reboot:
# chkconfig crond on
You can use a text based GUI tool called ntsysv to enable crond service:
# ntsysv

If you are using Debian or Ubuntu Linux use the following commands to ensure that the service remains enabled after a reboot:
# rcconf
OR
$ sudo rcconf
You can use command line tool update-rc.d:
# update-rc.d cron defaults
OR
$ sudo update-rc.d cron defaults

apt-get install sendmail fails

I was getting an error message when trying to install sendmail on a linux server.

Using the command sudo apt-get install sendmail i was getting the following error:

The following packages have unmet dependencies:
sendmail: Depends: sendmail-bin (= 8.13.8-3) but it is not going to be installed
E: Broken packages

Easy fix, just type:

sudo apt-get install sendmail-bin

press ‘y’ and let that install, then type:

sudo apt-get install sendmail

and it’ll install fine this time! hope this helps someone else out too!

Source: http://hilikusonline.blogspot.com/2009/07/apt-get-install-sendmail-fails.html

How do I download the CD or DVD images to begin my installation of Red Hat Enterprise Linux?

This article describes how to download the CD or DVD ISO images so that you can install Red Hat Enterprise Linux from CD/DVD.

NOTE:

  • Make sure you have at least one valid subscription activated in your RHN account before you begin.
  • If your RHN account only has an activated subscription for Server, you will not be able to download the ISO for Desktop using that account.
  • If you want to download the evaluation version of Red Hat Enterprise Linux, you should submit for an evaluation copy first and then contact your local sales team.
  • CD ISO images are not included in Red Hat Enterprise Linux 6; only DVD ISO images are included. For more installation options on systems without a DVD drive, please refer to the following article: How can I install Red Hat Enterprise Linux 6 without a DVD drive?

The CD and DVD ISO images for Red Hat Enterprise Linux are available here on the Customer Portal.

You can use these images as installation media by burning the ISOs as image files to a DVD or multiple CDs. Most CD/DVD burning applications will have “Burn as ISO” or “Burn as Image” as an option; it is important to use this option to burn the images to disc. You can verify the burn was successful by looking at the CD/DVD contents after the burn is complete. If you see multiple files and directories, the burn was successful. If you only see the filename.iso as the single file on the CD/DVD, then the CD/DVD will not boot and will need to be re-burned as an image file.

Downloading ISO Images

The following steps are recommended for downloading ISO images from RHN:

1) Open a browser and navigate to https://rhn.redhat.com/rhn/software/downloads/SupportedISOs.do, logging in with your Red Hat/RHN Login Credentials. You will see a list of Red Hat Products to which your RHN login is entitled.

2) Select the version you would like to download (for example, “Red Hat Enterprise Linux (v. 5 for 64-bit x86_64)”). Note that there is a separate link for each architecture. If you want to download Desktop for v.5, first check to see if you have the subscription for Desktop activated. If so, the channel for Desktop will be listed on the page.

3) To download the ISO image of the latest release, click the Binary Disc # for CDs or Binary DVD link.

Alternatively, you can copy the download URL and use a command line utility to complete the download. The advantage of using a command line utility like wget is the ability to continue a paused download if a problem is encountered during the download process. To do this, right click the Binary Disc # or Binary DVD link and select Copy link location from the right-click menu. Then use ‘wget -c -O filename.iso http://url/of/iso`, as shown below:

wget -c -O rhel-5-server-x86_64-disc1.iso 
"https://content-web.rhn.redhat.com/rhn/
isos/xxxx/rhel-5-server-x86_64-disc1.isoxxxxxxxx"

NOTE: When using the wget tool to download the package or ISO in RHN, make sure to leave the double quotes around the URL.

If the downloading process pauses or fails, press CTRL+C to terminate the wget process. Then, log into RHN again to obtain a new valid link and run the above command with the new link to continue the download where it left off.

If you use a Windows system to download the ISO, you can download the wget utility from WGET for Windows (win32) – current version: 1.11.4. After that, un-compress wget.exe and put it in c:\windows\sytem32 directory. Then open a command line and use the following command:

wget -c -O rhel-5-server-x86_64-disc1.iso --no-check-certificate 
"https://content-web.rhn.redhat.com/rhn/
isos/xxxx/rhel-5-server-x86_64-disc1.isoxxxxxxxx"

NOTE: When using the wget tool to download the package or ISO in RHN, make sure to leave the double quotes around the URL.

4) After the download is complete, verify the md5sum using the md5sum command:

md5sum filename

NOTE: If you are using a Windows client, you can use the winmd5 utility to check the md5sum.

5) Finally, burn the ISO images to CD/DVD using burning software and use Disc 1 to begin installation for Red Hat Enterprise Linux.

Older Releases

If you want to download an older release, click the Retired tab on the Downloads page and select the desired release.

Add-on Channels / Child Channels

If you wish to download the ISO or related packages from Add-on Channels like RHEL Supplementary or RHEL Extras or any other similar channel, then click the + (plus sign) to list child channels. Below is a screenshot of RHEL Supplementary children.

If you wish to subscribe your system to any of the child channels and install/update packages, then refer to How do I subscribe a system to a sub-channel or a child channel using Red Hat Network (RHN)?

Additional Information