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Cron jobs in Linux

To create cron jobs in Linux:

Just remember the following syntax
.—————- minute (0 – 59)
| .————- hour (0 – 23)
| | .———- day of month (1 – 31)
| | | .——- month (1 – 12) OR jan,feb,mar,apr …
| | | | .—- day of week (0 – 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
| | | | |
* * * * * user-name command to be executed
1. run crontab -e
and append your command/tasks as following
* * * * * python /etc/

2. can also edit crontact file directly
vim /etc/crontab and append your tasks
* * * * * root touch filename

To view view cron jobs in Linux:

$ crontab -l

$ cat /etc/crontab



How to burn ISO file using ‘dd’ on USB drive

Using simple dd command we can copy ISO file directly USB drive
# dd if=input_file.ISO of=usb_drive_path

To speed up transfer we can increase block size
# dd bs=8192 if=input_file.ISO of=usb_drive_path

To view progress of the transfer
Method 1 (requires GNU Coreutils 8.24+ – Ubuntu 16.04+ ):
# dd bs=8192 if=input_file.ISO of=usb_drive_path status=progress

Method 2 – using pipe viewer
# dd bs=8192 if=input_file.ISO | pv | ds of=usb_drive_path status=progress

To get time estimation based on a file size
# dd bs=8192 if=input_file.ISO | pv -s 4G| ds of=usb_drive_path status=progress

using ‘watch’

How to exclude packages from update Red Hat/Centos

Sometimes you only want to update packages without upgrading kernel, there are two ways of doing this:

1. Temporarily
# yum update –exclude=<package_name>
# yum update –exclude=kernel*

2. To make it more permanent edit /etc/yum.conf file and append “exclude” keyword
exclude=kernel* redhat-release*

Full column width in PowerCLI

In order to view the full column output in PowerCLI we need to format table appropriately e.x.

PS C:\> Get-VM  | Format-Table -AutoSize -Wrap

Formats the output as a table.

-AutoSize [<SwitchParameter>]
Adjusts the column size and number of columns based on the width of the data. By default, the column size and number are determined by the view.

-Wrap [<SwitchParameter>]
Displays text that exceeds the column width on the next line. By default, text that exceeds the column width is truncated.

Expand Logical Volume in Red Hat VMware

After adding a separate disk run to verify if the space was added:

  1. fdisk -l
  2. create a new partition fdisk /dev/sdb
    1. p – to print current partition table
    2. n – to create a new partition
    3. p – for primary
    4. 1 – depending on the output of the partition table output
    5. press return two times to accept the defaults (first and last sector)
    6. t – to change the system’s partition ID
    7. 8e – to change to Linux LVM
    8. w – to write the changes
  3. restart VM
  4. fdisk -l – to verify that partition was successfully created
  5. convert a partition to physical volume
    $ pvcreate /dev/sdb1
    Physical volume “/dev/sdb1” successfully created
  6. Extend current volume group
    vgextend rhel /dev/sdb1
    Volume group “rhel” successfully extended
  7. Run vgdisplay to verify if free space was added
    vgdisplay rhel | grep “Free”
    Free  PE / Size       4095 / 16.00 GiB
  8. extend logical volume with free space
    lvextend -l +100%FREE /dev/rhel/root
    Extending logical volume root to 66.00 GiB
    Logical volume root successfully resized
  9. Expand ext3 file system online inside of Logical Volume
    xfs_growfs /dev/rhel/root – Red Hat 7
    ext2online /dev/rhel/root
    resize2fs /dev/rhel/root

No Valid Subscription message from Proxmox server

You do not have a valid subscription for this server. Please visit to get a list of available options.

  1. One way of removing the message is to purchase a subscription.
  2. Modify subscrption configuration file
    1. SSH to proxmox server
    2. Create a backup of the existing subscription checkup file
      # cp /usr/share/pve-manager/ext4/pvemanagerlib.js /usr/shar e/pve-manager/ext4/pvemanagerlib.js.orig
    3. Edit pvemanagerlib.js file
      # vim /usr/share/pve-manager/ext4/pvemanagerlib.js
    4. In “checked_command” function search for if (data.status !== ‘Active’) { and change to if(false) {
    5. Save and exit the file
    6. Clear your browsing data and log back in to the proxmox server the message will not pop-up anymore.

SQL2547N while restoring database on DB2 10.5

While restoring database from DB2 9.7 to DB2 10.5 I encountered the following error:


The database was not restored because the backup image is from a previous release and requires rollforward recovery.


I ran the DB2 check backup command db2ckbkp -h <backup_file_name>.001

And resulted with:
[1] Buffers processed: #################

Image Verification Complete – successful.


To resolve the problem a new OFFLINE backup is needed, power down your db instance and take a new backup.

Setup Proxy in SUSE/VCSA

To setup proxy manually in VCSA 5.5 login as root and look into the following file:



HTTP_PROXY=”http://<IP address or FQDN>:<port_number>”

HTTPS_PROXY=”http://<IP address or FQDN>:<port_number>”

FTP_PROXY=”http://<IP address or FQDN>:<port_number>”



If you need to authenticate via proxy

Create a file in your home directory,

/root/.curlrc with permissions 644

and contain the following:

# Proxy credentials

proxy-user = “<username>:<password>”

source the file to apply the changes

source /root/.curlrc