Convert Video info MP4 using ffmpeg

Convert Video For Streaming

if you want to scale the video to specific size, use -vf scale option, example

Inject metadata

See ffmpeg

Cut a Video using ffmpeg

To cut a video using ffmpeg, use

See Install ffmpeg on Ubuntu

lftp Fatal error: Host key verification failed

When i connect to a remote SFTP server using lftp, i get following error

The error is “Fatal error: Host key verification failed.”

To fix this, just SSH into this server with command

See lftp

Using tar over SSH Session

I wanted to make a tar of a folder on a remote server. But the server don’t have much disk space left, so the tar operation failed.

The server had no rsync installed to copy over the folder to another server.

To save generated tar file on another server, i used command


See tar

Zimbra Unable to validate certificate chain

On installing SSL on Zimbra mail server, i get following error

This was due to SSL cert chain. The ca-bundle file they provided did not work with Zimbra. This is due to some issue with the order in witch CA Certificate files are placed. Here is zimba documentaion related to this issue

I checked with SSL provider, they initially provided a combined SSL certificate, that have cert file + ca certificate. I tried to install it, but it did not work.

After showing SSL support the screenshot of the SSL install page, they provided me with 3 differnt files.


In the zimbra SSL install, you have option to add more intermediate CA by clicking “Add Intermediate CA” link.

The provided files are

I tried to install it using UI, but it failed with some error related to RemoteManager and port 22.

To install on Command line, first you need to becom user zimbra

I copied all files provided by SSL provider to the server. Change to SSL folder

Edited the file

Pasted the SSL certificate content to this file. commercial.key file have the private key, this get auto generated during the CSR generation process.

Now i tried mixing those 3 files (CA certs) to create commerical_ca.crt, but it failed to work

After few try, mixing ca certificate in following order got it work.

Now installed SSL with

Now rebooted the server, after reboot SSL worked.


To disable SELinux, edit

Now you need to reboot. If you don’t want to reboot, disable it for current session with

If you use SELinux, you may need to configure it for each applications.

For web server