A system engineer's notes: Linux

Showing posts with label Linux. Show all posts

Friday, 14 August 2020

Generate .pem file from .ppk file

Introduction

I recently came across a requirement from our DBA Team wherein they needed to access a server on Oracle Cloud and all they had was a .ppk file received from the App Team that managed the OCI server. Since the source server from which we had to connect did not have a GUI, we needed to generate a corresponding .pem file to use on the command line.

For this, I installed putty on a lab machine.

yum install putty

I then used the .ppk file to generate a .pem file using the following command:

puttygen oci.ppk -O private-openssh -o oci.pem

This step did prompt me for the passphrase for the .ppk file which I was are of.

To login to the OCI server, I used .pem file by specifying the -i option with the ssh command as follows.

-bash-4.1$ ssh -i oci.pem opc@11.59.17.209

Enter passphrase for key 'oci.pem':

Last login: Thu Aug 13 07:17:30 UTC 2020 from 10.22.88.26 on pts/0

Last login: Thu Aug 13 07:18:17 2020 from 10.22.88.26

The passphrase was the same one I was prompted for while generating the .pem file.

Conclusion

This concludes this post on how to generate a .pem file from a .ppk file. I hope you found the post to be useful.

Tuesday, 19 February 2019

Troubleshooting disk addition in multipath configuration in Linux

Introduction
Let me start by saying that the issue in this scenario was actually the result of a human error but I would still like to share the setup and steps I followed that finally helped me understand the problem and eventually resolve it.

The scenario
We received a new LUN of size 64GB from our storage team and it was to be scanned on the server, added to the multipath configuration and subsequently be used within LVM.

Step 1: Detect new disk
I executed the scsi-rescan -r and rescan-scsi-bus.sh commands so that the disk gets detected by the OS. I then used a script to get the disk device name to get the disk WWID mapping. The was basically a wrapper around the scsi_id command. For example:

[ssuri@example:~] $ sudo scsi_id -g -u -d /dev/sdamd
36005076801810718a800000000002a3b
[ssuri@example:~] $

Step 2: Add disk to udev and multipath
The disk was intended to be used for the /grid file system on a DB node. So I added the following lines in the /etc/udev/rules.d/99-dell-oracle-asm.rules file

KERNEL=="dm-*", PROGRAM="scsi_id --page=0x83 --whitelisted --device=/dev/%k", RESULT=="36005076801810718a800000000002c12", OWNER="root", GROUP="root"
ENV{DM_NAME}=="grid_pv1", OWNER="root", GROUP="root"

I wanted the disk alias name to be grid_pv1 and so I proceeded to add the corresponding entry in the /etc/multipath.conf file. I first added a line for the disk WWID in the blacklist_exceptions stanza.

wwid "36005076801810718a800000000002c12"

I then added the below stanza for the grid_pv1 disk in the multipaths stanza.

multipath {

uid 0

gid 0

wwid "36005076801810718a800000000002c12"

alias grid_pv1

mode 0600

}

I then reloaded the required services with the following commands:

/sbin/service multipathd reload

/sbin/udevadm control --reload-rules

/sbin/udevadm trigger --type=subsystems --action=change

/sbin/udevadm trigger --type=devices --action=change

Step 3: Check that disk is visible in multipath configuration

After doing all the above, to my astonishment I could not see the disk in the multipath -ll output. I frantically rescanned the disk again, removed and added the udev and multipath configuration and reloaded the services numerous times. What finally caught my eye was when I saw that the disk was showing up as being blacklisted in the multipath -v3 command output.

[ssuri@example:/var/ ] $ sudo multipath -v3 | grep -i 36005076801810718A800000000002c12

Feb 16 05:56:30 | sdbgs: uid = 36005076801810718a800000000002c12 (callout)