The ramblings of a computer geek
If you need to SSH to a host but don’t have direct SSH access, you can perform a reverse SSH tunnel. For this you need a host that will except inbound connections to work as a “jump host”, it is possible without it, where you could SSH back to your client computer; however for the … Read more
The Raspberry Pi lacks a real time clock, which means that the time can drift, so much so that NTP fails to update the software clock because its skewed so much. To resolve this you can do the following: Add this to /etc/ntp.conf: tinker panic 0 That will cause ntpd to sync despite the large … Read more
When attempting to use the check_ldap plugin, I found that unsecured LDAP lookups on port 389/TCP worked fine, but attempting a secure lookup on 636 or using TLS failed. Attempting a check_ldap check normally worked fine (i.e. to port 389), but attempting an LDAPS or LDAP TLS check failed with the following error: The check_ldap … Read more
So looking for something to use your Raspberry Pi for? I had a Mk1 Raspberry Pi laying around and thought it might be good to set it up as a SSH gateway, so I could easily and securely access my home machines when out and about. These instructions assume you have a Raspberry Pi which … Read more
To easily find where your disk space is being used from the command line you can use the NCDU utilty. To run this use:
You need to verify that a file cert.pem contains the certificate you expected, to do this you can use this command to view the certificate in plain text with expiry date etc visible.
If you occasionally need to reboot a Linux box as a one off one evening you can perform the following commands using the at command. Note if you set a time that has just past it will perform the reboot the following day. So lets say its 16:15 and you want to schedule a reboot … Read more
This assumes you have a APC Smart-UPS UPS with a Network Management Card, that you have already configured to allow SNMP connections and you’ve configured the community string. This is tested using MRTG running on Ubuntu with an AP9619 network management card in the UPSes. This took ages to find the correct metrics OIDs from … Read more
Firstly you create an image of a disk using dd. Say in this example you have a second harddisk on your comuter called: /dev/sdb you want to make a dd image of it and then verify it is identical to the source disk. Step 1 Create the MD5 hash of the source disk as it … Read more
If you ever need to watch a log file to see if something goes into it, here is a cheeky command to do that. The -f says to watch for updates, the -n 500 shows how many lines to bring back.