What tool do you use to monitor your servers?
I’ve used Nagios in the past with success. It’s very extensible (over 200 add-ons), relatively easy to use and lots of reports. A negative would be the initial setup.
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What are the different widely used RAID levels and when should I consider them?
RAID: Why and When RAID stands for Redundant Array of Independent Disks (some are taught “Inexpensive” to indicate that they are “normal” disks; historically there were internally redundant disks which were very expensive; since those are no longer available the acronym has adapted). At the most general level, a RAID is a group of disks … Read more
Difference between KVM and QEMU
Qemu: QEmu is a complete and standalone software of its own. You use it to emulate machines, it is very flexible and portable. Mainly it works by a special ‘recompiler’ that transforms binary code written for a given processor into another one (say, to run MIPS code on a PPC mac, or ARM in an … Read more
Physically locating the server
Use IPMI to trigger LEDs, increase fan RPMs or sound the beep/alarm. Take a look at the man page for ipmitool https://linux.die.net/man/1/ipmitool depending on the server you may be able to set the LEDs, LCD display, fan RPM offset(listen when nobody is in the office). Some other IPMI or BMC interfaces may allow you to … Read more
How do I view the details of a digital certificate .cer file?
OpenSSL will allow you to look at it if it is installed on your system, using the OpenSSL x509 tool. openssl x509 -in cerfile.cer -noout -text The format of the .CER file might require that you specify a different encoding format to be explicitly called out. openssl x509 -inform pem -in cerfile.cer -noout -text or … Read more
Any benefit or detriment from removing a pagefile on an 8 GB RAM machine?
TL;DR version: Let Windows handle your memory/pagefile settings. The people at MS have spent a lot more hours thinking about these issues than most of us sysadmins. Many people seem to assume that Windows pushes data into the pagefile on demand. EG: something wants a lot of memory, and there is not enough RAM to … Read more
How to include multiple domains in an spf TXT Record
v=spf1 include:_spf.google.com include:otherdomain.com ~all There’s no restriction against including multiple names in a single entry; Hotmail, for instance, takes this to extremes. Note that multiple includes, or nested ones, need to stay under the limit of 10 total DNS lookups for the whole SPF check.
Using DD for disk cloning
dd is most certainly the best cloning tool, it will create a 100% replica simply by using the following command. I’ve never once had any problems with it. dd if=/dev/sda of=/dev/sdb bs=32M Be aware that while cloning every byte, you should not use this on a drive or partition that is being used. Especially applications … Read more
How to use Let’s Encrypt DNS challenge validation?
Currently it is possible to perform DNS validation, also with the certbot LetsEncrypt client in manual mode. Automation is possible as well (see below). Manual plugin You can either perform a manual verification – with the manual plugin. certbot -d bristol3.pki.enigmabridge.com –manual –preferred-challenges dns certonly Certbot will then provide you instructions to manually update a … Read more
Symlink not updating as expected when using an absolute with relative path
Using -f with ln will overwrite any link that was already there, so as long as you have the correct permissions, it should work… It’s always worked for me. What operating system are you using?