Reread partition table without rebooting?
IMHO the most reliable/best answer is partprobe /dev/sdX
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How to inspect remote SMTP server’s TLS certificate?
You can use OpenSSL. If you have to check the certificate with STARTTLS, then just do openssl s_client -connect mail.example.com:25 -starttls smtp or for a standard secure smtp port: openssl s_client -connect mail.example.com:465
How to get a .pem file from ssh key pair?
According to this, this command can be used: ssh-keygen -f id_rsa -e -m pem This will convert your public key to an OpenSSL compatible format. Your private key is already in PEM format and can be used as is (as Michael Hampton stated). Double check if AWS isn’t asking for a (X.509) certificate in PEM … Read more
Is a CNAME to CNAME chain allowed?
From RFC 1034 – Domain names – concepts and facilities: Domain names in RRs which point at another name should always point at the primary name and not the alias. This avoids extra indirections in accessing information. For example, the address to name RR for the above host should be: 52.0.0.10.IN-ADDR.ARPA IN PTR C.ISI.EDU rather … Read more
Vagrant / VirtualBox DNS 10.0.2.3 not working
You can work around this issue in one of two ways, both of which are in the VirtualBox manual: Enabling DNS proxy in NAT mode The NAT engine by default offers the same DNS servers to the guest that are configured on the host. In some scenarios, it can be desirable to hide the DNS … Read more
Software vs hardware RAID performance and cache usage
In short: if using a low-end RAID card (without cache), do yourself a favor and switch to software RAID. If using a mid-to-high-end card (with BBU or NVRAM), then hardware is often (but not always! see below) a good choice. Long answer: when computing power was limited, hardware RAID cards had the significant advantage to … Read more
Making `wget` not save the page
You can redirect the output of wget to /dev/null (or NUL on Windows): wget http://www.example.com -O /dev/null The file won’t be written to disk, but it will be downloaded.
10 servers to administer and I’m a history major [closed]
Honestly, I would find another job, unless your current task is just to keep everything running until they hire a new SysAdmin. You are being setup for failure. You are doing the job of at least two people if this is all hosted locally and nothing is documented. Don’t worry about the scripting or programming … Read more
Best system administrator accident [closed]
I had fun discovering the difference between the linux “killall” command (kills all processes matching the specified name, useful for stopping zombies) and the solaris “killall” command (kills all processes and halts the system, useful for stopping the production server in the middle of peak hours and getting all your co-workers to laugh at you … Read more
What is the difference between service and systemctl?
service is an “high-level” command used for starting and stopping services in different unixes and linuxes. Depending on the “lower-level” service manager, service redirects on different binaries. For example, on CentOS 7 it redirects to systemctl, while on CentOS 6 it directly calls the relative /etc/init.d script. On the other hand, in older Ubuntu releases … Read more