System administration

Linux system administration

Mapping iSCSI filesystem mounts on Linux

Creating Your Own SSL Certificate Authority (and Dumping Self Signed Certs)

Network throughput measurement using netcat

SERVER SIDE
nc -v -v -n -l -p 2222 > /dev/null
listening on [any] 2222 …
connect to [127.0.0.1] from (UNKNOWN) [127.0.0.1] 55166
sent 0, rcvd 1073741824

CLIENT SIDE
dd if=/dev/zero bs=$((220)) count=$((210)) | nc -v -v -q 0 127.0.0.1 2222
localhost [127.0.0.1] 2222 (?) open
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.15213 s, 932 MB/s

Network File Transfer using Netcat

Linux tools

• netcat

There are actually two implementations of netcat, the original implementation by *Hobbit* (called netcat-traditional in Debian/Ubuntu) and the OpenBSD implementation (called netcat-openbsd in Debian/Ubuntu). In Debian/Ubuntu the binaries are called nc.traditional and nc.openbsd respectively (and nc is a link to one of those via the alternatives system).
To exec nc.traditional with the name nc:
sudo update-alternatives --config nc

• tcpdump
• Measuring the impact of tcpdump on Very Busy Hosts

Windows system administration

How to map a local folder to a drive letter in Windows
To map a path to a drive letter, you can use either the subst or net use commands from a Windows command line.

subst x: C:\Folder\Example
net use x: \\localhost\c$\Folder\Example

The main difference between the two is that subst expects the location to always be available. If for some reason that location can’t be found, it will try desperately to reconnect at the expense of your computers performance. net use on the other hand is more fault tolerant. When a mapped path appears to be disconnected, it will gracefully disable that mapping until you try to access it again, at which point it will attempt to connect again.