XMPP audio and video calls

Ejabberd has supported STUN/TURN for quite some time now, this in conjunction with client support can be used to implement one on one audio and video calls. Since version 2.8.0 Conversations Android client added audio and video call functionality by leveraging on STUN/TURN and XEP-0215. The rest of the XMPP world is following the route opened by them, so I expect to see IOS and regular computer XMPP clients to finally implement these new features too in the upcoming months. …

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Disable head parking Western Digital drives

Most Western Digital hard drives’ firmware let the heads park themselves after a certain amount of seconds in case the disk is not actively performing any operation. This might be useful to keep power consumption under control but is actually harmful for disks that run 24/7 (WD Red for example). Luckily there is a way to disable head parking, this can be done directly from Linux using a tool called idle3ctl. …

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Remotely unlock a full disk encrypted Fedora/CentOS server

The idea here is to be able to power on and unlock a remote Full Disk Encrypted (FDE from now on) server. I will leave the how “remotely power on” to the reader to figure out and focus on the other part. The easiest way to accomplish it is by using a program called: dracut-crypt-ssh. $ yum install dropbear dracut dracut-network openssh libblkid-devel gcc $ git clone https://github.com/dracut-crypt-ssh/dracut-crypt-ssh.git $ cd dracut-crypt-ssh $ . …

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Resize QCOW2 disk image

QCOW2 disk images can be easily grown using libvirt command line utils. Unfortunately it isn’t possible to grow QCOW2 images in-place or online. First of all, power off the virtual machine, grow the file and make a copy of it: $ qemu-img resize image.qcow2 +200G $ cp image.qcow2 image-new.qcow2 Identify the specific partion you intend to grow: $ virt-filesystems -a image.qcow2 -l Name Type VFS Label Size Parent /dev/sda1 filesystem ext4 - 536870912 - /dev/sda3 filesystem xfs - 45885612000 - Expand the actual partition: …

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Nginx and XMPP over TLS

XMPP over TLS (formerly XEP-0368) is a clever mechanism that allows users to connect to a XMPP server from networks that restrict outgoing traffic only to specific ports; this block is circumvent by routing XMPP traffic via port TCP 433. If the server hosts only a XMPP server setting up XMPP over TLS is pretty easy, just instruct the server to listen on port 443. If the server also runs a webserver which is listening on port 443 things are a bit more complicated; luckily Nginx provides a way to manage XMPP traffic and redirect it to the XMPP server. …

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Remote encrypted backup with iSCSI and LUKS2

The idea here is to have a LUKS2 encrypted volume stored on a remote server that allows authenticated clients to load and decrypt the data without letting the server know what is being written, read and stored. Keep in mind that this solution is not 100% bulletproof, you still kind of have to trust the backup server because a malicious entity might take multiple snapshots of the encrypted iSCSI LUN and try to crack the encryption. …

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Generate a secure SSH key

In Fedora, CentOS and probably many other Linux distros ssh-keygen; still defaults to RSA 2048. People have not yet realized that the newer, and also faster, elliptic curve cryptography is available; even between my peers I still see that many of them are using old and insecure RSA based keys. Since SSH clients support multiple keys transitioning to newer keys can be painless: create a new elliptic curve key; do not delete the old RSA key; once you login into a server swap the old key with the new one. …

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Configure apcupsd on CentOS

Apcupsd is a powerful daemon that can be used to manage APC UPS, add epel repositories and run: $ yum install apcupsd To configure apcupsd edit the following file: cat /etc/apcupsd/apcupsd.conf" --- ## apcupsd.conf v1.1 ## # # for apcupsd release 3.14.14 (31 May 2016) - redhat # # "apcupsd" POSIX config file # # Note that the apcupsd daemon must be restarted in order for changes to # this configuration file to become active. …

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