====== Technical notes on a variety of topics ====== Many of the following articles contain some of my opinions. If you find you disagree with them, please feel free to publish your own. Some of what follows is also incomplete (occasionally the term "work in progress" is appropriate). I try to mention this at the start of any such article. All articles also have a "last modified" date at the bottom - you may wish to check this in case some of what I have written becomes out of date, simply due to the inexorable passage of time. ===== General stuff ===== * How to show [[.technotes:IP addresses]] in documentation, the right way * A suggestion for [[.technotes:hostnames]] * [[.technotes:nosystemd|Avoiding systemd]] on a Debian (Jessie or later) installation * [[.technotes:Devuan]] - a systemd-free replacement for Debian 8 and later * What to do if your machine gives you a "[[.technotes:GrubRescue|grub rescue>]]" prompt * Making the tab more visible in Konsole (KDE terminal application) when there is [[.technotes:activity]] in the session * Why [[.technotes:devuan:kmail|KMail 2 is shit]] compared to KMail 1 (part of my experience upgrading Debian Wheezy to [[.technotes:Devuan]] Jessie, documented above) * Some of the [[.technotes:WeirdHosting|weird things]] hosting providers do * Some of the [[.technotes:GreatHosting|great things]] hosting providers do * Topping up a [[.technotes:TescoSIM|Tesco pay-as-you-go SIM card]] when it's not in a telephone * Special codes for doing things with an [[.technotes:alditalk|Aldi Talk]] or [[.technotes:nettokom|NettoKom]] (two German supermarket mobile phone service providers) SIM card * Notes on [[.technotes:Debianpreferences|things to do]] to a Debian / Devuan server immediately after installation * Some [[.technotes:Debianinstalls|useful tools]] to install on a Debian / Devuan server which aren't there by default * Setting up "screen" to run as soon as you [[.technotes:ScreenLogin|log in]] to an account * How to identify whether a bash script is being run [[.technotes:localSSHcron|locally, via SSH, or from cron]] * How to keep LVM partitions almost, but not quite, full by [[.technotes:LVMgrow|automatically growing them]] as needed * [[.technotes:ShrinkingEXT|Shrinking]] ext2/3/4 partitions and file systems (and why you probably don't want to) * An Asterisk-based [[.technotes:alarmclock|alarm clock]] system * How to find out which [[.technotes:deb-installed|packages have been installed]] using a backup of a Debian/Devuan system * Notes on [[.technotes:deb-build|what you need to install]] on a Debian / Devuan machine to be able to (re)build packages from source * A script to [[.technotes:SNMPscan|scan your network]] for SNMP managed switches and find out what's connected to which port * Writing a script which will either do something now, or run later, [[.technotes:NowOrLater|when you want it to]] * A few notes on creating an "[[.technotes:InstantVM|Instant VM]]" image which I use to make new virtual servers in under 2 minutes * When will my [[.technotes:Raid]] (re)build be ready? (This turned into a bit of an essay about Raid, [[.technotes:backups and archives]], but never mind...) * Converting [[.technotes:CSV to SQL]] without having to manually create DB tables * Moving or copying [[.technotes:Logical Volumes]] between Volume Groups (and optionally between servers) * Checking lines of code for [[.technotes:mismatched brackets]] * [[.technotes:Routing IPv6]] to/from machines on your internal network (if you have a connectivity provider which does IPv6) * [[.technotes:HaltReboot|Halting or rebooting]] a machine when it really doesn't want to * Running a cron job on [[.technotes:unusualcron|the last Friday of each month]] or something similarly out of the ordinary * [[.technotes:inode|Recovering a file which has been deleted]], but is still being held open by a running process * Using Firefox [[.technotes:cookies]] with wget * Installing the same [[.technotes:packages]] on a Debian/Devuan machine as are installed on another one * A reminder of how to set [[.technotes:printing options]] from the command line * Saving [[.technotes:STDERR]] into a variable whilst getting STDOUT on the screen * Converting a machine with a [[.technotes:ext2lvm|single-partition root FS]] to multiple partitions on LVM ===== Applications ===== * The [[.technotes:Icinga]] monitoring system * [[.technotes:Asterisk]] telephony * A few comments about [[.technotes:FreePBX]] * Good luck with trying to use [[.technotes:Kamailio]] * Getting started with [[.technotes:Foreman]] * Using [[.technotes:iSCSI]] under Debian * Trying to get [[.technotes:Vagrant]] running under Debian * Using [[.technotes:systemimager]] to create virtual machines quickly and easily waste a couple of hours finding out it doesn't work on Debian * Getting a [[.technotes:Fritz!Box]] cable (or probably DSL too) modem talking SIP to an Asterisk server * My experience of using [[https://github.com/twindb/undrop-for-innodb|TwinDB]] to [[.technotes:TwinDB|recover a corrupted MySQL database]] system * Recovering files deleted from an ext3 or ext4 file system [[.technotes:extundelete]] * Running [[.technotes:zoneminder]] in a master-slave arrangement * [[http://Grafana.com|Grafana]] has one of the worst examples of a [[.technotes:grafana|non-intuitive user interface]] I have come across * It also has a [[.technotes:grafanaflash|very distracting flashing symbol]] in the top right of every display box on the dashboard * [[.technotes:telegrafana|Getting data into Grafana]] via Telegraf and InfluxDB * Is [[.technotes:Python|Python stupid]], or is it me? * A few [[.technotes:Kindle|cryptic Kindle notes]] * Some (probably not very useful for anyone else) notes on [[.technotes:sound|getting sound to work]] on my PC * [[.technotes:pdfcrack]] * Using corosync and pacemaker to manage [[.technotes:pacemaker|geo-diverse resources]] without booth * How to install [[.technotes:FreeSwitch]] under Devuan * How to install [[.technotes:FusionPBX]] under Devuan * How to use [[.technotes:usingFreeSwitch|FreeSwitch]] once you've installed it * A reminder (for me, at least) about using [[.technotes:taskjuggler]] * [[.technotes:DRBD]] and [[.technotes:OCFS2]] * Building [[.technotes:Frotz]] under Devuan (and, very probably, Debian as well) * Installing [[.technotes:Homer]] under Devuan and getting it doing something useful * Replicating a [[.technotes:Galera cluster]] with no downtime * Using [[.technotes:ansible]] for configuration management ===== Hardware ===== * Notes about various [[.technotes:VoIP|VoIP phones]] * What to do if your Lego NXT brick is [[.technotes:tickingNXT|ticking quietly with a blank display]] * How to repair a Lego NXT brick whose [[.technotes:NXTdisplay|display is blank]], or flickering * A [[.technotes:LegoSorter|Lego sorting machine]] * Getting a [[.technotes:Dell 1250c]] (or Xerox 6010N; same hardware, different label) working under Debian * [[.technotes:SonoffWifi|Upgrading the firmware]] in an Itead [[https://www.itead.cc/sonoff-pow.html|Sonoff POW]] over wireless * Getting data from a [[.technotes:WithingsWS30|Withings wireless scale]] without letting it talk to the Internet * Working with the [[.technotes:RaspberryZeroW|Raspberry Pi Zero W]], including [[.technotes:RaspberryRootNFS|mounting the root FS over NFS]] (wirelessly, of course) * Installing extra applications on the [[.technotes:Tolino Epos]] eBook reader * Using a [[.technotes:DVBSky T982]] DVB-T / DVB-C receiver / decoder card under Linux * Running a script when a particular [[.technotes:USB device]] is plugged in * Using a [[.technotes:Reolink VLC 422]] camera with zoneminder * Installing Devuan on a [[.technotes:PC Engines APU 4D4]] * Using a [[.technotes:Qualcomm Gobi 1000]] GSM / UMTS modem under Linux (on the above APU 4D4) * [[.technotes:USB3]] controllers ===== Useful information from elsewhere ===== * [[http://markus.wernig.net/en/it/ip6tunnel-ipsec-only.phtml|Tunneling IPv6 over an IPv4 IPsec link]] * The [[http://arbtt.nomeata.de|Automatic Rule-Based Time Tracker]] looks very interesting for tracking time spent on customer projects * [[http://backreference.org/2013/12/23/diskless-iscsi-boot-with-pxe-howto/|Booting a machine with the root file system mounted over iSCSI]] * A list and explanation of [[https://www.linux.org/threads/understanding-the-various-grub-modules.11142/|Grub modules]] * [[https://www.linux-kvm.org/page/Migration|Live migrating]] Qemu / KVM virtual machines * Live migration / HA failover of [[https://rarforge.com/w/index.php/2_Node_Cluster:_Dual_Primary_DRBD_+_CLVM_+_KVM_+_Live_Migrations|KVM virtual machines using DRBD]] * Pretty much [[https://documentation.suse.com/sle-ha/15-SP1/html/SLE-HA-all/cha-ha-clvm.html|more on the same topic]] (newer, I think) * [[https://www.jeffgeerling.com/blogs/jeff-geerling/mysql-select-rows-are-one|Finding data in one MySQL table which isn't in another table]] * [[https://www.rsyslog.com/doc/v8-stable/tutorials/database.html|Writing syslog to a database]] * Using a [[http://www.opensourcepartners.nl/~costar/dylol/|Dymo LabelManager PC]] under Linux * An interesting alternative [[https://hackaday.com/2020/11/05/open-source-lego-controller/|Lego controller]] * Using an IP camera as a [[https://www.linux-projects.org/uv4l/tutorials/turn-mjpeg-stream-into-camera/|video4linux2]] device * Another page about [[https://superuser.com/questions/751568/use-a-ip-camera-as-a-virtual-camera|the same thing]], not sure how different the approach is * Yet another page with [[https://github.com/domagalski/linux-video-streaming|quite a detailed walkthrough]] * [[https://micha.freeshell.org/qic36_qic02|Using a QIC-36/24/02 tape drive under Linux]] ---- [[.:|Go up]]\\ Return to [[:|main index]].