.pQd

MySQL on BTRFS?

by .pQd
i’ve been running a set of production MySQL databases on BTRFS since April 2016. BTRFS is not exactly known for its stellar performance when hosting databases or images of virtual machines due to its COW nature. why would i do it then? to have data snapshots and be able to ‘go back in time’ quickly ... Read More

A wall of text on bad and good choices

by .pQd
In this line of work, you don’t just get to play with shiny toys having plenty of blinking lights. There’s plenty of choices to be done nearly every day. Choices or rather bets: some of the technologies, software stacks, products or services provided internally will eventually be a flop. Decisions made over the years are ... Read More

E5-2643 in r620 stuck at a very low cpu frequency

by .pQd
few weeks ago i’ve done a general firmware upgrade of 2 identical Dell Poweredge r620 servers. a while later i’ve noticed that one of them had really sluggish performances. i’ve noticed that /proc/cpuinfo has shown CPU frequencies of hundreds of MHz rather than thousands. cat /proc/cpuinfo |grep MHz gave me 16 rows of values between ... Read More

lxc broken after upgrade from linux-image-4.12.0-0.bpo.1-amd64 to linux-image-4.13.0-0.bpo.1-amd64

by .pQd
lxc containers no longer start after i’ve upgraded debian stretch server from 4.12 kernel from stretch-backports repository to 4.13 also from backports. symptoms in /var/log/syslog: that was resolved by creating /etc/systemd/network/99-default.link with: via this comment. then there was nothing interesting in syslog but the lxc guest still would not start – lxc-start -F -n serverName ... Read More

btrfs and nfs dont play nicely together

by .pQd
i use ghettoVCB to take backups of vmware esxi 6.5 vms. data is copied to a nfs share hosted on Debian Linux. for over a year i used btrfs partition as an underlying datastore for the nfs share. and i just could not get it to work for backups which size larger than available RAM ... Read More

ucarp and vmware esxi

by .pQd
i’ve moved a linux router from 9yo physical box to a vm running under esxi 6.5. it’s a designated master in pair of master / slave managed by ucarp. it took me a while to figure out why it was not working – why didn’t the slave ‘see’ the master machine? as it turned out ... Read More

opendkim failing to start after recent routine debian update

by .pQd
on 2017-10-12 i’ve done a routine apt-get update; apt-get upgrade on a debian stretch vm that, among other services, runs opendkim service that adds a digital signature in the headers of the outgoing mails. during the update i was asked weather to keep or replace the /etc/opendkim.conf; as usual in such cases i’ve answered no ... Read More

bridge on vlans on active-backup bonding under debian stretch

by .pQd
i use this setup for few lxc servers. bonding provides me layer2 failover based on arp probes [ so it’ll work even if switch link stays up yet forwarding fails the mechanism will kick in ]. this is continuation of an earlier post, this time under debian stretch

“out of range” on drac console when booting debian stretch

by .pQd
i’ve installed debian stretch on an old dell poweredge 2950. after booting it i saw grub, few lines from kernel and then green screen with “out of range”: reboot, on the grub menu select “*Debian GNU/Linux”, press e, hilight a line with linux /boot/vmlinuz-4.9.0-3-amd64 root=/dev/sda1 ro quiet, add there vga=normal fb=false nomodeset and press ctrl+x ... Read More

sphinxsearch reborn as manticoresearch?

by .pQd
for the past year number of commits in my favorite open source text-search server – the sphinxsearch project – has dropped to nearly 0. looks like in the meanwhile some of the old contributors moved to another project – manticoresearch. the website of the new project features two prominent supporters – craigslist and boardreader. fingers ... Read More

unwanted wordpress trackback spam

by .pQd
today i’ve learned that disabling trackback in wordpress’s settings > discussion [ ] Allow link notifications from other blogs (pingbacks and trackbacks) on new articles is not enough. your old posts, created before the date when this check-box was un-ticked, will still allow trackback which might be spammy. solution? adjust the trackback setting on per-post ... Read More

varying svn checkout times under virtualized windows server 2016

by .pQd
we’ve set up a new build server using Windows Server 2016 running under ESXi 6.5. few days later devs came back with a complain: full svn checkout time varies a lot – it takes between 1 and 8 minutes. steps taken that hopefully resolved the issue: disable the icon cache of tortoise svn, then eventually ... Read More

bridging two physical interfaces of esxi server

by .pQd
my colleagues got into an unpleasant situation where one of two dedicated servers, running vmware esxi 6.0, rented from a datacenter lost its network connectivity. the datacenter/internet-facing interface is down, hours later, during regular working day, the hosting provider did not react and resolve the problem. maybe the network card died, maybe switch port misbehaves ... Read More

ghettoVCB failing randomly on larger VMs

by .pQd
at work we’re using happily ghettoVCB.sh to back up and restore VMWare ESXi VMs. since a few weeks we’ve started to experience occasional failures of backups, only for one – larger VMs. in the logs produced in /tmp/ghettoVCB-2017-04-xxx.log we got: or after some head scratching, watching at iostat -x 1 and ifstat -b 1 -i ... Read More

simplistic gatekeeper limiting access to apache2-based proxy

by .pQd
i had to expose some web-based application hosted on a windows server to the internet. i don’t put too much trust in the developers of that particular application so i did not want to make it reachable from the public internet. while i could not use ip address based whitelist i could count on the ... Read More

posting a file from command line with CURL

by .pQd
i needed to write a .bat script for windows to upload a log file. quick and nasty hack.. on the sending end: looks straightforward, worked when i tested; but failed to upload in the production setup. on the http server/PHP i was getting: turned out that the log file was growing. curl at the beginning ... Read More

extracting attachments from unix mail files

by .pQd
i log some of the messages passing by Postfix-based relay using always_bcc = bcc@somewhere.com in main.cf. Sometimes – to track spam or problems – i need to check content of the attachments. this comes handy if content is embedded inline i have to edit the file and replace or just add the 2nd part if ... Read More

2 hikes in Hong Kong

by .pQd
i was in HK again; just for a week, but there was enough time during the weekend to hike again in the wildness. High Junk Peak at first i did not enjoy this route at all – just after living the last buildings behind: there was ~25 min of walking up the narrow concrete stairs ... Read More