bridging lan segments across untrusted links

we’ve run out of the office space in one of the locations. in short term it was not possible to find a suitable and large enough place to rent so we had to split and relocate some of the staff to another building few kilometers away. it’s possible that we’ll shuffle people and servers between …

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multi-master mysql replication with servers on 3 different continents

at work i’m using mysql replication quite extensively. first it was a straightforward one-way replication that has been rock-solid for us since 2009. in 2012, for another type of data, we’ve started using master-master setup. initially the servers were in different European countries, eventually the secondary site was moved to North America while primary one …

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

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 …

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

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 …

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btrfs and nfs dont play nicely together

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 …

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

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 …

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sphinxsearch reborn as manticoresearch?

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 …

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unwanted wordpress trackback spam

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 …

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varying svn checkout times under virtualized windows server 2016

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 …

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bridging two physical interfaces of esxi server

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 …

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posting a file from command line with CURL

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 …

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extracting attachments from unix mail files

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 …

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bind9 on debian jessie ignores -4 in /etc/default/bind9 and tries to make lookups via ipv6

while checking one of the servers running debian jessie i’ve noticed that logs are full of: strange… didn’t i put “-4” in the /etc/default/bind9 ages ago? apparently i did but ps shows that it was ignored: a bit of googling told me it’s a known problem with systemd [sic!] – the /etc/default/bind9 is ignored. workaround? …

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sphinx search 2.2.11 – column count does not match schema (expected 3, got 2)

i have a real-time sphinx that was configured in this way:\ it was updated using REPLACE INTO myrt VALUES(?,?)… until the day i’ve upgraded to 2.2.11. the update command started to give me: after a bit of investigation i’ve discovered that: with RT index it’s obligatory to have at least one attribute [not id], even …

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dlink DXS-1210-12TC – web interface hanging

i’ve made a mistake again and bought a ‘cheap’, smart-managed network switch. dlink DXS-1210-12TC with 12 10gbase-t ports. and i got punished nearly immediately – the web interface of the device would hang on me after few days of uptime. sometimes it wasn’t even possible to log in, other times – i could log in …

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“operator or administrator has refused the request (0x800710E0)” in the windows task scheduler

at work we have a Windows 2012 server [ more than one. sadly… ]. one of them had few nightly batch jobs started from the task scheduler. a certain task would fail occasionally and give us the “operator or administrator has refused the request (0x800710E0)” error. googling did not help much – it’s a server, …

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tuning spmassasin to treat more harshly mails with forged sender’s address claiming to come from us

once in a while we get e-mails with spoofed sender’s address claiming to come from @ourorg.com. this can fool some of our users; outlook displaying an image of sender solely based on the From: field does not help here. some of those messages have different Return-Path pointing to @someotherscammy.site, other have it also pointing to …

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drac5 / 6 with latest java 1.8.73

new java – new problems. “Error when reading form SSL socket connection” showed again after the upgrade to new java follow the steps from the earlier post and edit those in the C:\Program Files (x86)\Java\jre1.8.0_73\lib\security\java.security: also: go to the Control panel > java in the General tab: Settings > Delete files – mark all the …

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