I started playing with Docker and here I will write some commands that where not so obvious at beginning 😃 List running containers: docker ps List also not running containers: docker ps -a Remove all containers (be careful with that): docker rm $(docker ps -a -q) Remove all images: docker rmi $(docker images -q) Docker won’t remove any old volumes used by containers, so after some time you may be interested in deleting them all: ...

I was doing a lot of changes to my old posts, switched to HTTPS, etc. Sometimes it was useful to change some particular text in all my old posts at a time, but there is no such feature in WordPress. But WordPress runs on MySQL and I could use SQL query to update such posts. Make backup - it’s not required but strongly advised 😃 Now use this query as template to replace in place whatever you need: UPDATE wp_posts SET post_content = REPLACE(post_content, " ", ""); You should see something like: ...

From few days I have access to UPC’s www.horizon.tv  external link platform - until now it was useless on Linux. But there is Pipelight that will use Wine to emulate Silverlight on Linux and it’s working pretty well - you’re just few commands away from achieving that: # stop browser killall firefox # remove old version if you have it sudo apt-get remove pipelight Now configure repos and install packages: ...

I just bought new wifi card for my desktop computer. Like in topic, it’s Intel Dual Band Wireless-AC 7260 for Desktop  external link . I was searching for card that: support AC standard have 5GHz network support (2,4GHz channels are cluttered heavily in my neighborhood have PCI/PCIx or USB3 connector is Linux friendly (no modules compilation by hand, support for aircrack-ng, kismet) This one is the only I found that comply my expectations. ...

I watched nice presentation about how Cloudflare protects itself against DoS. Most of us are not able to do that exactly like them but some of tips were general enough to be used on typical web front server. I took notes from this presentation and presented here. Thanks to Marek agreement I also reposted all examples (in easier to copy paste way). Howto prepare against ACK/FIN/RST/X-mas flood Use conntrack rule: ...

I was looking at backup task running on my desk and saw that it’s spending a lot of time on ~/.local/share/zeitgeist directory. I checked and it had 4.6GB: du -sh ~/.local/share/zeitgeist/* 118M activity.sqlite 44M activity.sqlite.bck 32K activity.sqlite-shm 4,4G activity.sqlite-wal 311M fts.index WTF? Fortunately I found here  external link that I could easily delete some of this: zeitgeist-daemon --quit Now check that it’s not running: ...

There are many possible real life cases and not all optimization technics will be suitable for you but I hope it will be a good starting place. Also you shouldn’t copy paste examples with faith that they will make your server fly 😃 You have to support your decisions with excessive tests and help of monitoring system (ex. Grafana ). Cache static and dynamic content Setting caching static and dynamic content strategy may offload your server from additional load from repetitive downloads of same, rarely updated files. This will make your site to load faster for frequent visitors. ...

Sometime you need to make quick and dirty image backup of VM running on XenServer and this post is about such case 😃 List machines: xl list Name ID Mem VCPUs State Time(s) Domain-0 0 4066 8 r----- 3526567.3 webfront1.example.com 1 4096 4 r----- 3186487.2 webfront2.example.com 2 2048 2 -b---- 920408.2 Now you may export one: xe vm-export vm=webfront1.example.com filename=/srv/backup/webfront.xva Export succeeded You may also use uuid for that - list machines with xe vm-list (best with less) and then: ...

Sometimes deployment process or other heavy task may cause some Nagios checks to rise below normal levels and bother admin1. If this is expected and you want to add downtime on host/service during this task you may use this script: #!/bin/bash function die { echo $1; exit 1; } if [[ $# -eq 0 ]] ; then die "Give hostname and time in minutes as parameter!" fi if [[ $# -eq 1 ]] ; then MINUTES=15 else MINUTES=$2 fi HOST=$1 NAGURL=http://nagios.example.com/nagios/cgi-bin/cmd.cgi USER=nagiosuser PASS=nagiospassword SERVICENAME=someservice COMMENT="Deploying new code" export MINUTES echo "Scheduling downtime on $HOST for $MINUTES minutes..." # The following is urlencoded already STARTDATE=`date "+%d-%m-%Y %H:%M:%S"` # This gives us the date/time X minutes from now ENDDATE=`date "+%d-%m-%Y %H:%M:%S" -d "$MINUTES min"` curl --silent --show-error \ --data cmd_typ=56 \ --data cmd_mod=2 \ --data host=$HOST \ --data-urlencode "service=$SERVICENAME" \ --data-urlencode "com_data=$COMMENT" \ --data trigger=0 \ --data-urlencode "start_time=$STARTDATE" \ --data-urlencode "end_time=$ENDDATE" \ --data fixed=1 \ --data hours=2 \ --data minutes=0 \ --data btnSubmit=Commit \ --insecure \ $NAGURL -u "$USER:$PASS"| grep -q "Your command request was successfully submitted to Nagios for processing." || die "Failed to con tact nagios"; echo Scheduled downtime on nagios from $STARTDATE to $ENDDATE Threat this script as template with some tips: ...

Now when you have CollectD and InfluxDB installed you may configure Grafana 😃 First configure repo with current Grafana version (select your distro): curl https://packagecloud.io/gpg.key | sudo apt-key add - deb https://packagecloud.io/grafana/testing/debian/ wheezy main Now install package (on wheezy I needed to install apt-transport-https to allow installation of packages from repo via HTTPS): apt-get update apt-get install -y apt-transport-https apt-get install -y grafana By default Grafana will use sqlite database to keep information about users, etc: ...