This is a quick guide to mounting a qcow2 disk images on your host server. This is useful to reset passwords, edit files, or recover something without the virtual machine running.
Step 1 - Enable NBD on the Host
modprobe nbd max_part=8
Eric Wolf typetetris
jboner
/ latency.txt
Last active
January 12, 2026 20:16
Latency Numbers Every Programmer Should Know
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Latency Comparison Numbers (~2012) | |
| ---------------------------------- | |
| L1 cache reference 0.5 ns | |
| Branch mispredict 5 ns | |
| L2 cache reference 7 ns 14x L1 cache | |
| Mutex lock/unlock 25 ns | |
| Main memory reference 100 ns 20x L2 cache, 200x L1 cache | |
| Compress 1K bytes with Zippy 3,000 ns 3 us | |
| Send 1K bytes over 1 Gbps network 10,000 ns 10 us | |
| Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD |
jFransham
/ Rust Optimization.md
Last active
December 25, 2025 23:55
pinkeen
/ DOCKER_SYSTEMD_CGROUPV2.md
Last active
July 13, 2025 16:16
Run a systemd container using cgroupv2
In theory this would allow the nested systemd init to manage its own resources via slices and scopes - kind of like with LXC's nested mode but without the nasty security implication of bind mounting the real cgroupfs into the container.
Running a systemd container is not the only thing that this would enable - together with fuse-overlayfs it might allow one to run containers inside containers more securely.
The problem is that by default the nested group is mounted ro into the container which should not be necessary according to my research. It gets mounted rw as expected when userns-remap is enabled in Docker what is not desirable for me. I am not sure if docker/moby/containerd is at fault here or if it's a limitation of Linux control groups or user namespaces. It would be great if som