Linux on Council of Elrond

SaltStack_Guide

Tue, 21 Jul 2026 03:00:00 +0800

Target platform: Debian / Ubuntu. Current LTS at time of writing: Salt 3008 LTS. Packages are now hosted on Broadcom’s Artifactory (the old repo.saltproject.io has been retired).

1. What Salt is

Salt (formerly SaltStack) is an open-source automation and infrastructure management framework used for:

Configuration management
Remote command execution
Software deployment
Server orchestration
Compliance enforcement
Infrastructure automation
Network device automation

It runs in two common modes:

Master / minion (agent) mode — a central salt-master sends commands to many salt-minion agents over an encrypted ZeroMQ message bus. This is the classic, scalable setup:

Perftest_RDMA_Benchmarking

Sat, 18 Jul 2026 20:00:00 +0800

What is perftest?

perftest is the standard micro-benchmark suite for RDMA — it validates and benchmarks InfiniBand, hardware RoCE, and Soft-RoCE links, not ordinary TCP networking. Each tool measures one RDMA verb:

Test	Measures	Real-world workloads it models
`ib_write_bw`	RDMA Write bandwidth	Data replication, storage writes, GPU/bulk data transfers
`ib_write_lat`	RDMA Write latency	Updating remote memory — small one-sided writes
`ib_read_bw`	RDMA Read bandwidth	Distributed storage and database reads, remote memory access
`ib_read_lat`	RDMA Read latency	Fetching remote memory — storage/database-style lookups
`ib_send_bw`	Send/Receive bandwidth	MPI messages, RPC, request queues
`ib_send_lat`	Send/Receive latency	Small request/response round trips — RPC and MPI latency
`ib_atomic_bw`	Atomic operation rate	Distributed locks and counters
`ib_atomic_lat`	Atomic latency	Synchronization primitives

Write, Read, and Send are different operations

The grouping in the table is not accidental — the three verbs have different semantics:

How_Linux_Sends_and_Receives_Network_Packets

Sat, 11 Jul 2026 07:00:00 +0800

Study notes rewritten in my own words

Network models

To let all kinds of devices talk to each other over a network, the ISO defined the OSI reference model with 7 layers. Each layer has a single job:

Application – provides a uniform interface to programs
Presentation – converts data into a format another system understands
Session – establishes, manages and terminates sessions
Transport – end-to-end data transfer
Network – routing, forwarding, fragmentation
Data link – framing, error detection, MAC addressing
Physical – transmits frames over the physical medium

OSI is mostly a conceptual model — it never shipped a concrete implementation. What we actually use is the simpler TCP/IP model with 4 layers, and the Linux stack is built to match it:

Mysql_installation

Sun, 07 Feb 2021 18:33:58 +0800

The general view of the difference between mysql and marinaDB can refer to this link:

https://blog.panoply.io/a-comparative-vmariadb-vs-mysql

And I quote some here:

MySQL: MySQL is an open-source relational database management system (RDBMS). Just like all other relational databases, MySQL uses tables, constraints, triggers, roles, stored procedures and views as the core components that you work with. A table consists of rows, and each row contains a same set of columns. MySQL uses primary keys to uniquely identify each row (a.k.a record) in a table, and foreign keys to assure the referential integrity between two related tables.

Linux_name_space

Fri, 01 Jan 2021 14:52:01 +0800

Linux NameSpace

Docker denpends on Linux NameSpace, Thus this is a brief explaination on linux name space.

We can use unshare command to manipulate/playaround with linux name spaces.

How to check what kind of linux namespace is supported

We can use “man unshare” to check what kind of linux namespace is supported. There are 8 types of name spaces:

 mount namespace
 Mounting and unmounting filesystems will not affect the rest of the system (CLONE_NEWNS flag), except for filesystems which are explicitly marked as shared (with mount --make-shared; see /proc/self/mountinfo or
 findmnt -o+PROPAGATION for the shared flags).

 unshare automatically sets propagation to private in the new mount namespace to make sure that the new namespace is really unshared. This feature is possible to disable by option --propagation unchanged. Note
 that private is the kernel default.

 UTS namespace
 Setting hostname or domainname will not affect the rest of the system. (CLONE_NEWUTS flag)

 IPC namespace
 The process will have an independent namespace for System V message queues, semaphore sets and shared memory segments. (CLONE_NEWIPC flag)

 network namespace
 The process will have independent IPv4 and IPv6 stacks, IP routing tables, firewall rules, the /proc/net and /sys/class/net directory trees, sockets, etc. (CLONE_NEWNET flag)

 pid namespace
 Children will have a distinct set of PID to process mappings from their parent. (CLONE_NEWPID flag)

 user namespace
 The process will have a distinct set of UIDs, GIDs and capabilities. (CLONE_NEWUSER flag)

 See clone(2) for the exact semantics of the flags.

Mount（mnt） isolate mounting space
Process ID (pid) isolate process ID.
Network (net) isolate network , port ID, etc
Interprocess Communication (ipc) isolate System V IPC & POSIX message queues
UTS Namespace(uts) Isolate hostname and domain name
User Namespace (user) isolate user group and users.

Additionally, Linux 4.6 and 5.6 introduced cgroups and time two types. in total it’s 8.

squid_setup

Thu, 18 Jun 2020 23:15:45 +0800

1. yum -y update

2. yum install openssl

3. yum install squid

4. vim /etc/squid/squid.conf

5. tail -f /var/log/squid/access.log

6. systemctl start squid

7. systemctl status squid

8. ss -nlp | grep squid | grep 3128

dns_nameservers 8.8.8.8 8.8.4.4