posts: Add a new article on containers

Signed-off-by: Santosh Sivaraj <santosh@fossix.org>

Author: santoshs

Gemfile

@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-# gem "jekyll", ">= 3.8.3"
+gem "jekyll"
 
 group :jekyll_plugins do
   gem "jekyll-sitemap"
@@ -11,7 +11,7 @@ group :jekyll_plugins do
 end
 
 group :jekyll_plugins do
-  gem "jekyll-feed", "~> 0.6"
+  gem "jekyll-feed"
 end
 
 gem "github-pages", group: :jekyll_plugins

_posts/2018-12-22-haskool.md

@@ -3,7 +3,7 @@ layout: post
 title:  "Haskell functions"
 excerpt: "Haskell learning steps: functions"
 date:   2018-12-23 11:29:17 +0530
-categories: blog
+categories: blogs
 tags: haskell functions
 author: sab
 ---

_posts/2020-10-01-Cointainers.md

@@ -0,0 +1,92 @@
+---
+layout: post
+title:  "Writing containers in Linux"
+excerpt: "Literate programming attempt of writing containers"
+date:   2020-10-01 10:28:45 +0530
+categories: articles
+tags: [linux, containers]
+author: santosh
+---
+
+## Creating Containers
+A basic contianer can be created with minimal amount of code.
+
+### Container
+
+```c
+struct container {
+	char *name;
+	char *rootfs;
+	char *cmd;
+	void *stack;
+};
+
+struct container *new_container(char *name, char *rootfs, char *cmd)
+{
+	struct container *c;
+
+	c = calloc(sizeof(struct container), 1);
+	if (!c)
+		err(errno, "Container");
+
+	c->name = strdup(name);
+	c->rootfs = strdup(rootfs);
+	c->cmd = strdup(cmd);
+
+	if (!c->name || !c->rootfs || !c->cmd)
+		err(errno, "Container");
+
+	return c;
+}
+```
+
+### Cloning Process
+
+Clone process using the \`clone\` system call with the appropriate namespace
+flags to create a new namespace for the contianer.
+
+```c
+#define STACK_SIZE (1024 * 1024)
+
+int run_container(struct container *c)
+{
+	int pid;
+
+	/* We will add the network namespace later */
+	int cloneflags = CLONE_NEWPID|CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC;
+	cloneflags |= SIGCHLD;
+
+	c->stack = malloc(STACK_SIZE);
+	if (!c->stack)
+		err(errno, "Stack creation");
+
+	printf("Cloning\n");
+	pid = clone(_container_exec, c->stack + STACK_SIZE, cloneflags, (void *) c);
+	if (pid == -1)
+		err(errno, "Clone");
+
+	printf("Cloned\n");
+
+	return pid;
+}
+```
+
+### Change root filesystem
+
+```c
+    if (chroot(c->rootfs) == -1)
+            err(errno, "chroot");
+    
+    if (chdir(c->rootfs) == -1)
+            err(errno, "chdir");
+    
+    /* mount proc so we can run `ps` etc */
+    if (mount("proc", "/proc", "proc", 0, NULL) == -1)
+            err(errno, "mount");
+```
+
+<!-- ### Change memory, cpu, network limits using cgroups -->
+
+
+<!-- ### Execute the main container process -->
+