# Time Namespace
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## Basic Information
The time namespace in Linux allows for per-namespace offsets to the system monotonic and boot-time clocks. It is commonly used in Linux containers to change the date/time within a container and adjust clocks after restoring from a checkpoint or snapshot.
## Lab:
### Create different Namespaces
#### CLI
```bash
sudo unshare -T [--mount-proc] /bin/bash
```
By mounting a new instance of the `/proc` filesystem if you use the param `--mount-proc`, you ensure that the new mount namespace has an **accurate and isolated view of the process information specific to that namespace**.
Error: bash: fork: Cannot allocate memory
When `unshare` is executed without the `-f` option, an error is encountered due to the way Linux handles new PID (Process ID) namespaces. The key details and the solution are outlined below:
1. **Problem Explanation**:
- The Linux kernel allows a process to create new namespaces using the `unshare` system call. However, the process that initiates the creation of a new PID namespace (referred to as the "unshare" process) does not enter the new namespace; only its child processes do.
- Running `%unshare -p /bin/bash%` starts `/bin/bash` in the same process as `unshare`. Consequently, `/bin/bash` and its child processes are in the original PID namespace.
- The first child process of `/bin/bash` in the new namespace becomes PID 1. When this process exits, it triggers the cleanup of the namespace if there are no other processes, as PID 1 has the special role of adopting orphan processes. The Linux kernel will then disable PID allocation in that namespace.
2. **Consequence**:
- The exit of PID 1 in a new namespace leads to the cleaning of the `PIDNS_HASH_ADDING` flag. This results in the `alloc_pid` function failing to allocate a new PID when creating a new process, producing the "Cannot allocate memory" error.
3. **Solution**:
- The issue can be resolved by using the `-f` option with `unshare`. This option makes `unshare` fork a new process after creating the new PID namespace.
- Executing `%unshare -fp /bin/bash%` ensures that the `unshare` command itself becomes PID 1 in the new namespace. `/bin/bash` and its child processes are then safely contained within this new namespace, preventing the premature exit of PID 1 and allowing normal PID allocation.
By ensuring that `unshare` runs with the `-f` flag, the new PID namespace is correctly maintained, allowing `/bin/bash` and its sub-processes to operate without encountering the memory allocation error.
#### Docker
```bash
docker run -ti --name ubuntu1 -v /usr:/ubuntu1 ubuntu bash
```
### Check which namespace is your process in
```bash
ls -l /proc/self/ns/time
lrwxrwxrwx 1 root root 0 Apr 4 21:16 /proc/self/ns/time -> 'time:[4026531834]'
```
### Find all Time namespaces
{% code overflow="wrap" %}
```bash
sudo find /proc -maxdepth 3 -type l -name time -exec readlink {} \; 2>/dev/null | sort -u
# Find the processes with an specific namespace
sudo find /proc -maxdepth 3 -type l -name time -exec ls -l {} \; 2>/dev/null | grep
```
{% endcode %}
### Enter inside a Time namespace
```bash
nsenter -T TARGET_PID --pid /bin/bash
```
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Learn & practice AWS Hacking:[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\
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Support HackTricks
* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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{% endhint %}hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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