eolas/Linux/journald.md

---
categories:
  - Linux
tags: [systems-programming]
---

# `journald`

`journald` is a program that comes as default with [systemd](/Linux/systemd.md). It is a service fror collecting and storing system-level log data. I keeps a track of all [kernel](/Operating_Systems/The_Kernel.md) processes. It is invaluable when tracing the source of problems and errors that may arise on the system level. It keeps a track of all kernal processes.

![](/_img/journald.png)

## `journalctl`

We use `journalctl` to access the logs. The command by itself outputs the entire log which will be huge and hard to scroll through. We can refine the results with modifiers.

### View logs for a specific process with pid

```bash
journalctl _PID=1234
```

### View logs for a specific time period

This can be really helpful since you can bracket the most recent events which will be more memorable.

```bash
journalctl -S -1h
```

### View logs for a specfic systemd unit

```bash
journalctl -u [unit_name] -e
```

### View boot logs

```bash
journalctl -b
```

#### Identify specific boot

```bash
journalctl --list-boots

```

### List only kernel entries to the journal

```bash
journalctl -k

```