# System Log

## Viewing the system log from LuCi

Select the `Status >> System Log` menu entry.

![alt text](images/librecmc-luci-selecting-system-log.png "Selecting
 the System Log page in LuCi")

![alt text](images/librecmc-luci-system-log.png "The System Log page
 in LuCi")

The `System Log` page in LuCi does not have an interface for filtering
output. Therefore, you will likely want to use the shell interface.

## Viewing the system log from the shell

Once logged in via SSH, use the `logread` command

```bash
Usage: logread [options]
Options:
    -s <path>		Path to ubus socket
    -l	<count>		Got only the last 'count' messages
    -e	<pattern>	Filter messages with a regexp
    -r	<server> <port>	Stream message to a server
    -F	<file>		Log file
    -S	<bytes>		Log size
    -p	<file>		PID file
    -h	<hostname>	Add hostname to the message
    -P	<prefix>	Prefix custom text to streamed messages
    -f			Follow log messages
    -u			Use UDP as the protocol
    -t			Add an extra timestamp
    -0			Use \0 instead of \n as trailer when using TCP
```

For example:

```bash
root@libreCMC:~$ logread | grep 'kern\.warn'
Mon Jan 15 20:22:01 2018 kern.warn kernel: [    0.000000] No valid device tree found, continuing without
Mon Jan 15 20:22:01 2018 kern.warn kernel: [    0.000000] Primary instruction cache 64kB, VIPT, 4-way, linesize 32 bytes.
Mon Jan 15 20:22:01 2018 kern.warn kernel: [    0.000000] Primary data cache 32kB, 4-way, VIPT, cache aliases, linesize 32 bytes
Mon Jan 15 20:22:01 2018 kern.warn kernel: [    0.669305] Crashlog allocated RAM at address 0x3f00000
Mon Jan 15 20:22:01 2018 kern.warn kernel: [    0.752178] m25p80 spi0.0: found mx25l12805d, expected m25p80
```

One should be able to use `logread -e` instead of `grep`, but it seems
that not all the same regular expressions work for both:

```bash
root@libreCMC:~$ logread -e 'kern\.warn' # and other similar variations
(no output)
```

The system log is contained in a limited size, circular buffer in
memory. So, if you have some process writing messages periodically,
this will eventually erase messages that were only written once.

## Configuring the system log

TODO

## Monitoring the system log

TODO