open-nomad/website/content/docs/commands/alloc/logs.mdx
James Rasell cb6ba80f0f
cli: stream both stdout and stderr when following an alloc. (#16556)
This update changes the behaviour when following logs from an
allocation, so that both stdout and stderr files streamed when the
operator supplies the follow flag. The previous behaviour is held
when all other flags and situations are provided.

Co-authored-by: Luiz Aoqui <luiz@hashicorp.com>
2023-04-04 10:42:27 +01:00

122 lines
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---
layout: docs
page_title: 'Commands: alloc logs'
description: |
Stream the logs of a task.
---
# Command: alloc logs
**Alias: `nomad logs`**
The `alloc logs` command displays the log of a given task.
## Usage
```plaintext
nomad alloc logs [options] <allocation> <task>
```
This command streams the logs of the given task in the allocation. If the
allocation is only running a single task, the task name can be omitted.
Optionally, the `-job` option may be used in which case a random allocation from
the given job will be chosen.
Task name may also be specified using the `-task` option rather than a command
argument. If task name is given with both an argument and the `-task` option,
preference is given to the `-task` option.
When ACLs are enabled, this command requires a token with the `read-logs`,
`read-job`, and `list-jobs` capabilities for the allocation's namespace.
## General Options
@include 'general_options.mdx'
## Logs Options
- `-stdout`: Display stdout logs. This is used as the default value in all
commands except when using the `-f` flag where both stdout and stderr are
used as default.
- `-stderr`: Display stderr logs.
- `-verbose`: Display verbose output.
- `-job`: Use a random allocation from the specified job, preferring a running
allocation.
- `-task`: Specify the task to view the logs.
- `-f`: Causes the output to not stop when the end of the logs are reached, but
rather to wait for additional output. When supplied with no other flags except
optionally `-job` and `-task`, both stdout and stderr logs will be followed.
- `-tail`: Show the logs contents with offsets relative to the end of the logs.
If no offset is given, -n is defaulted to 10.
- `-n`: Sets the tail location in best-efforted number of lines relative to the
end of the logs.
- `-c`: Sets the tail location in number of bytes relative to the end of the
logs.
Note that the `-no-color` option applies to Nomad's own output. If the task's
logs include terminal escape sequences for color codes, Nomad will not remove
them.
## Examples
```shell-session
$ nomad alloc logs eb17e557 redis
foobar
baz
bam
$ nomad alloc logs -stderr eb17e557 redis
[ERR]: foo
[ERR]: bar
$ nomad alloc logs -job example
[ERR]: foo
[ERR]: bar
$ nomad alloc logs -tail -n 2 eb17e557 redis
foobar
baz
$ nomad alloc logs -tail -f -n 3 eb17e557 redis
foobar
baz
bam
<blocking>
```
Specifying task name with the `-task` option:
```shell-session
$ nomad alloc logs -task redis eb17e557
```
If task name is specified using both options, the command argument is ignored.
The following will output the logs from the "redis" task only, not the "api" task:
```shell-session
$ nomad alloc logs -task redis eb17e557 api
```
## Using Job ID instead of Allocation ID
Setting the `-job` flag causes a random allocation of the specified job to be
selected. Nomad will prefer to select a running allocation ID for the job, but
if no running allocations for the job are found, Nomad will use a dead
allocation.
```plaintext
nomad alloc logs -job <job-id> <task>
```
Choosing a specific allocation is useful for debugging issues with a specific
instance of a service. For other operations using the `-job` flag may be more
convenient than looking up an allocation ID to use.