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klogd.8: Remove wording on role and superiority over syslogd

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For most use-cases a kernel with CONFIG_KALLSYMS and a stand-alone
syslogd is sufficient.  No need for the complexity of klogd.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
This commit is contained in:
Joachim Nilsson 2019-11-15 09:59:18 +01:00
parent 49968d977e
commit ac8b8ebf0d
1 changed files with 32 additions and 18 deletions
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50
man/klogd.8
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@ -61,19 +61,35 @@ When symbols are expanded, print the line twice. Once with addresses
converted to symbols, once with the raw text. This allows external converted to symbols, once with the raw text. This allows external
programs such as ksymoops do their own processing on the original data. programs such as ksymoops do their own processing on the original data.
.Sh OVERVIEW .Sh OVERVIEW
The functionality of klogd has been typically incorporated into other The basic functionality of klogd is typically included in
versions of syslogd but this seems to be a poor place for it. In the .Nm syslogd .
modern Linux kernel a number of kernel messaging issues such as In a modern Linux kernel a number of kernel messaging issues such as
sourcing, prioritization and resolution of kernel addresses must be sourcing, prioritization and resolution of kernel addresses must be
addressed. Incorporating kernel logging into a separate process offers addressed. This task was previously the role of
a cleaner separation of services. .Nm ,
but with the addition of features like
.Ql CONFIG_KALLSYSMS
the need for a separate
.Nm
has been greatly reduced, so the
.Nm sysklogd
project have disabled
.Nm
by default.
.Pp .Pp
In Linux there are two potential sources of kernel log information: the In Linux there are two potential sources of kernel log information: the
.Pa /proc .Pa /proc
file system and the syscall, file system, specifically the file
.Pa /proc/kmsg ,
and the syscall,
.Fn sys_syslog .Fn sys_syslog
interface, although ultimately interface, see
they are one and the same. .Xr syslog 2
for details, although ultimately they are one and the same.
.Nm syslogd
reads from
.Pa /proc/kmsg ,
but
.Nm .Nm
is designed to choose whichever source of information is the most is designed to choose whichever source of information is the most
appropriate. It does this by first checking for the presence of a appropriate. It does this by first checking for the presence of a
@ -90,13 +106,7 @@ can be used to force
.Nm .Nm
to use the system call interface as its messaging source. to use the system call interface as its messaging source.
.Pp .Pp
If kernel messages are directed through the The raw kernel messages are of the form:
.Nm syslogd
daemon,
.Nm ,
as of version 1.1, has the ability to properly prioritize kernel
messages. Prioritization of kernel log messages was added around Linux
version 0.99pl13. The raw kernel messages are of the form:
.Bd -literal -offset indent .Bd -literal -offset indent
<[0-7]>Something said by the kernel. <[0-7]>Something said by the kernel.
.Ed .Ed
@ -105,9 +115,13 @@ The priority of the kernel message is encoded as a single numeric
digit enclosed inside the digit enclosed inside the
.Ql <> .Ql <>
pair. The definitions of these values is given in the kernel include pair. The definitions of these values is given in the kernel include
file kernel.h. When a message is received from the kernel the klogd file kernel.h. When a message is received from the kernel, by either
daemon reads this priority level and assigns the appropriate priority .Nm syslogd
level to the syslog message. If file output, or
.Nm klogd ,
the daemon reads this priority value and assigns the appropriate
priority level and kernel facility to the syslog message. If file
output,
.Fl f Ar FILE , .Fl f Ar FILE ,
is used the prioritization sequence is left pre-pended to the kernel is used the prioritization sequence is left pre-pended to the kernel
message. message.