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diff --git a/man2/syslog.2 b/man2/syslog.2 deleted file mode 100644 index a799c82..0000000 --- a/man2/syslog.2 +++ /dev/null @@ -1,378 +0,0 @@ -'\" t -.\" Copyright (C) 1995 Andries Brouwer (aeb@cwi.nl) -.\" and Copyright (C) 2012, 2014 Michael Kerrisk <mtk.manpages@gmail.com> -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.\" Written 11 June 1995 by Andries Brouwer <aeb@cwi.nl> -.\" 2008-02-15, Jeremy Kerr <jk@ozlabs.org> -.\" Add info on command type 10; add details on types 6, 7, 8, & 9. -.\" 2008-02-15, Michael Kerrisk <mtk.manpages@gmail.com> -.\" Update LOG_BUF_LEN details; update RETURN VALUE section. -.\" -.TH syslog 2 2023-10-31 "Linux man-pages 6.7" -.SH NAME -syslog, klogctl \- read and/or clear kernel message ring buffer; -set console_loglevel -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.BR "#include <sys/klog.h>" " /* Definition of " SYSLOG_* " constants */" -.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */" -.B #include <unistd.h> -.P -.BI "int syscall(SYS_syslog, int " type ", char *" bufp ", int " len ); -.P -/* The glibc interface */ -.B #include <sys/klog.h> -.P -.BI "int klogctl(int " type ", char *" bufp ", int " len ); -.fi -.SH DESCRIPTION -.IR Note : -Probably, you are looking for the C library function -.BR syslog (), -which talks to -.BR syslogd (8); -see -.BR syslog (3) -for details. -.P -This page describes the kernel -.BR syslog () -system call, which is used to control the kernel -.IR printk () -buffer; the glibc wrapper function for the system call is called -.BR klogctl (). -.SS The kernel log buffer -The kernel has a cyclic buffer of length -.B LOG_BUF_LEN -in which messages given as arguments to the kernel function -.BR printk () -are stored (regardless of their log level). -In early kernels, -.B LOG_BUF_LEN -had the value 4096; -from Linux 1.3.54, it was 8192; -from Linux 2.1.113, it was 16384; -since Linux 2.4.23/2.6, the value is a kernel configuration option -.RB ( CONFIG_LOG_BUF_SHIFT , -default value dependent on the architecture). -.\" Under "General setup" ==> "Kernel log buffer size" -.\" For Linux 2.6, precisely the option seems to have appeared in Linux 2.5.55. -Since Linux 2.6.6, the size can be queried with command type 10 (see below). -.SS Commands -The \fItype\fP argument determines the action taken by this function. -The list below specifies the values for -.IR type . -The symbolic names are defined in the kernel source, -but are not exported to user space; -you will either need to use the numbers, or define the names yourself. -.TP -.BR SYSLOG_ACTION_CLOSE " (0)" -Close the log. -Currently a NOP. -.TP -.BR SYSLOG_ACTION_OPEN " (1)" -Open the log. -Currently a NOP. -.TP -.BR SYSLOG_ACTION_READ " (2)" -Read from the log. -The call -waits until the kernel log buffer is nonempty, and then reads -at most \fIlen\fP bytes into the buffer pointed to by -.IR bufp . -The call returns the number of bytes read. -Bytes read from the log disappear from the log buffer: -the information can be read only once. -This is the function executed by the kernel when a user program reads -.IR /proc/kmsg . -.TP -.BR SYSLOG_ACTION_READ_ALL " (3)" -Read all messages remaining in the ring buffer, -placing them in the buffer pointed to by -.IR bufp . -The call reads the last \fIlen\fP -bytes from the log buffer (nondestructively), -but will not read more than was written into the buffer since the -last "clear ring buffer" command (see command 5 below)). -The call returns the number of bytes read. -.TP -.BR SYSLOG_ACTION_READ_CLEAR " (4)" -Read and clear all messages remaining in the ring buffer. -The call does precisely the same as for a -.I type -of 3, but also executes the "clear ring buffer" command. -.TP -.BR SYSLOG_ACTION_CLEAR " (5)" -The call executes just the "clear ring buffer" command. -The -.I bufp -and -.I len -arguments are ignored. -.IP -This command does not really clear the ring buffer. -Rather, it sets a kernel bookkeeping variable that -determines the results returned by commands 3 -.RB ( SYSLOG_ACTION_READ_ALL ) -and 4 -.RB ( SYSLOG_ACTION_READ_CLEAR ). -This command has no effect on commands 2 -.RB ( SYSLOG_ACTION_READ ) -and 9 -.RB ( SYSLOG_ACTION_SIZE_UNREAD ). -.TP -.BR SYSLOG_ACTION_CONSOLE_OFF " (6)" -The command saves the current value of -.I console_loglevel -and then sets -.I console_loglevel -to -.IR minimum_console_loglevel , -so that no messages are printed to the console. -Before Linux 2.6.32, -.\" commit 1aaad49e856ce41adc07d8ae0c8ef35fc4483245 -the command simply sets -.I console_loglevel -to -.IR minimum_console_loglevel . -See the discussion of -.IR /proc/sys/kernel/printk , -below. -.IP -The -.I bufp -and -.I len -arguments are ignored. -.TP -.BR SYSLOG_ACTION_CONSOLE_ON " (7)" -If a previous -.B SYSLOG_ACTION_CONSOLE_OFF -command has been performed, -this command restores -.I console_loglevel -to the value that was saved by that command. -Before Linux 2.6.32, -.\" commit 1aaad49e856ce41adc07d8ae0c8ef35fc4483245 -this command simply sets -.I console_loglevel -to -.IR default_console_loglevel . -See the discussion of -.IR /proc/sys/kernel/printk , -below. -.IP -The -.I bufp -and -.I len -arguments are ignored. -.TP -.BR SYSLOG_ACTION_CONSOLE_LEVEL " (8)" -The call sets -.I console_loglevel -to the value given in -.IR len , -which must be an integer between 1 and 8 (inclusive). -The kernel silently enforces a minimum value of -.I minimum_console_loglevel -for -.IR len . -See the -.I log level -section for details. -The -.I bufp -argument is ignored. -.TP -.BR SYSLOG_ACTION_SIZE_UNREAD " (9) (since Linux 2.4.10)" -The call -returns the number of bytes currently available to be read -from the kernel log buffer via command 2 -.RB ( SYSLOG_ACTION_READ ). -The -.I bufp -and -.I len -arguments are ignored. -.TP -.BR SYSLOG_ACTION_SIZE_BUFFER " (10) (since Linux 2.6.6)" -This command returns the total size of the kernel log buffer. -The -.I bufp -and -.I len -arguments are ignored. -.P -All commands except 3 and 10 require privilege. -In Linux kernels before Linux 2.6.37, -command types 3 and 10 are allowed to unprivileged processes; -since Linux 2.6.37, -these commands are allowed to unprivileged processes only if -.I /proc/sys/kernel/dmesg_restrict -has the value 0. -Before Linux 2.6.37, "privileged" means that the caller has the -.B CAP_SYS_ADMIN -capability. -Since Linux 2.6.37, -"privileged" means that the caller has either the -.B CAP_SYS_ADMIN -capability (now deprecated for this purpose) or the (new) -.B CAP_SYSLOG -capability. -.\" -.\" -.SS /proc/sys/kernel/printk -.I /proc/sys/kernel/printk -is a writable file containing four integer values that influence kernel -.I printk() -behavior when printing or logging error messages. -The four values are: -.TP -.I console_loglevel -Only messages with a log level lower than this value will -be printed to the console. -The default value for this field is -.B DEFAULT_CONSOLE_LOGLEVEL -(7), but it is set to -4 if the kernel command line contains the word "quiet",\" since Linux 2.4 -10 if the kernel command line contains the word "debug", -and to 15 in case -of a kernel fault (the 10 and 15 are just silly, and equivalent to 8). -The value of -.I console_loglevel -can be set (to a value in the range 1\[en]8) by a -.BR syslog () -call with a -.I type -of 8. -.TP -.I default_message_loglevel -This value will be used as the log level for -.I printk() -messages that do not have an explicit level. -Up to and including Linux 2.6.38, -the hard-coded default value for this field was 4 -.RB ( KERN_WARNING ); -since Linux 2.6.39, -.\" commit 5af5bcb8d37f99ba415a1adc6da71051b84f93a5 -the default value is defined by the kernel configuration option -.BR CONFIG_DEFAULT_MESSAGE_LOGLEVEL , -which defaults to 4. -.TP -.I minimum_console_loglevel -The value in this field is the minimum value to which -.I console_loglevel -can be set. -.TP -.I default_console_loglevel -This is the default value for -.IR console_loglevel . -.\" -.\" -.SS The log level -Every -.IR printk () -message has its own log level. -If the log level is not explicitly specified as part of the message, -it defaults to -.IR default_message_loglevel . -The conventional meaning of the log level is as follows: -.TS -lB lB lB -lB c l. -Kernel constant Level value Meaning -KERN_EMERG 0 System is unusable -KERN_ALERT 1 T{ -Action must be taken immediately -T} -KERN_CRIT 2 Critical conditions -KERN_ERR 3 Error conditions -KERN_WARNING 4 Warning conditions -KERN_NOTICE 5 T{ -Normal but significant condition -T} -KERN_INFO 6 Informational -KERN_DEBUG 7 Debug-level messages -.TE -.P -The kernel -.I printk() -routine will print a message on the -console only if it has a log level less than the value of -.IR console_loglevel . -.SH RETURN VALUE -For \fItype\fP equal to 2, 3, or 4, a successful call to -.BR syslog () -returns the number -of bytes read. -For \fItype\fP 9, -.BR syslog () -returns the number of bytes currently -available to be read on the kernel log buffer. -For \fItype\fP 10, -.BR syslog () -returns the total size of the kernel log buffer. -For other values of \fItype\fP, 0 is returned on success. -.P -In case of error, \-1 is returned, -and \fIerrno\fP is set to indicate the error. -.SH ERRORS -.TP -.B EINVAL -Bad arguments (e.g., -bad -.IR type ; -or for -.I type -2, 3, or 4, -.I buf -is NULL, -or -.I len -is less than zero; or for -.I type -8, the -.I level -is outside the range 1 to 8). -.TP -.B ENOSYS -This -.BR syslog () -system call is not available, because the kernel was compiled with the -.B CONFIG_PRINTK -kernel-configuration option disabled. -.TP -.B EPERM -An attempt was made to change -.I console_loglevel -or clear the kernel -message ring buffer by a process without sufficient privilege -(more precisely: without the -.B CAP_SYS_ADMIN -or -.B CAP_SYSLOG -capability). -.TP -.B ERESTARTSYS -System call was interrupted by a signal; nothing was read. -(This can be seen only during a trace.) -.SH STANDARDS -Linux. -.SH HISTORY -From the very start, people noted that it is unfortunate that -a system call and a library routine of the same name are entirely -different animals. -.\" In libc4 and libc5 the number of this call was defined by -.\" .BR SYS_klog . -.\" In glibc 2.0 the syscall is baptized -.\" .BR klogctl (). -.SH SEE ALSO -.BR dmesg (1), -.BR syslog (3), -.BR capabilities (7) |