From 5756a30690bf66a70710e2155bcff333721fdb67 Mon Sep 17 00:00:00 2001
From: Jet Hughes <jethughes0@gmail.com>
Date: Tue, 28 Mar 2023 15:21:29 +1300
Subject: [PATCH] vault backup: 2023-03-28 15:21:29

---
 content/notes/10-scheduled-tasks-and-logs.md | 69 ++++++++++++++++++--
 1 file changed, 64 insertions(+), 5 deletions(-)

diff --git a/content/notes/10-scheduled-tasks-and-logs.md b/content/notes/10-scheduled-tasks-and-logs.md
index b2cabe2e8..078031639 100644
--- a/content/notes/10-scheduled-tasks-and-logs.md
+++ b/content/notes/10-scheduled-tasks-and-logs.md
@@ -5,7 +5,7 @@ tags:
 - cosc301
 ---
 
-Daemon 
+DAEMON 
 - A process that runs in the background and is independent of control from all terminals 
 - Reasons for daemons’ independence of terminals 
 	- Prevent daemons’ error message from appearing on a user’s terminal 
@@ -13,7 +13,7 @@ Daemon
 - Typical daemons 
 	- crond, syslogd
 
-Daemonization
+DAEMONIZATION
 ```
 if( (pid = fork()) != 0) exit(0); //parent terminates 
 setsid(); // become session leader 
@@ -23,9 +23,10 @@ signal(SIGHUP, SIG_IGN); if( (pid = fork()) != 0) exit(0); //new child continues
 
 The purpose is to make the process independent of the control from any terminals.
 
-> [!INFO] when you are independent from 
+> [!INFO] when you are independent from parent you are a leader.
+> need to ignore sighup signal otherwise child would be automatically terminated when the parent is killed.
 
-Scheduled tasks 
+SCHEDULED TASKS
 - Automating tasks 
 	- crond and crontab 
 	- crond is a very important daemon for automatically executing tasks 
@@ -34,4 +35,62 @@ Scheduled tasks
 	- Clean file systems 
 	- Log rotate 
 	- Check log files 
-	- Monitor system status and resources
\ No newline at end of file
+	- Monitor system status and resources
+> [!INFO] can run any command/script on a schedule
+> for security you should scan logs everyday to check for keywords
+> useing grep, sed, awk
+
+SYSLOGD 
+- How it works? 
+	- Read the configuration file /etc/syslog.conf 
+	- A Unix domain socket is created and bound to the pathname /var/run/log 
+	- A UDP socket is created and bound to port 514 
+	- Runs in an infinite loop that calls select, waiting for any one of the above descriptors to be readable, reads the log message, and does what the configuration file says to do with that message. 
+	- If the daemon receives the SIGHUP signal, it rereads the configuration file
+> [!INFO] syslogd is a daemon. 
+
+LOGGING FUNCTIONS
+- How start and close logging? 
+	- Create a Unix domain datagram socket and send out messages to the pathname the daemon has bound, or send them to port 514 by a UDP socket 
+	- openlog() and closelog() 
+- How to send log messages 
+	- void syslog(int priority, const char *message, …); 
+	- priority is a combination of a level and a facility shown later 
+	- message is like a format string to printf, with the addition of a %m specification, which is replaced with the error message corresponding to the current value of errno.
+> [!INFO] some log messages go to other locations
+
+Example code 
+- openlog ("mylibrary", option, priority); 
+- syslog (LOG_INFO, “My library has been invoked”); 
+- closelog ();
+
+Level 
+- LOG_EMERG (0): system is unusable 
+- LOG_ALERT (1): action must be taken immediately 
+- LOG_CRIT (2): critical conditions 
+- LOG_ERR (3): error conditions 
+- LOG_WARNING (4): warning conditions 
+- LOG_NOTICE (5): normal but significant conditions 
+- LOG_INFO (6): informational 
+- LOG_DEBUG (7): debug-level messages, has lowest priority
+
+Facility 
+- Identify the type of process sending the message 
+- Facilities 
+	- LOG_AUTH: security/authorization messages 
+	- LOG_AUTHPRIV: security/authorization messages (private) 
+	- LOG_CRON: from crond 
+	- LOG_KERN: kernel messages 
+	- LOG_MAIL: mail system 
+	- LOG_USER: random user-level messages (default) 
+	- LOG_FTP: from ftpd 
+	- LOG_LPR: line printer system 
+	- LOG_SYSLOG: internal messages from syslogd 
+	- LOG_LOCAL0 
+	- LOG_LOCAL7: local, discretional use by programmers.
+
+klogd 
+- klogd provides a facility for system admin to check only kernel messages (which can also be checked through syslogd) 
+- Kernel messages can be read from /proc/kmsg 
+- Use /proc/sys/kernel/printk to control the level of log messages. 
+	- cat /proc/sys/kernel/printk
\ No newline at end of file