Linux Tutorials (8) -Linux in the process and the log
Process in Linux
process: start strength has run executable program
1, PID: ID process (each new process has a unique PID)
2, PPID: parent process ID
3, any process can create a child process
4, more than redhat 7, the parent of all processes : systemd
in redhat 5,6, the parent of all processes: init
ps displays the current status of the process
commonly used options
-aux: list all processes
-ef: list all processes
-l: List the current users and related processes
-u user: a user to view the process status
top can view real-time process status
Operation:
R: The process is running or waiting to run
sleep:
S: is sleeping but can be woken
D: is sleeping, and not wake up, the process is interrupted, may cause an abnormal state of the device
K: is sleeping and it can not be awakened, the process can be interrupted.
Stopped:
T: the process is stopped, but can be recovered by other processes
T: being debugged process
zombie:
the Z-: child process send a signal to the parent process when you exit, in addition to PID, all resources released
X: Get the parent structure of the sub-process, sub-process can be completely released, the state of the process is not visible to
the process priority
1, <high priority
2, n low priority? 3, s subprocess comprising? 4 + in the background process group
ps -aux of parameters
1,% CPU: CPU utilization occupancy 2,% MEM:? occupied by the memory usage of 3, VSZ:? occupied by the virtual memory size 4, RSS:? occupied memory size 5? , TTY: secondary device number (minor device number of tty) 6 , STAT terminal:? stroke state of the
instruction being executed: 7, sTART: start time of travel 8, tIME:? execution time 9, cOMMAND?
Linux interrupt process
signals: the process is passed to the Linux operating
kill -l displays all signals can be passed to the Linux process
常用：
kill -9 PID 杀死一个进程—强制
kill -15 PID 正常的方式终止一个进程
kill -2 可以control+c的操作是一样的
start：在系统中启动一项服务
stop：等待程序需处理完毕后再stop，
restart：直接关闭程序 在开启
reload：重新加载配置文件，进程暂停，然后把配置文件加载进去后，继续执行后续操作。进程的PID不会发生改变
enable：设置开机自启
disable：关闭开机自启
status：查看某一单元的状态
Linux in the log
analysis and storage of logs
logs: a system for auditing and troubleshooting -Liunx the "black box"
log files are stored in / var / log directory
in RedHat 7, the system log messages the responsibility of the two services deal with. They are systemd-journald and rsyslogd.
/ var / log / messages // log majority system log messages of
/ var / log / secure // security and authentication of messages and error log
/ var / log / maillog // associated with the mail server's log
/ var / log / cron // log files associated with recurring tasks
/ var / log / boot / log // record a log related to system startup and
most log consists of four parts
1, at the time of recording the log
2 transmits the log the host
3 transmits the log messages or process
4, the actual message sent
Log Monitoring
tail -f / var / log / secure // display the last 10 lines, if there is new content is added, it will continue to output