Where is the pid file stored in HDFS
Editor to share with you where the pid file in HDFS is stored, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!
1. The pid file is stored in the / tmp directory by default, and the content of the pid file is the process number
[hadoop@hadoop002 ~] $cd / tmp
[hadoop@hadoop002 tmp] $pwd
/ tmp
[hadoop@hadoop002 tmp] $ll
Total 132
Drwxrwxr-x. 4 hadoop hadoop 4096 May 22 12:46 hadoop-hadoop
-rw-rw-r--. 1 hadoop hadoop 5 May 23 11:00 hadoop-hadoop-datanode.pid
-rw-rw-r--. 1 hadoop hadoop 5 May 23 11:00 hadoop-hadoop-namenode.pid
-rw-rw-r--. 1 hadoop hadoop 5 May 23 11:00 hadoop-hadoop-secondarynamenode.pid
Drwxr-xr-x. 2 hadoop hadoop 4096 May 23 13:17 hsperfdata_hadoop
Drwxrwxr-x. 3 hadoop hadoop 4096 May 23 11:00 Jetty_0_0_0_0_50070_hdfs____w2cu08
Drwxrwxr-x. 4 hadoop hadoop 4096 May 23 11:05 Jetty_0_0_0_0_8042_node____19tj0x
Drwxrwxr-x. 3 hadoop hadoop 4096 May 23 11:01 Jetty_hadoop002_50090_secondary____.xoi5bj
Drwxrwxr-x. 4 hadoop hadoop 4096 May 23 11:05 Jetty_hadoop002_8088_cluster____jy43fd
Drwxrwxr-x. 3 hadoop hadoop 4096 May 22 12:43 Jetty_localhost_33164_datanode____.86mfre
Drwxrwxr-x. 3 hadoop hadoop 4096 May 21 16:31 Jetty_localhost_34452_datanode____57ccs7
Drwxrwxr-x. 3 hadoop hadoop 4096 May 22 13:28 Jetty_localhost_35801_datanode____1320ou
Drwxrwxr-x. 3 hadoop hadoop 4096 May 22 11:14 Jetty_localhost_41633_datanode____.reuty8
Drwxrwxr-x. 3 hadoop hadoop 4096 May 21 17:17 Jetty_localhost_43514_datanode____do382o
Drwxrwxr-x. 3 hadoop hadoop 4096 May 23 11:00 Jetty_localhost_54437_datanode____.slqxa8
Drwxrwxr-x. 3 hadoop hadoop 4096 May 22 12:24 Jetty_localhost_55741_datanode____.cj1ayt
Drwxrwxr-x. 3 hadoop hadoop 4096 May 22 12:18 Jetty_localhost_55901_datanode____.91pz3
Drwxrwxr-x. 3 hadoop hadoop 4096 May 22 13:36 Jetty_localhost_59457_datanode____.gif7tz
Drwxrwxr-x. 3 hadoop hadoop 4096 May 22 11:28 Jetty_localhost_59865_datanode____dj2ere
Drwx-. 2 root root 4096 May 23 10:55 keyring-dOEsWO
Drwx-. 2 root root 4096 Apr 21 02:20 keyring-fR5f6f
Drwx-. 2 root root 4096 Apr 21 02:13 keyring-jZCkKD
Drwx-. 2 root root 4096 Apr 20 20:07 keyring-RWPvsu
Drwx-. 2 root root 4096 May 21 16:18 keyring-Rythlk
Drwx-. 2 root root 4096 Apr 25 14:13 keyring-zrMZWC
Srwxrwxrwx. 1 mysql mysql 0 Apr 25 14:17 mysql.sock
Drwx-. 2 gdm gdm 4096 May 23 10:55 orbit-gdm
Drwx-. 2 root root 4096 May 23 10:56 orbit-root
Drwx-. 2 gdm gdm 4096 May 23 10:56 pulse-aQWRK1os9K8n
Drwx-. 2 root root 4096 May 23 10:55 pulse-Zd56fb7r0ESa
Drwx-. 2 root root 4096 May 23 10:55 virtual-root.OV7MJo
Drwx-. 2 root root 4096 May 21 16:18 virtual-root.q1Shey
-rw-rw-r--. 1 hadoop hadoop 5 May 23 11:05 yarn-hadoop-nodemanager.pid
-rw-rw-r--. 1 hadoop hadoop 5 May 23 11:05 yarn-hadoop-resourcemanager.pid
[hadoop@hadoop002 tmp] $
[hadoop@hadoop002 tmp] $cat hadoop-hadoop-datanode.pid
2619
[hadoop@hadoop002 tmp] $
two。 Modify the path of the HADOOP_PID_DIR file
Normally, pid files cannot be placed in the / tmp directory in production, because the pid files under / tmp are automatically deleted once a month. So we built the tmp directory under the / data/hadoop directory:
2.1 looking at the / opt/software/hadoop/sbin/hadoop-daemon.sh file, it is found that the hadoop lookup pid is obtained according to the HADOOP_PID_DIR environment variable.
[hadoop@hadoop002 tmp] $cat / opt/software/hadoop/sbin/hadoop-daemon.sh | grep pid
# HADOOP_PID_DIR The pid files are stored. / tmp by default.
Pid=$HADOOP_PID_DIR/hadoop-$HADOOP_IDENT_STRING-$command.pid
If [- f $pid]; then
If kill-0 `cat $pid` > / dev/null 2 > & 1; then
Echo $command running as process `cat $pid`. Stop it first.
Echo $! > $pid
If [- f $pid]; then
TARGET_PID= `cat $pid`
Rm-f $pid
[hadoop@hadoop002 tmp] $
2.2 create the / data/hadoop/tem directory with root
[hadoop@hadoop002 hadoop] $exit # exit hadoop
Logout
[root@hadoop002 software] # cd /
[root@hadoop002 /] #
[root@hadoop002 /] # mkdir data
[root@hadoop002 /] # cd data/
[root@hadoop002 data] # mkdir hadoop
[root@hadoop002 data] # cd hadoop/
[root@hadoop002 hadoop] # mkdir tmp
[root@hadoop002 hadoop] # ll
Total 4
Drwxr-xr-x. 2 root root 4096 May 23 14:11 tmp
2.3 / data/hadoop/tem Directory Authorization
[root@hadoop002 hadoop] # chmod 777 tmp
[root@hadoop002 hadoop] # ll
Total 4
Drwxrwxrwx. 2 root root 4096 May 23 14:11 tmp
2.4 modify the environment variable of HADOOP_PID_DIR in the / opt/software/hadoop/etc/hadoop/hadoop-env.sh file
[hadoop@hadoop002 hadoop] $pwd
/ opt/software/hadoop/etc/hadoop
[hadoop@hadoop002 hadoop] $vi hadoop-env.sh
# export HADOOP_PID_DIR=$ {HADOOP_PID_DIR} # comment this line
Export HADOOP_PID_DIR=/data/hadoop/tmp # add a new path
After editing, save and exit.
2.5 restart sbin/start-dfs.sh
# stop the hadoop service first
[hadoop@hadoop002 sbin] $sh stop-dfs.sh
Stopping namenodes on [hadoop002]
Hadoop002: no namenode to stop
Hadoop002: no datanode to stop
Stopping secondary namenodes [hadoop002]
Hadoop002: no secondarynamenode to stop
# start the hadoop service again
[hadoop@hadoop002 sbin] $sh start-dfs.sh
Starting namenodes on [hadoop002]
Hadoop002: starting namenode, logging to / opt/software/hadoop-2.8.1/logs/hadoop-hadoop-namenode-hadoop002.out
Hadoop002: starting datanode, logging to / opt/software/hadoop-2.8.1/logs/hadoop-hadoop-datanode-hadoop002.out
Starting secondary namenodes [hadoop002]
Hadoop002: starting secondarynamenode, logging to / opt/software/hadoop-2.8.1/logs/hadoop-hadoop- secondarynamenode-hadoop002.out
[hadoop@hadoop002 sbin] $
# there are no files in the tmp directory before reboot
[root@hadoop002 ~] # cd / data/hadoop/tmp/
[root@hadoop002 tmp] # ll
Total 0
# after restart, the pid file is generated in the tmp directory
[root@hadoop002 tmp] # ll
Total 12
-rw-rw-r--. 1 hadoop hadoop 5 May 23 14:17 hadoop-hadoop-datanode.pid
-rw-rw-r--. 1 hadoop hadoop 5 May 23 14:17 hadoop-hadoop-namenode.pid
-rw-rw-r--. 1 hadoop hadoop 5 May 23 14:17 hadoop-hadoop-secondarynamenode.pid
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