docker start起不來的解決辦法：1、檢查運(yùn)行狀態(tài)，然后通過“echo 3 > /proc/sys/vm/drop_caches”命令釋放被占用的內(nèi)存；2、通過“$netstat -nltp|grep ...”命令檢查端口是否已經(jīng)被占用，如果上線后發(fā)現(xiàn)占有，則改為可用端口再重啟即可。

本教程操作環(huán)境：linux7.3系統(tǒng)、docker19.03版、Dell G3電腦。

docker start起不來怎么辦？

Docker無法正常啟動的原因及解決辦法

概述

Docker啟動異常表現(xiàn)

狀態(tài)反復(fù)restaring，用命令查看

$docker ps -a
CONTAINER ID    IMAGE  COMMAND       CREATED      STATUS       PORTS    NAMES
21c09be88c11     docker.xxxx.cn:5000/xxx-tes/xxx_tes:1.0.6   "/usr/local/tomcat..."   9 days ago          Restarting (1) Less than a second ago                      xxx10

Docker日志有明顯問題：

$docker logs [容器名/容器ID]
比如：
docker logs openresty

Docker啟動異常的可能原因

內(nèi)存不夠

Docker 啟動至少需要2G內(nèi)存，首先執(zhí)行free -mh命令查看剩余內(nèi)存是否足夠

直接查看內(nèi)存

$free -mh
            total        used        free      shared  buff/cache   available
Mem:         15G         14G          627M        195M        636M     726M
Swap:         0B          0B          0B

分析日志

有時(shí)候一瞬間內(nèi)存過載溢出，導(dǎo)致部分進(jìn)程被殺死，看起來內(nèi)存也是夠用的，事實(shí)上docker還是會反復(fù)重啟，就需要通過docker日志和系統(tǒng)日志信的息來進(jìn)一步分析：

分析docker日志

查看docker日志看到內(nèi)存溢出的信息，要仔細(xì)翻閱才能找到信息，并不是在最下面

$docker logs [容器名/容器ID]|less 
Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x0000000769990000, 1449590784, 0) failed; error='Cannot allocate memory' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# An error report file with more information is saved as:
# //hs_err_pid1.log
Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x0000000769990000, 1449590784, 0) failed; error='Cannot allocate memory' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# An error report file with more information is saved as:
# /tmp/hs_err_pid1.log
Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x0000000769990000, 1449590784, 0) failed; error='Cannot allocate memory' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# Can not save log file, dump to screen..
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 1449590784 bytes for committing reserved memory.
# Possible reasons:
#   The system is out of physical RAM or swap space
#   In 32 bit mode, the process size limit was hit
# Possible solutions:
#   Reduce memory load on the system
#   Increase physical memory or swap space
#   Check if swap backing store is full
#   Use 64 bit Java on a 64 bit OS
#   Decrease Java heap size (-Xmx/-Xms)
#   Decrease number of Java threads
#   Decrease Java thread stack sizes (-Xss)
#   Set larger code cache with -XX:ReservedCodeCacheSize=
# This output file may be truncated or incomplete.
#
#  Out of Memory Error (os_linux.cpp:2756), pid=1, tid=140325689620224
#
# JRE version:  (7.0_79-b15) (build )
# Java VM: Java HotSpot(TM) 64-Bit Server VM (24.79-b02 mixed mode linux-amd64 compressed oops)
# Core dump written. Default location: //core or core.1
#

分析系統(tǒng)日志

查看系統(tǒng)日志，發(fā)現(xiàn)有大量由于內(nèi)存溢出，進(jìn)程被殺死的記錄

$grep -i 'Out of Memory' /var/log/messages
Apr  7 10:04:02 centos106 kernel: Out of memory: Kill process 1192 (java) score 54 or sacrifice child
Apr  7 10:08:00 centos106 kernel: Out of memory: Kill process 2301 (java) score 54 or sacrifice child
Apr  7 10:09:59 centos106 kernel: Out of memory: Kill process 28145 (java) score 52 or sacrifice child
Apr  7 10:20:40 centos106 kernel: Out of memory: Kill process 2976 (java) score 54 or sacrifice child
Apr  7 10:21:08 centos106 kernel: Out of memory: Kill process 3577 (java) score 47 or sacrifice child
Apr  7 10:21:08 centos106 kernel: Out of memory: Kill process 3631 (java) score 47 or sacrifice child
Apr  7 10:21:08 centos106 kernel: Out of memory: Kill process 3634 (java) score 47 or sacrifice child
Apr  7 10:21:08 centos106 kernel: Out of memory: Kill process 3640 (java) score 47 or sacrifice child
Apr  7 10:21:08 centos106 kernel: Out of memory: Kill process 3654 (java) score 47 or sacrifice child
Apr  7 10:27:27 centos106 kernel: Out of memory: Kill process 6998 (java) score 51 or sacrifice child
Apr  7 10:27:28 centos106 kernel: Out of memory: Kill process 7027 (java) score 52 or sacrifice child
Apr  7 10:28:10 centos106 kernel: Out of memory: Kill process 7571 (java) score 42 or sacrifice child
Apr  7 10:28:10 centos106 kernel: Out of memory: Kill process 7586 (java) score 42 or sacrifice child

端口沖突

該docker監(jiān)聽端口已經(jīng)被其他進(jìn)程占用，一般此種問題容易出現(xiàn)在新部署的服務(wù)，或在原有機(jī)器上部署新的后臺服務(wù)，所以在部署之前應(yīng)該執(zhí)行命令檢查端口是否已經(jīng)被占用，如果上線后發(fā)現(xiàn)占有則應(yīng)改為可用端口再重啟之。

檢查命令：    netstat -nltp|grep [規(guī)劃的端口號]

解決方案

內(nèi)存不夠的方案

進(jìn)程在運(yùn)行一段時(shí)間后占用大量內(nèi)存，需要將其重啟。重啟命令可能有時(shí)并不起作用。主要檢查運(yùn)行狀態(tài)，如果未成功停止，則重新重啟；

ELK日志收集程序或者其他java進(jìn)程占用過高，用top和ps命令排查，謹(jǐn)慎確定進(jìn)程的作用，在確保不影響業(yè)務(wù)的情況下，停止相關(guān)進(jìn)程；

釋放被占用的內(nèi)存（buff/cache）

 [root]# sync  #將內(nèi)存數(shù)據(jù)寫入磁盤
 [root]# echo 3 > /proc/sys/vm/drop_caches  #釋放被占用的內(nèi)存

有時(shí)候并不是buff/cache過高導(dǎo)致內(nèi)存不夠用，確實(shí)是被很多必要的進(jìn)程消耗掉了內(nèi)存，那就需要從機(jī)器資源分配使用的層面去考慮和解決了。

端口沖突的對策

一般此種問題容易出現(xiàn)在新部署的服務(wù)，或在原有機(jī)器上部署新的后臺服務(wù)，所以在部署之前應(yīng)該執(zhí)行命令檢查端口是否已經(jīng)被占用，如果上線后發(fā)現(xiàn)占有則應(yīng)改為可用端口再重啟之。

檢查命令：    $netstat -nltp|grep [規(guī)劃的端口號]

推薦學(xué)習(xí)：《docker視頻教程》

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