Linux command notes - lyonwang/TechNotes GitHub Wiki

How Do I Find Out My Linux Distribution name and version

[lyonwang@UAT-Graylog ~]$ cat /etc/*-release
CentOS Linux release 7.2.1511 (Core)
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

CentOS Linux release 7.2.1511 (Core)
CentOS Linux release 7.2.1511 (Core)

How Do I Find Out My Kernel Version?

[lyonwang@UAT-Graylog ~]$ uname -a
Linux UAT-Graylog 3.10.0-327.el7.x86_64 #1 SMP Thu Nov 19 22:10:57 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

How Do I Find Out My Linux Kernel version and GCC version used to build?

[lyonwang@UAT-Graylog ~] cat /proc/version
Linux version 3.10.0-327.el7.x86_64 ([email protected]) (gcc version 4.8.3 20140911 (Red Hat 4.8.3-9) (GCC) ) #1 SMP Thu Nov 19 22:10:57 UTC 2015

How Do I Install Package for CentOS?

yum install perf

How CentOS 7 add user with sudo permission?

sudo adduser mynewuser
sudo passwd mynewuser
sudo visudo
mynewuser ALL=(ALL) ALL

How to increase centos 7 system/process(service) open file limit?

System

• check

sudo ulimit -a

• modify no persistent

sudo ulimit -HSn 102400

• modify with persistent (/etc/security/limits.conf add the following lines)

soft nofile 102400
hard nofile 102400

Increase open file limits in linux

Process or service

• check

sudo cat /proc/[process id]/limits
or
ls -l /proc/[process id]/fd | wc -l

• modify process get process id

sudo ps -ef | grep [process name]

modify by gdb (sudo gdb -p [process id])

(gdb) set $rlim = &{0ll, 0ll}
# the number 7 here is important. (the 7th item in check step)
(gdb) print getrlimit(7, $rlim)
(gdb) print *$rlim
# update the value retrieved above with getrlimit
(gdb) set *$rlim[0] = 40960
(gdb) print *$rlim
(gdb) print setrlimit(7, $rlim)

modify service add LimitNOFILE (sudo vim /usr/lib/systemd/system/[service name].service) and retart service

[Unit]
Description=...
After=network.target

[Service]
Restart=always
ExecStart=...
LimitNOFILE=40960

[Install]
WantedBy=multi-user.target