env

enter a sh session which has customer's environment

env - `cat ~/customer` /bin/sh

Date

date +%Y%m%d

20170831

date --date="1 day ago" +%F

2017-08-30

Mount

list device mount status

mount -l

mount all according to /etc/fstab

mount -a

umount

mount ${mount_point}

mount windows share folder with specific user by /etc/fstab

//${win_ip}/${share_name} /${local_mnt_point} cifs username=${share_user},password=${share password},uid=${local_user_id},gid=${local_group_id} 0 0

e.g.

//192.168.0.83/sync /mnae/m11_sync cifs username=mount_user,password=1234,uid=501,gid=501 0 0

Ulimit - Increase The Maximum Number Of Open Files / File Descriptors (FD)

User Level FD Limits

  • reboot required.

    # /etc/security/limits.conf
elk     soft    nofile          65536
elk     hard    nofile          65536

    # Ubuntu /etc/pam.d/common-session
session required pam_limits.so

  • check setting

    ulimit -Hn
ulimit -Sn

Awk

insert an new column before the 1st field

awk -F'\t' '{$1="NewField" FS $1;}1' OFS='\t' ol.tsv

where,

  • FS - Input field separator
  • OFS - output field separator
  • $1 - 1st field

chkconfig

  • To list the auditd service.

    chkconfig --list google-fluentd

  • To turn auditd off in runlevels 3, 4, and 5.

    chkconfig --level 2345 google-fluentd off

ssh-copy-id

copy public key into a remote machine's authorized_keys

ssh-copy-id -i ~/.ssh/id_rsa.pub $user@$domain

iconv

file character encoding converter.

convert a text file from big5 character encoding to utf8

iconv -f BIG5 -t UTF-8 big5.txt -o utf8.txt

iptables

redirect port 80 traffic to port 8080

iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080

persistent iptables setting

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