Linux 系統管理與安全：基本 Linux 系統知識

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$ man [section] <program>
LS(1) User Commands LS(1)
NAME
ls -‐ list directory contents
SYNOPSIS
ls [OPTION]... [FILE]...
DESCRIPTION
List information about the FILEs (the current directory by default). Sort entries alphabeti-‐
cally if none of -‐cftuvSUX nor -‐-‐sort is specified.
Mandatory arguments to long options are mandatory for short options too.
-‐a, -‐-‐all
do not ignore entries starting with .

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• $ echo -‐e "abcna"
abc
a

• STDIN (0)
• STDOUT (1)
• STDERR (2)
• $ cat /etc/passwd > users.txt
(STDOUT)-‐
• $ cat /etc/passwd >> users.txt
(STDOUT)-‐
• $ mail -‐s "Test mail" < letter.txt
(STDIN)

• $ cat /etc/passwd 2> errors.txt
( STDERR)
• $ find /etc > /dev/null
( STDOUT)
• $ sh script.sh > /dev/null 2>&1
( )
• $ sh script.sh | tee -‐a log.txt | other_program
( log.txt other_program)
• $ sh script.sh | xargs other_program
( other_program )

• |
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• $ cat /etc/passwd | program

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• users.txt snowman
$ grep snowman users.txt
• txt snowman
$ grep snowman *.txt
• $ ifconfig | grep 'eth0' -‐-‐color=auto
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$ grep -‐r 'some_text' /etc/
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$ grep –e '^Snowman$' users.txt

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• $ find [ ] [ ]
• -‐name
• -‐perm
• -‐type
• -‐mtime
• $ find /etc -‐name passwd

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•
• $ sed [ ] < >
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•

•
• awk ' '
• awk '{ }' {}
• awk ' { }' {}
• sed awk

• tab
$ last -‐n 5 | awk '{print $1 "t" $3}'
• $ free -‐h
total used free shared buffers cached
Mem: 7.8G 7.6G 168M 18M 440M 3.0G
-‐/+ buffers/cache: 4.1G 3.6G
2.0G 232K 2.0G
• $ free -‐h | awk '/Mem/{print $3}'
7.6G

• STDIN
• /tmp core
$ find /tmp -‐name '*core*' -‐type f -‐print | xargs
/bin/rm -‐f
• /etc 664
$ find /etc -‐perm -‐664 | xargs ls –l

• cat
• head
• tail
• sort
• more/less
• nl
• cut
• uniq
• wc

• $ cat /proc/loadavg
0.48 0.47 0.55 2/347 9893
• $ cat /proc/loadavg | [...]
0.48
• $ cat /proc/meminfo
MemTotal: 8138396 kB
MemFree: 2895168 kB
Buffers: 599540 kB
...
• $ cat /proc/meminfo | [...]
2895168

1. $ cat /proc/loadavg | awk '{print $1}'
2. $ cat /proc/meminfo | grep MemFree | awk '{print $2}'

• ls
• cd <path>
• pwd
• file <file>
• mkdir <folder>
• rmdir <folder>
• touch <filename>
• ln <destination> <source>

$ ls -‐al
-‐rwxr-‐xr-‐-‐ 1 sntc06 sntc06 2.6K Oct 8 2012 action.php
-‐rwxr-‐xr-‐-‐
-‐: regular file
d: directory
l: symbolic link
c: character device
b: block device
s: socket
p: named pipe

$ ls -‐al
Owner permission
r: read
w: write
x: execute
Group:
r-‐x
Others:
r-‐-‐

$ ls -‐al
Owner permission
r: 100: 4
w: 010: 2
x: 001: 1
-‐> 754
Example:
$ chmod 644 action.php
$ chmod a+x action.php
$ chmod -‐w action.php

$ ls -‐al

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•
• # mount /dev/sdd1 /media/usb-‐drive
• # mount -‐o remount,ro -‐t ext4 /dev/sda1 /home
-‐o [ ] -‐t [ ]
•
# umount /media/usb-‐drive

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• init / systemd
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• process
$ ps -‐l
• process
# ps axu
• process tree
# ps axjf
1 2827 2827 2827 ? -‐1 Ss 1003 0:00 SCREEN
2827 2828 2828 2828 pts/4 2836 Ss 1003 0:00 _ /bin/zsh
2828 2836 2836 2828 pts/4 2836 S+ 1003 0:00 | _ /bin/bash ./start.sh
2836 2837 2836 2828 pts/4 2836 Sl+ 1003 207:14 | _ java -‐server …
2827 3025 3025 3025 pts/8 3025 Ss+ 1003 0:00 _ /bin/zsh
root 27850 0.0 0.0 113908 4332 ? Ss Apr01 0:00 sshd: sntc06 [priv]
sntc06 27976 0.0 0.0 114048 2080 ? S Apr01 0:00 sshd: sntc06@pts/6
sntc06 27977 0.0 0.0 52076 6388 pts/6 Ss+ Apr01 0:00 -‐zsh
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
0 S 1000 8755 8754 0 80 0 -‐ 12210 sigsus pts/11 00:00:00 zsh
0 R 1000 9082 8755 0 80 0 -‐ 3383 -‐ pts/11 00:00:00 ps

• Ctrl+Z
• fg
• bg
• jobs
• shell &
$ ping localhost &

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•
No.
1 SIGHUP log file
2 SIGINT Interrupt (Ctrl+C)
3 SIGQUIT
9 SIGKILL
15 SIGTERM
18 SIGCONT
19 SIGSTP (Ctrl+Z)
$ man 7 signal

• pid
• kill [-‐signal] <pid>
• PID 5566
# kill 5566
# kill -‐15 5566
• PID 5566
# kill -‐9 5566
• PGID 5566
# kill -‐1 -‐5566
( )

• PID
• root PID
$ pgrep -‐u root -‐l
• httpd
$ pgrep httpd -‐l

•
• pkill [-‐signal] < >
• httpd
# pkill httpd
• httpd
# pkill -‐9 httpd

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• /etc/rcX.d/
• /etc/init.d/

• sysvinit upstart
init
•
$ systemctl
• / /
# systemctl start/stop/restart <service>
• /
# systemctl status/is-‐enabled <service>
• /
# systemctl enable/disable <service>

root:~/ # systemctl status httpd
httpd.service -‐ The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
Active: active (running) since 2015-‐04-‐01 16:10:40 CST; 10min ago
Main PID: 1221 (httpd)
Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
CGroup: /system.slice/httpd.service
├─1221 /usr/sbin/httpd -‐DFOREGROUND
└─2479 /usr/sbin/httpd -‐DFOREGROUND
4 01 16:10:37 localhost.localdomain httpd[1221]: AH00558: httpd: ...
4 01 16:10:40 localhost.localdomain systemd[1]: Started The Apache HTTP Server.
Hint: Some lines were ellipsized, use -‐l to show in full.

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[Unit]
Description=The Apache HTTP Server
After=network.target remote-‐fs.target nss-‐lookup.target
[Service]
Type=notify
EnvironmentFile=/etc/sysconfig/httpd
ExecStart=/usr/sbin/httpd $OPTIONS -‐DFOREGROUND
ExecReload=/usr/sbin/httpd $OPTIONS -‐k graceful
ExecStop=/bin/kill -‐WINCH ${MAINPID}
# We want systemd to give httpd some time to finish gracefully, but still want
# it to kill httpd after TimeoutStopSec if something went wrong during the
# graceful stop. Normally, Systemd sends SIGTERM signal right after the
# ExecStop, which would kill httpd. We are sending useless SIGCONT here to give
# httpd time to finish.
KillSignal=SIGCONT
PrivateTmp=true
[Install]
WantedBy=multi-‐user.target

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• at
• crontab
•
$ crontab -‐l
•
$ crontab -‐e
• root
# crontab -‐u root
root:/dev/ # at 18:30 2015-‐04-‐01
at> echo "Happy April Fools!" > /dev/pts/0
at> <EOT>
job 2 at Wed Apr 1 18:20:00 2015

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• /etc/crontab, /etc/cron.d/
SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
#m h dom mon dow user command
0 0 * * 1 root /bukkit_backup/backup.sh >> /dev/null 2>&1
*/30 8-‐17 * * 1-‐5 root /root/check_website.sh

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• /etc/cron.daily/
• /etc/cron.weekly/
• /etc/cron.monthly/
#period in days delay in minutes job-‐identifier command
1 5 cron.daily nice run-‐parts /etc/cron.daily
7 25 cron.weekly nice run-‐parts /etc/cron.weekly
@monthly 45 cron.monthly nice run-‐parts /etc/cron.monthly

• *.rpm
•
# rpm -‐i package.rpm
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# rpm -‐U package.rpm
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# rpm -‐i package.rpm -‐-‐test -‐v
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# rpm -‐e package
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# rpm -‐q -‐a

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# yum check-‐update
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# yum update mosh
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# yum install mosh
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# yum remove mosh

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# yum list installed
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# yum search mosh
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# yum info mosh

• /etc/passwd
•
• /etc/group
•
root:x:0:0:root:/root:/bin/zsh
root:x:0:user1,user2

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$ passwd
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# passwd sntc06

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# useradd [ ] < >
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• -‐m
• -‐c
• -‐u UID
• -‐g GID
• -‐G
• -‐s login shell

• admin
# groupadd admin
• test
# groupdel test
• snowman admin
# usermod -‐a -‐G admin snowman

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$ su -‐ root ( login shell)
$ su ( shell)
• snowman
$ su snowman

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• snowman
$ sudo -‐u snowman vim test.txt
• root
$ sudo reboot
• root shell
$ sudo su -‐

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## Allow root to run any commands anywhere
root ALL=(ALL) ALL
## Allows people in group wheel to run all commands
%wheel ALL=(ALL) ALL

1.
2. sudo
3. su
4. sudo mariadb

Linux 系統管理與安全：基本 Linux 系統知識

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