2.1/2.2 系统目录结构

ls命令可以列写目录，可以看一下根目录下的内容。

1[root@lhy ~]# ls /
2bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

root用户的家目录就在/root/

1[root@lhy ~]# ls /root
2anaconda-ks.cfg  openscap_data

家目录用于存储用户的配置文件和普通文件，比如

1[root@lhy ~]# ls /root/.ssh/authorized_keys 
2/root/.ssh/authorized_keys

如果我希望通过ssh连接一个普通的非root用户，那么就需要把这个配置文件（公钥）放置在对应用户的家目录里（/etc/ssh/sshd_config文件规定的）。比如，新建一个用户lhy01，这个配置文件就需要放置在/home/lhy01/下，这个目录在创建用户时候会自动创建。

1[root@lhy ~]# useradd lhy01
2[root@lhy ~]# ls /home/
3lhy01
4[root@lhy ~]# ls /home/lhy01/ -a
5.  ..  .bash_logout  .bash_profile  .bashrc

想查看一个目录有什么子目录，可以用tree命令。如果没有安装可以用yum安装。

1[root@lhy ~]# yum install tree -y
2Loaded plugins: fastestmirror
3base                                                                                                | 3.6 kB  00:00:00     
4extras                                                                                              | 3.4 kB  00:00:00     
5updates                                                                                             | 3.4 kB  00:00:00     
6(1/2): extras/7/x86_64/primary_db                                                                   | 147 kB  00:00:00     
7(2/2): updates/7/x86_64/primary_db                                                                  | 2.0 MB  00:00:00     
8Loading mirror speeds from cached hostfile
9 * base: mirrors.huaweicloud.com
10 * extras: mirrors.163.com
11 * updates: mirrors.huaweicloud.com
12Resolving Dependencies
13--> Running transaction check
14---> Package tree.x86_64 0:1.6.0-10.el7 will be installed
15--> Finished Dependency Resolution
16
17Dependencies Resolved
18
19===========================================================================================================================
20 Package                   Arch                        Version                             Repository                 Size
21===========================================================================================================================
22Installing:
23 tree                      x86_64                      1.6.0-10.el7                        base                       46 k
24
25Transaction Summary
26===========================================================================================================================
27Install  1 Package
28
29Total download size: 46 k
30Installed size: 87 k
31Downloading packages:
32tree-1.6.0-10.el7.x86_64.rpm                                                                        |  46 kB  00:00:00     
33Running transaction check
34Running transaction test
35Transaction test succeeded
36Running transaction
37  Installing : tree-1.6.0-10.el7.x86_64                                                                                1/1 
38  Verifying  : tree-1.6.0-10.el7.x86_64                                                                                1/1 
39
40Installed:
41  tree.x86_64 0:1.6.0-10.el7                                                                                               
42
43Complete!

tree可以简单的可以显示一个文档

tree /

但是由于文件过于多，可能突破Xshell的ScrollBack上限。我们用参数来显示两层目录。查看tree的用法有两种，一种是用tree本身来看，另一种是用Manual Page命令。

1[root@lhy ~]# tree --help
2usage: tree [-acdfghilnpqrstuvxACDFQNSUX] [-H baseHREF] [-T title ] [-L level [-R]]
3	[-P pattern] [-I pattern] [-o filename] [--version] [--help] [--inodes]
4	[--device] [--noreport] [--nolinks] [--dirsfirst] [--charset charset]
5	[--filelimit[=]#] [--si] [--timefmt[=]<f>] [<directory list>]
6  ------- Listing options -------
7  -a            All files are listed.
8  -d            List directories only.
9  -l            Follow symbolic links like directories.
10  -f            Print the full path prefix for each file.
11  -x            Stay on current filesystem only.
12  -L level      Descend only level directories deep.
13  -R            Rerun tree when max dir level reached.
14  -P pattern    List only those files that match the pattern given.
15  -I pattern    Do not list files that match the given pattern.
16  --noreport    Turn off file/directory count at end of tree listing.
17  --charset X   Use charset X for terminal/HTML and indentation line output.
18  --filelimit # Do not descend dirs with more than # files in them.
19  --timefmt <f> Print and format time according to the format <f>.
20  -o filename   Output to file instead of stdout.
21  --du          Print directory sizes.
22  --prune       Prune empty directories from the output.
23  -------- File options ---------
24  -q            Print non-printable characters as '?'.
25  -N            Print non-printable characters as is.
26  -Q            Quote filenames with double quotes.
27  -p            Print the protections for each file.
28  -u            Displays file owner or UID number.
29  -g            Displays file group owner or GID number.
30  -s            Print the size in bytes of each file.
31  -h            Print the size in a more human readable way.
32  --si          Like -h, but use in SI units (powers of 1000).
33  -D            Print the date of last modification or (-c) status change.
34  -F            Appends '/', '=', '*', '@', '|' or '>' as per ls -F.
35  --inodes      Print inode number of each file.
36  --device      Print device ID number to which each file belongs.
37  ------- Sorting options -------
38  -v            Sort files alphanumerically by version.
39  -r            Sort files in reverse alphanumeric order.
40  -t            Sort files by last modification time.
41  -c            Sort files by last status change time.
42  -U            Leave files unsorted.
43  --dirsfirst   List directories before files (-U disables).
44  ------- Graphics options ------
45  -i            Don't print indentation lines.
46  -A            Print ANSI lines graphic indentation lines.
47  -S            Print with ASCII graphics indentation lines.
48  -n            Turn colorization off always (-C overrides).
49  -C            Turn colorization on always.
50  ------- XML/HTML options -------
51  -X            Prints out an XML representation of the tree.
52  -H baseHREF   Prints out HTML format with baseHREF as top directory.
53  -T string     Replace the default HTML title and H1 header with string.
54  --nolinks     Turn off hyperlinks in HTML output.
55  ---- Miscellaneous options ----
56  --version     Print version and exit.
57  --help        Print usage and this help message and exit.
58
59
60[root@lhy ~]# man tree
61
62TREE(1)                                         General Commands Manual                                         TREE(1)
63
64NAME
65       tree - list contents of directories in a tree-like format.
66
67SYNOPSIS
68       tree  [-acdfghilnpqrstuvxACDFQNSUX]  [-L level [-R]] [-H baseHREF] [-T title] [-o filename] [--nolinks] [-P pat‐
69       tern] [-I pattern] [--inodes] [--device] [--noreport] [--dirsfirst] [--version] [--help] [--filelimit #]  [--si]
70       [--prune] [--du] [--timefmt format] [directory ...]
71
72DESCRIPTION
73       Tree  is  a  recursive  directory listing program that produces a depth indented listing of files, which is col‐
74       orized ala dircolors if the LS_COLORS environment variable is set and output is to tty.  With no arguments, tree
75       lists  the  files in the current directory.  When directory arguments are given, tree lists all the files and/or
76       directories found in the given directories each in turn.   Upon  completion  of  listing  all  files/directories
77       found, tree returns the total number of files and/or directories listed.
78
79       By  default, when a symbolic link is encountered, the path that the symbolic link refers to is printed after the
80       name of the link in the format:
81
82           name -> real-path
83
84       If the `-l' option is given and the symbolic link refers to an actual directory, then tree will follow the  path
85       of the symbolic link as if it were a real directory.
86
87OPTIONS
88       Tree understands the following command line switches:
89
90LISTING OPTIONS
91       -a     All files are printed.  By default tree does not print hidden files (those beginning with a dot `.').  In
92              no event does tree print the file system constructs `.' (current directory)  and  `..'  (previous  direc‐
93              tory).
94
95       -d     List directories only.
96
97       -l     Follows  symbolic  links  if  they point to directories, as if they were directories. Symbolic links that
98              will result in recursion are avoided when detected.
99
100       -f     Prints the full path prefix for each file.
101
102       -x     Stay on the current file-system only.  Ala find -xdev.
103
104       -L level
105              Max display depth of the directory tree.
106
107       -R     Recursively cross down the tree each level directories (see -L option), and at each of them execute  tree
108              again adding `-o 00Tree.html' as a new option.
109
110       -P pattern
111              List  only  those  files that match the wild-card pattern.  Note: you must use the -a option to also con‐
112              sider those files beginning with a dot `.'  for matching.  Valid wildcard operators are `*' (any zero  or
113              more  characters),  `?'  (any  single  character),  `[...]' (any single character listed between brackets
114              (optional - (dash) for character range may be used: ex: [A-Z]), and `[^...]' (any  single  character  not
115              listed in brackets) and `|' separates alternate patterns.
116
117       -I pattern
118              Do not list those files that match the wild-card pattern.
119
120       --prune
121              Makes  tree  prune empty directories from the output, useful when used in conjunction with -P or -I.  See
122              BUGS AND NOTES below for more information on this option.
123
124       --noreport
125              Omits printing of the file and directory report at the end of the tree listing.
126
127       --charset charset
128              Set the character set to use when outputting HTML and for line drawing.
129
130       --filelimit #
131              Do not descend directories that contain more than # entries.
132
133
134       --timefmt format
135              Prints (implies -D) and formats the date according to the format string which uses the  strftime(3)  syn‐
136              tax.
137
138       -o filename
139              Send output to filename.
140
141FILE OPTIONS
142       -q     Print non-printable characters in filenames as question marks instead of the default.
143
144       -N     Print non-printable characters as is instead of as escaped octal numbers.
145
146       -Q     Quote the names of files in double quotes.
147
148       -p     Print the file type and permissions for each file (as per ls -l).
149
150       -u     Print the username, or UID # if no username is available, of the file.
151
152       -g     Print the group name, or GID # if no group name is available, of the file.
153
154       -s     Print the size of each file in bytes along with the name.
155
156       -h     Print  the size of each file but in a more human readable way, e.g. appending a size letter for kilobytes
157              (K), megabytes (M), gigabytes (G), terabytes (T), petabytes (P) and exabytes (E).
158
159       --si   Like -h but use SI units (powers of 1000) instead.
160
161       --du   For each directory report its size as the accumulation of sizes of all its files and sub-directories (and
162              their  files, and so on).  The total amount of used space is also given in the final report (like the 'du
163              -c' command.) This option requires tree to read the entire directory tree before emitting  it,  see  BUGS
164              AND NOTES below.  Implies -s.
165
166       -D     Print  the  date of the last modification time or if -c is used, the last status change time for the file
167              listed.
168
169       -F     Append a `/' for directories, a `=' for socket files, a  `*'  for  executable  files,  a  `>'  for  doors
170              (Solaris) and a `|' for FIFO's, as per ls -F
171
172       -F     Append a `/' for directories, a `=' for socket files, a  `*'  for  executable  files,  a  `>'  for  doors
173              (Solaris) and a `|' for FIFO's, as per ls -F
174
175       --inodes
176              Prints the inode number of the file or directory
177
178       --device
179              Prints the device number to which the file or directory belongs
180
181SORTING OPTIONS
182       -v     Sort the output by version.
183
184       -r     Sort the output in reverse alphabetic order.
185
186       -t     Sort the output by last modification time instead of alphabetically.
187
188       -c     Sort  the  output  by  last status change instead of alphabetically.  Modifies the -D option (if used) to
189              print the last status change instead of modification time.
190
191       -U     Do not sort.  Lists files in directory order. Disables --dirsfirst.
192
193       --dirsfirst
194              List directories before files. This is a meta-sort that alters the above sorts.  This option is  disabled
195              when -U is used.
196
197GRAPHICS OPTIONS
198       -i     Makes tree not print the indentation lines, useful when used in conjunction with the -f option.
199
200       -A     Turn on ANSI line graphics hack when printing the indentation lines.
201
202       -S     Turn  on  ASCII line graphics (useful when using Linux console mode fonts). This option is now equivalent
203              to `--charset=IBM437' and may eventually be depreciated.
204
205       -n     Turn colorization off always, over-ridden by the -C option.
206
207       -C     Turn colorization on always, using built-in color defaults if the LS_COLORS environment variable  is  not
208              set.  Useful to colorize output to a pipe.
209
210XML/HTML OPTIONS
211       -X     Turn on XML output. Outputs the directory tree as an XML formatted file.
212
213       -H baseHREF
214              Turn  on HTML output, including HTTP references. Useful for ftp sites.  baseHREF gives the base ftp loca‐
215              tion when using HTML output. That is, the local directory may be `/local/ftp/pub', but it must be  refer‐
216              enced   as   `ftp://hostname.organization.domain/pub'   (baseHREF   should  be  `ftp://hostname.organiza‐
217              tion.domain'). Hint: don't use ANSI lines with this option, and don't give more than one directory in the
218              directory  list.  If  you  wish  to use colors via CCS style-sheet, use the -C option in addition to this
219              option to force color output.
220
221       -T title
222              Sets the title and H1 header string in HTML output mode.
223
224       --nolinks
225              Turns off hyperlinks in HTML output.
226
227MISC OPTIONS
228       --help Outputs a verbose usage listing.
229
230       --version
231              Outputs the version of tree.
232
233FILES
234       /etc/DIR_COLORS          System color database.
235       ~/.dircolors        Users color database.
236
237
238ENVIRONMENT
239       LS_COLORS      Color information created by dircolors
240       TREE_COLORS    Uses this for color information over LS_COLORS if it is set.
241       TREE_CHARSET   Character set for tree to use in HTML mode.
242       LC_CTYPE       Locale for filename output.
243       LC_TIME        Locale for timefmt output, see strftime(3).
244       TZ             Timezone for timefmt output, see strftime(3).
245
246AUTHOR
247       Steve Baker (ice@mama.indstate.edu)
248       HTML output hacked by Francesc Rocher (rocher@econ.udg.es)
249       Charsets and OS/2 support by Kyosuke Tokoro (NBG01720@nifty.ne.jp)
250
251BUGS AND NOTES
252       Tree does not prune "empty" directories when the -P and -I options are used by default. Use the --prune option.
253
254       The -h and --si options round to the nearest whole number unlike the ls implementations which rounds up always.
255
256       Pruning files and directories with the -I, -P and --filelimit options  will  lead  to  incorrect  file/directory
257       count reports.
258
259       The  --prune  and  --du options cause tree to accumulate the entire tree in memory before emitting it. For large
260       directory trees this can cause a significant delay in output and the use of large amounts of memory.
261
262       The timefmt expansion buffer is limited to a ridiculously large 255 characters.  Output of time  strings  longer
263       than this will be undefined, but are guaranteed to not exceed 255 characters.
264
265       XML trees are not colored, which is a bit of a shame.
266
267       Probably more.
268
269SEE ALSO
270       dircolors(1), ls(1), find(1), du(1), strftime(3)
271
272Tree 1.6.0     
273
274 Manual page tree(1) line 1 (press h for help or q to quit)

可以看到用-L参数可以设置最深搜索层数，-d只显示文件夹。

1[root@lhy ~]# tree / -L 2 -d
2/
3├── bin -> usr/bin
4├── boot
5│   ├── efi
6│   ├── grub
7│   └── grub2
8├── dev
9│   ├── block
10│   ├── bsg
11│   ├── bus
12│   ├── char
13│   ├── cpu
14│   ├── disk
15│   ├── dri
16│   ├── fd -> /proc/self/fd
17│   ├── hugepages
18│   ├── input
19│   ├── mapper
20│   ├── mqueue
21│   ├── net
22│   ├── pts
23│   ├── raw
24│   ├── shm
25│   ├── snd
26│   └── vfio
27├── etc
28│   ├── alternatives
29│   ├── audisp
30│   ├── audit
31│   ├── bash_completion.d
32│   ├── binfmt.d
33│   ├── chkconfig.d
34│   ├── cron.d
35│   ├── cron.daily
36│   ├── cron.hourly
37│   ├── cron.monthly
38│   ├── cron.weekly
39│   ├── dbus-1
40│   ├── default
41│   ├── depmod.d
42│   ├── dhcp
43│   ├── dracut.conf.d
44│   ├── firewalld
45│   ├── gcrypt
46│   ├── gnupg
47│   ├── groff
48│   ├── grub.d
49│   ├── gss
50│   ├── init.d -> rc.d/init.d
51│   ├── iproute2
52│   ├── kernel
53│   ├── krb5.conf.d
54│   ├── ld.so.conf.d
55│   ├── libnl
56│   ├── logrotate.d
57│   ├── modprobe.d
58│   ├── modules-load.d
59│   ├── my.cnf.d
60│   ├── NetworkManager
61│   ├── openldap
62│   ├── opt
63│   ├── pam.d
64│   ├── pkcs11
65│   ├── pki
66│   ├── plymouth
67│   ├── pm
68│   ├── polkit-1
69│   ├── popt.d
70│   ├── postfix
71│   ├── ppp
72│   ├── prelink.conf.d
73│   ├── profile.d
74│   ├── python
75│   ├── rc0.d -> rc.d/rc0.d
76│   ├── rc1.d -> rc.d/rc1.d
77│   ├── rc2.d -> rc.d/rc2.d
78│   ├── rc3.d -> rc.d/rc3.d
79│   ├── rc4.d -> rc.d/rc4.d
80│   ├── rc5.d -> rc.d/rc5.d
81│   ├── rc6.d -> rc.d/rc6.d
82│   ├── rc.d
83│   ├── rpm
84│   ├── rsyslog.d
85│   ├── rwtab.d
86│   ├── sasl2
87│   ├── security
88│   ├── selinux
89│   ├── sgml
90│   ├── skel
91│   ├── ssh
92│   ├── ssl
93│   ├── statetab.d
94│   ├── sudoers.d
95│   ├── sysconfig
96│   ├── sysctl.d
97│   ├── systemd
98│   ├── terminfo
99│   ├── tmpfiles.d
100│   ├── tuned
101│   ├── udev
102│   ├── vmware-tools
103│   ├── wpa_supplicant
104│   ├── X11
105│   ├── xdg
106│   ├── xinetd.d
107│   ├── xml
108│   ├── yum
109│   └── yum.repos.d
110├── home
111│   └── lhy01
112├── lib -> usr/lib
113├── lib64 -> usr/lib64
114├── media
115├── mnt
116├── opt
117├── proc
118│   ├── 1
119│   ├── 10
120│   ├── 11
121│   ├── acpi
122│   ├── asound
123│   ├── bus
124│   ├── driver
125│   ├── fs
126│   ├── irq
127│   ├── mpt
128│   ├── net -> self/net
129│   ├── scsi
130│   ├── self -> 1879
131│   ├── sys
132│   ├── sysvipc
133│   └── tty
134├── root
135│   └── openscap_data
136├── run
137│   ├── console
138│   ├── dbus
139│   ├── faillock
140│   ├── firewalld
141│   ├── initramfs
142│   ├── lock
143│   ├── log
144│   ├── mount
145│   ├── netreport
146│   ├── NetworkManager
147│   ├── plymouth
148│   ├── sepermit
149│   ├── setrans
150│   ├── sudo
151│   ├── systemd
152│   ├── tmpfiles.d
153│   ├── tuned
154│   ├── udev
155│   ├── user
156│   └── vmware
157├── sbin -> usr/sbin
158├── srv
159├── sys
160│   ├── block
161│   ├── bus
162│   ├── class
163│   ├── dev
164│   ├── devices
165│   ├── firmware
166│   ├── fs
167│   ├── hypervisor
168│   ├── kernel
169│   ├── module
170│   └── power
171├── tmp
172│   ├── systemd-private-72a51b409754493b803ada2e9f1e8ca6-vgauthd.service-SJRZXu
173│   ├── systemd-private-72a51b409754493b803ada2e9f1e8ca6-vmtoolsd.service-Ct0xiS
174│   ├── systemd-private-b5d827de47c64188ae996c7b05c8f1b2-vgauthd.service-SHMZTz
175│   └── systemd-private-b5d827de47c64188ae996c7b05c8f1b2-vmtoolsd.service-LXMW2A
176├── usr
177│   ├── bin
178│   ├── etc
179│   ├── games
180│   ├── include
181│   ├── lib
182│   ├── lib64
183│   ├── libexec
184│   ├── local
185│   ├── sbin
186│   ├── share
187│   ├── src
188│   └── tmp -> ../var/tmp
189└── var
190    ├── adm
191    ├── cache
192    ├── crash
193    ├── db
194    ├── empty
195    ├── games
196    ├── gopher
197    ├── kerberos
198    ├── lib
199    ├── local
200    ├── lock -> ../run/lock
201    ├── log
202    ├── mail -> spool/mail
203    ├── nis
204    ├── opt
205    ├── preserve
206    ├── run -> ../run
207    ├── spool
208    ├── tmp
209    └── yp
210
211370 directories

目录/usr/bin/  /usr/sbin/   /bin/  /sbin/ 这几个目录中保存的是一系列的命令。为什么直接敲命令而不需要执行具体目录下的文件，这是因为环境变量PATH的作用，这点之后再讲。

/sbin/下的命令一般是root用户的命令，普通用户下的命令一般是/bin/下的。

1[root@lhy ~]# ls /sbin/
2accessdb              e2fsck                     ip                 nl-link-list                sestatus
3addgnupghome          e2image                    ip6tables          nl-pktloc-lookup            setcap
4addpart               e2label                    ip6tables-restore  nl-qdisc-add                setenforce
5adduser               e2undo                     ip6tables-save     nl-qdisc-delete             setfiles
6agetty                e4defrag                   ipmaddr            nl-qdisc-list               setpci
7aide                  eapol_test                 iprconfig          nologin                     setsebool
8alternatives          ebtables                   iprdbg             nstat                       sfdisk
9anacron               ebtables-restore           iprdump            ownership                   shutdown
10applygnupgdefaults    ebtables-save              iprinit            packer                      slattach
11arp                   ether-wake                 iprsos             pam_console_apply           sln
12arpd                  ethtool                    iprupdate          pam_tally2                  smtp-sink
13arping                faillock                   ipset              pam_timestamp_check         smtp-source
14audispd               fdformat                   iptables           parted                      ss
15auditctl              fdisk                      iptables-restore   partprobe                   sshd
16auditd                filefrag                   iptables-save      partx                       sshd-keygen
17augenrules            findfs                     iptunnel           pidof                       sulogin
18aureport              firewalld                  irqbalance         ping6                       sushell
19ausearch              fixfiles                   kdump              pivot_root                  swaplabel
20authconfig            fsck                       kexec              plipconfig                  swapoff
21authconfig-tui        fsck.btrfs                 killall5           plymouthd                   swapon
22autrace               fsck.cramfs                kpartx             plymouth-set-default-theme  switch_root
23avcstat               fsck.ext2                  lchage             postalias                   sysctl
24badblocks             fsck.ext3                  ldattach           postcat                     sys-unconfig
25biosdecode            fsck.ext4                  ldconfig           postconf                    tc
26biosdevname           fsck.minix                 lgroupadd          postdrop                    telinit
27blkdeactivate         fsck.xfs                   lgroupdel          postfix                     tracepath
28blkdiscard            fsfreeze                   lgroupmod          postkick                    tracepath6
29blkid                 fstrim                     lid                postlock                    tune2fs
30blockdev              fxload                     lnewusers          postlog                     tuned
31bridge                genhomedircon              lnstat             postmap                     tuned-adm
32btrfs                 genhostid                  load_policy        postmulti                   udevadm
33btrfsck               genl                       logrotate          postqueue                   unix_chkpwd
34btrfs-convert         genl-ctrl-list             logsave            postsuper                   unix_update
35btrfs-debug-tree      getcap                     losetup            poweroff                    update-alternatives
36btrfs-find-root       getenforce                 lpasswd            ppp-watch                   update-pciids
37btrfs-image           getpcaps                   lsmod              pwck                        useradd
38btrfs-map-logical     getsebool                  lspci              pwconv                      userdel
39btrfs-select-super    glibc_post_upgrade.x86_64  luseradd           pwhistory_helper            usermod
40btrfstune             groupadd                   luserdel           pwunconv                    usernetctl
41btrfs-zero-log        groupdel                   lusermod           rdisc                       vigr
42build-locale-archive  groupmems                  makedumpfile       readprofile                 vipw
43cacertdir_rehash      groupmod                   matchpathcon       reboot                      virt-what
44capsh                 grpck                      mii-diag           resize2fs                   visudo
45cbq                   grpconv                    mii-tool           resizepart                  vmcore-dmesg
46cfdisk                grpunconv                  mkdict             restorecon                  vpddecode
47chcpu                 grub2-bios-setup           mkdumprd           rmmod                       weak-modules
48chkconfig             grub2-get-kernel-settings  mke2fs             route                       wipefs
49chpasswd              grub2-install              mkfs               routef                      wpa_cli
50chroot                grub2-mkconfig             mkfs.btrfs         routel                      wpa_passphrase
51clock                 grub2-ofpathname           mkfs.cramfs        rsyslogd                    wpa_supplicant
52clockdiff             grub2-probe                mkfs.ext2          rtacct                      xfs_admin
53consoletype           grub2-reboot               mkfs.ext3          rtcwake                     xfs_bmap
54cracklib-check        grub2-rpm-sort             mkfs.ext4          rtmon                       xfs_copy
55cracklib-format       grub2-set-default          mkfs.minix         rtpr                        xfs_db
56cracklib-packer       grub2-setpassword          mkfs.xfs           rtstat                      xfs_estimate
57cracklib-unpacker     grub2-sparc64-setup        mkhomedir_helper   runlevel                    xfs_freeze
58create-cracklib-dict  grubby                     mklost+found       runuser                     xfs_fsr
59crond                 halt                       mkswap             sasldblistusers2            xfs_growfs
60ctrlaltdel            hardlink                   modinfo            saslpasswd2                 xfs_info
61ctstat                hwclock                    modprobe           sefcontext_compile          xfs_io
62debugfs               iconvconfig                mount.fuse         selabel_digest              xfs_logprint
63delpart               iconvconfig.x86_64         nameif             selabel_lookup              xfs_mdrestore
64depmod                ifcfg                      netreport          selabel_lookup_best_match   xfs_metadump
65devlink               ifconfig                   NetworkManager     selabel_partial_match       xfs_mkfile
66dhclient              ifdown                     new-kernel-pkg     selinuxconlist              xfs_ncheck
67dhclient-script       ifenslave                  newusers           selinuxdefcon               xfs_quota
68dmfilemapd            ifstat                     nl-class-add       selinuxenabled              xfs_repair
69dmidecode             ifup                       nl-class-delete    selinuxexeccon              xfs_rtcp
70dmsetup               init                       nl-classid-lookup  selinux_restorecon          xtables-multi
71dmstats               insmod                     nl-class-list      semodule                    zdump
72dracut                install-info               nl-cls-add         sendmail                    zic
73dumpe2fs              installkernel              nl-cls-delete      sendmail.postfix            zramctl
74e2freefrag            intel-microcode2ucode      nl-cls-list        service
75[root@lhy ~]# ls /bin/
76[                     groups                 nl-link-set               sotruss
77a2p                   grub2-editenv          nl-link-stats             splain
78addr2line             grub2-file             nl-list-caches            split
79alias                 grub2-fstest           nl-list-sockets           sprof
80apropos               grub2-glue-efi         nl-monitor                sqlite3
81ar                    grub2-kbdcomp          nl-neigh-add              ssh
82arch                  grub2-menulst2cfg      nl-neigh-delete           ssh-add
83as                    grub2-mkfont           nl-neigh-list             ssh-agent
84aserver               grub2-mkimage          nl-neightbl-list          ssh-copy-id
85aulast                grub2-mklayout         nl-pktloc-lookup          ssh-keygen
86aulastlog             grub2-mknetdir         nl-qdisc-add              ssh-keyscan
87ausyscall             grub2-mkpasswd-pbkdf2  nl-qdisc-delete           ssltap
88auvirt                grub2-mkrelpath        nl-qdisc-list             stat
89awk                   grub2-mkrescue         nl-route-add              stdbuf
90base64                grub2-mkstandalone     nl-route-delete           strings
91basename              grub2-script-check     nl-route-get              strip
92bash                  grub2-syslinux2cfg     nl-route-list             stty
93bashbug               gsettings              nl-rule-list              su
94bashbug-64            gsoelim                nl-tctree-list            sudo
95bg                    gtar                   nl-util-addr              sudoedit
96bond2team             gtbl                   nm                        sudoreplay
97bootctl               gtroff                 nmcli                     sum
98busctl                gunzip                 nm-online                 sync
99c2ph                  gzexe                  nmtui                     systemctl
100cal                   gzip                   nmtui-connect             systemd-analyze
101ca-legacy             h2ph                   nmtui-edit                systemd-ask-password
102captoinfo             hdsploader             nmtui-hostname            systemd-cat
103cat                   head                   nohup                     systemd-cgls
104catchsegv             hexdump                nproc                     systemd-cgtop
105catman                hostid                 nroff                     systemd-coredumpctl
106cd                    hostname               nsenter                   systemd-delta
107centrino-decode       hostnamectl            numfmt                    systemd-detect-virt
108certutil              i386                   objcopy                   systemd-escape
109c++filt               iconv                  objdump                   systemd-firstboot
110chacl                 id                     od                        systemd-hwdb
111chage                 idiag-socket-details   oldfind                   systemd-inhibit
112chattr                idn                    open                      systemd-loginctl
113chcon                 igawk                  openssl                   systemd-machine-id-setup
114chfn                  info                   openvt                    systemd-notify
115chgrp                 infocmp                oscap                     systemd-nspawn
116chmod                 infokey                os-prober                 systemd-path
117chown                 infotocap              p11-kit                   systemd-run
118chrt                  install                passwd                    systemd-stdio-bridge
119chsh                  ionice                 paste                     systemd-sysv-convert
120chvt                  ipcalc                 pathchk                   systemd-tmpfiles
121cksum                 ipcmk                  pchrt                     systemd-tty-ask-password-agent
122clear                 ipcrm                  perl                      tabs
123cmp                   ipcs                   perl5.16.3                tac
124cmsutil               iptables-xml           perlbug                   tail
125col                   isosize                perldoc                   tailf
126colcrt                jobs                   perlthanks                tar
127colrm                 join                   pflags                    taskset
128column                journalctl             pgawk                     tbl
129comm                  kbdinfo                pgrep                     teamd
130command               kbd_mode               pic                       teamdctl
131coredumpctl           kbdrate                piconv                    teamnl
132cp                    kdumpctl               pinentry                  tee
133cpio                  kernel-install         pinentry-curses           test
134cpupower              kill                   ping                      testgdbm
135crlutil               kmod                   ping6                     tic
136crontab               last                   pinky                     timedatectl
137csplit                lastb                  pk12util                  timeout
138csslint-0.6           lastlog                pkaction                  tload
139curl                  lchfn                  pkcheck                   tmon
140cut                   lchsh                  pkexec                    toe
141date                  ld                     pkg-config                top
142db_archive            ld.bfd                 pkill                     touch
143db_checkpoint         ldd                    pkla-admin-identities     tput
144db_deadlock           ld.gold                pkla-check-authorization  tr
145db_dump               less                   pkttyagent                tracepath
146db_dump185            lessecho               pl2pm                     tracepath6
147db_hotbackup          lesskey                pldd                      tree
148db_load               lesspipe.sh            plymouth                  troff
149db_log_verify         lexgrog                pmap                      true
150db_printlog           link                   pod2html                  truncate
151db_recover            linux32                pod2man                   trust
152db_replicate          linux64                pod2text                  tset
153db_stat               linux-boot-prober      pod2usage                 tsort
154db_tuner              ln                     post-grohtml              tty
155db_upgrade            loadkeys               powernow-k8-decode        turbostat
156dbus-binding-tool     loadunimap             pr                        tzselect
157dbus-cleanup-sockets  locale                 preconv                   udevadm
158dbus-daemon           localectl              pre-grohtml               ul
159dbus-monitor          localedef              printenv                  ulockmgr_server
160dbus-send             logger                 printf                    umask
161dbus-uuidgen          login                  prlimit                   umount
162db_verify             loginctl               ps                        unalias
163dd                    logname                psed                      uname
164deallocvt             look                   psfaddtable               unexpand
165df                    ls                     psfgettable               unicode_start
166dgawk                 lsattr                 psfstriptable             unicode_stop
167diff                  lsblk                  psfxtable                 uniq
168diff3                 lscpu                  pstruct                   unlink
169dir                   lsinitrd               ptaskset                  unshare
170dircolors             lsipc                  ptx                       unxz
171dirname               lslocks                pwd                       update-ca-trust
172dmesg                 lslogins               pwdx                      update-mime-database
173dnsdomainname         lsns                   pwmake                    uptime
174domainname            lsscsi                 pwscore                   urlgrabber
175dracut                lua                    pydoc                     users
176du                    luac                   python                    usleep
177dumpkeys              machinectl             python2                   usx2yloader
178dwp                   mailq                  python2.7                 utmpdump
179echo                  mailq.postfix          ranlib                    uuidgen
180egrep                 make                   raw                       vdir
181eject                 makedb                 read                      VGAuthService
182elfedit               man                    readelf                   vi
183env                   mandb                  readlink                  view
184envsubst              manpath                realpath                  vim
185eqn                   mapscrn                recode-sr-latin           vimdiff
186ex                    mcookie                rename                    vimtutor
187expand                md5sum                 renice                    vlock
188expr                  mesg                   reset                     vmhgfs-fuse
189factor                mixartloader           resizecons                vmstat
190fallocate             mkdir                  rev                       vm-support
191false                 mkfifo                 rm                        vmtoolsd
192fc                    mkinitrd               rmail                     vmware-checkvm
193fg                    mknod                  rmail.postfix             vmware-guestproxycerttool
194fgconsole             mktemp                 rmdir                     vmware-hgfsclient
195fgrep                 modutil                rpcgen                    vmware-namespace-cmd
196file                  more                   rpm                       vmware-rpctool
197find                  mount                  rpm2cpio                  vmware-toolbox-cmd
198find2perl             mountpoint             rpmdb                     vmware-vgauth-cmd
199findmnt               msgattrib              rpmkeys                   vmware-xferlogs
200fipscheck             msgcat                 rpmquery                  vxloader
201fipshmac              msgcmp                 rpmverify                 w
202firewall-cmd          msgcomm                rsyslog-recover-qi.pl     wait
203firewall-offline-cmd  msgconv                runcon                    wall
204flock                 msgen                  run-parts                 watch
205fmt                   msgexec                rvi                       watchgnupg
206fold                  msgfilter              rview                     wc
207free                  msgfmt                 rvim                      wdctl
208fusermount            msggrep                s2p                       whatis
209gapplication          msghack                scp                       whereis
210gawk                  msginit                script                    which
211gdbus                 msgmerge               scriptreplay              whiptail
212gencat                msgunfmt               sdiff                     who
213genl-ctrl-list        msguniq                secon                     whoami
214geoiplookup           mv                     sed                       write
215geoiplookup6          namei                  seq                       x86_64
216geoipupdate           ndptool                setarch                   x86_energy_perf_policy
217geqn                  neqn                   setfacl                   xargs
218getconf               netstat                setfont                   xgettext
219getent                newaliases             setkeycodes               xmlcatalog
220getfacl               newaliases.postfix     setleds                   xmllint
221getkeycodes           newgrp                 setmetamode               xmlsec1
222getopt                nf-ct-add              setpriv                   xmlwf
223getopts               nf-ct-list             setsid                    xsltproc
224gettext               nf-exp-add             setterm                   xxd
225gettext.sh            nf-exp-delete          setup-nsssysinit          xz
226gio                   nf-exp-list            setup-nsssysinit.sh       xzcat
227gio-querymodules-64   nf-log                 setvtrgb                  xzcmp
228glib-compile-schemas  nf-monitor             sftp                      xzdec
229gmake                 nf-queue               sg                        xzdiff
230gneqn                 ngettext               sh                        xzegrep
231gnroff                nice                   sha1sum                   xzfgrep
232gpasswd               nisdomainname          sha224sum                 xzgrep
233gpg                   nl                     sha256sum                 xzless
234gpg2                  nl-addr-add            sha384sum                 xzmore
235gpg-agent             nl-addr-delete         sha512sum                 yes
236gpgconf               nl-addr-list           showconsolefont           ypdomainname
237gpg-connect-agent     nl-class-add           showkey                   yum
238gpg-error             nl-class-delete        shred                     zcat
239gpgparsemail          nl-classid-lookup      shuf                      zcmp
240gpgsplit              nl-class-list          signtool                  zdiff
241gpgv                  nl-cls-add             signver                   zegrep
242gpgv2                 nl-cls-delete          size                      zfgrep
243gpg-zip               nl-cls-list            skill                     zforce
244gpic                  nl-fib-lookup          slabtop                   zgrep
245gprof                 nl-link-enslave        sleep                     zless
246grep                  nl-link-ifindex2name   slogin                    zmore
247groff                 nl-link-list           snice                     znew
248grops                 nl-link-name2ifindex   soelim                    zsoelim
249grotty                nl-link-release        sort

/boot/下的文件是启动相关的文件，比如grub文件。比如删除了vmlinuz-3.10.0-693.el7.x86_64这些文件，你就不能正常启动这个系统了。

1[root@lhy ~]# ls /boot/
2config-3.10.0-693.el7.x86_64                             initramfs-3.10.0-693.el7.x86_64kdump.img
3efi                                                      initrd-plymouth.img
4grub                                                     symvers-3.10.0-693.el7.x86_64.gz
5grub2                                                    System.map-3.10.0-693.el7.x86_64
6initramfs-0-rescue-7b83625f83564e1691eca0a488be153c.img  vmlinuz-0-rescue-7b83625f83564e1691eca0a488be153c
7initramfs-3.10.0-693.el7.x86_64.img                      vmlinuz-3.10.0-693.el7.x86_64

/dev/文件是linux系统的特有的设备文件，鼠标、键盘、显示器等文件都保存在这里。

1[root@lhy ~]# ls /dev/
2agpgart          dmmidi     log                 port    shm       tty14  tty27  tty4   tty52  tty8     vcs    vfio
3autofs           dri        loop-control        ppp     snapshot  tty15  tty28  tty40  tty53  tty9     vcs1   vga_arbiter
4block            fb0        mapper              ptmx    snd       tty16  tty29  tty41  tty54  ttyS0    vcs2   vhci
5bsg              fd         mcelog              pts     sr0       tty17  tty3   tty42  tty55  ttyS1    vcs3   vhost-net
6btrfs-control    fd0        mem                 random  stderr    tty18  tty30  tty43  tty56  ttyS2    vcs4   vmci
7bus              full       midi                raw     stdin     tty19  tty31  tty44  tty57  ttyS3    vcs5   vsock
8cdrom            fuse       mqueue              rtc     stdout    tty2   tty32  tty45  tty58  uhid     vcs6   zero
9char             hidraw0    net                 rtc0    tty       tty20  tty33  tty46  tty59  uinput   vcsa
10console          hpet       network_latency     sda     tty0      tty21  tty34  tty47  tty6   urandom  vcsa1
11core             hugepages  network_throughput  sda1    tty1      tty22  tty35  tty48  tty60  usbmon0  vcsa2
12cpu              hwrng      null                sda2    tty10     tty23  tty36  tty49  tty61  usbmon1  vcsa3
13cpu_dma_latency  initctl    nvram               sda3    tty11     tty24  tty37  tty5   tty62  usbmon2  vcsa4
14crash            input      oldmem              sg0     tty12     tty25  tty38  tty50  tty63  usbmon3  vcsa5
15disk             kmsg       parport0            sg1     tty13     tty26  tty39  tty51  tty7   usbmon4  vcsa6

/etc/文件夹是系统的配置文件所在的位置。

1[root@lhy ~]# ls /etc/sysconfig/network-scripts/ifcfg-ens33
2/etc/sysconfig/network-scripts/ifcfg-ens33
3[root@lhy ~]# ls /etc/ssh/sshd_config 
4/etc/ssh/sshd_config
5[root@lhy ~]# ls /etc/
6adjtime                  ethertypes          ld.so.conf                popt.d          skel
7aide.conf                exports             ld.so.conf.d              postfix         ssh
8aliases                  favicon.png         libaudit.conf             ppp             ssl
9aliases.db               filesystems         libnl                     prelink.conf.d  statetab
10alternatives             firewalld           libuser.conf              printcap        statetab.d
11anacrontab               fstab               locale.conf               profile         subgid
12asound.conf              fuse.conf           localtime                 profile.d       subuid
13audisp                   gcrypt              login.defs                protocols       sudo.conf
14audit                    GeoIP.conf          logrotate.conf            python          sudoers
15bash_completion.d        GeoIP.conf.default  logrotate.d               rc0.d           sudoers.d
16bashrc                   gnupg               machine-id                rc1.d           sudo-ldap.conf
17binfmt.d                 GREP_COLORS         magic                     rc2.d           sysconfig
18centos-release           groff               makedumpfile.conf.sample  rc3.d           sysctl.conf
19centos-release-upstream  group               man_db.conf               rc4.d           sysctl.d
20chkconfig.d              group-              mke2fs.conf               rc5.d           systemd
21cron.d                   grub2.cfg           modprobe.d                rc6.d           system-release
22cron.daily               grub.d              modules-load.d            rc.d            system-release-cpe
23cron.deny                gshadow             motd                      rc.local        terminfo
24cron.hourly              gshadow-            mtab                      redhat-release  tmpfiles.d
25cron.monthly             gss                 my.cnf                    resolv.conf     tuned
26crontab                  host.conf           my.cnf.d                  rpc             udev
27cron.weekly              hostname            NetworkManager            rpm             vconsole.conf
28crypttab                 hosts               networks                  rsyslog.conf    vimrc
29csh.cshrc                hosts.allow         nsswitch.conf             rsyslog.d       virc
30csh.login                hosts.deny          nsswitch.conf.bak         rwtab           vmware-tools
31dbus-1                   init.d              openldap                  rwtab.d         wpa_supplicant
32default                  inittab             opt                       sasl2           X11
33depmod.d                 inputrc             os-release                securetty       xdg
34dhcp                     iproute2            pam.d                     security        xinetd.d
35DIR_COLORS               issue               passwd                    selinux         xml
36DIR_COLORS.256color      issue.net           passwd-                   services        yum
37DIR_COLORS.lightbgcolor  kdump.conf          pkcs11                    sestatus.conf   yum.conf
38dracut.conf              kernel              pki                       sgml            yum.repos.d
39dracut.conf.d            krb5.conf           plymouth                  shadow
40e2fsck.conf              krb5.conf.d         pm                        shadow-
41environment              ld.so.cache         polkit-1                  shells
42

/home/是用户的家目录，存用户的文件，类比于/root/

1[root@lhy ~]# ls /home/
2lhy01

/lib/ /lib64/等文件夹存的是库文件。库文件类似于Windows下的×.dll文件。可以用ldd命令查看某个命令的依赖库。

1[root@lhy ~]# ldd /bin/ls
2	linux-vdso.so.1 =>  (0x00007ffd4e88f000)
3	libselinux.so.1 => /lib64/libselinux.so.1 (0x00007feffcfcf000)
4	libcap.so.2 => /lib64/libcap.so.2 (0x00007feffcdca000)
5	libacl.so.1 => /lib64/libacl.so.1 (0x00007feffcbc0000)
6	libc.so.6 => /lib64/libc.so.6 (0x00007feffc7fd000)
7	libpcre.so.1 => /lib64/libpcre.so.1 (0x00007feffc59b000)
8	libdl.so.2 => /lib64/libdl.so.2 (0x00007feffc396000)
9	/lib64/ld-linux-x86-64.so.2 (0x00005636e812b000)
10	libattr.so.1 => /lib64/libattr.so.1 (0x00007feffc191000)
11	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007feffbf75000)

CentOS7之后，CentOS操作系统就没有32位系统了。32位和64位系统的最大的区别就在于识别的内存大小不一样。如果是32位的系统，只能识别4GB内存，由于操作系统本身内存占用以及地址保留，实际可以使用的内存空间为3.2G左右。

/media/目录是媒介目录，默认是空的。如果插入优盘、硬盘，系统会自动挂载到/media目录。

/mnt/是挂载目录 ，默认也为空，可以把想要的文件系统挂载到此处。

/opt/默认也是空目录，是按完系统后你又需要安装其他的应用软件，一般是源码包的软件，可以自己指定路径，管理员习惯性的把软件按在这，你也可以安装在其他位置。

/proc/存放的是进程文件，每一个进程都有一个目录，文件夹名为PID

1[root@lhy ~]# ls /proc/
21     16    265   291  304  319  332  346   399   55   641  acpi         filesystems  mdstat        softirqs
310    17    267   292  305  32   333  347   40    56   642  asound       fs           meminfo       stat
411    18    268   293  306  320  334  3535  400   57   644  buddyinfo    interrupts   misc          swaps
5111   1805  27    294  307  321  335  372   401   580  645  bus          iomem        modules       sys
612    2     272   295  308  322  336  373   4018  581  647  cgroups      ioports      mounts        sysrq-trigger
71202  20    273   296  309  323  337  380   41    582  653  cmdline      irq          mpt           sysvipc
81203  21    274   297  31   324  338  383   42    583  666  consoles     kallsyms     mtrr          timer_list
91204  22    2763  298  311  325  339  391   4259  584  679  cpuinfo      kcore        net           timer_stats
101269  23    28    299  312  326  34   392   43    585  7    crypto       keys         pagetypeinfo  tty
111288  24    285   3    313  327  340  393   468   586  76   devices      key-users    partitions    uptime
121293  25    287   30   314  328  341  394   470   587  77   diskstats    kmsg         sched_debug   version
1313    258   288   300  315  329  342  395   491   610  8    dma          kpagecount   schedstat     vmallocinfo
141346  260   289   301  316  33   343  396   5     634  9    driver       kpageflags   scsi          vmstat
1515    263   29    302  317  330  344  397   51    636  969  execdomains  loadavg      self          zoneinfo
161525  264   290   303  318  331  345  398   53    637  970  fb           locks        slabinfo

查看某一个PID进程的文件，比如/proc/285/。其中有一个cwd，这个是进程所在的路径。比如我对于某个进程不熟悉，我就根据PID来查看这个进程是从哪执行，执行什么命令（comm文件）。

1[root@lhy ~]# ls -l /proc/285/
2ls: cannot read symbolic link /proc/285/exe: No such file or directory
3total 0
4dr-xr-xr-x. 2 root root 0 Jun  2 23:57 attr
5-rw-r--r--. 1 root root 0 Jun  2 23:57 autogroup
6-r--------. 1 root root 0 Jun  2 23:57 auxv
7-r--r--r--. 1 root root 0 Jun  2 23:57 cgroup
8--w-------. 1 root root 0 Jun  2 23:57 clear_refs
9-r--r--r--. 1 root root 0 Jun  2 23:36 cmdline
10-rw-r--r--. 1 root root 0 Jun  2 23:57 comm
11-rw-r--r--. 1 root root 0 Jun  2 23:57 coredump_filter
12-r--r--r--. 1 root root 0 Jun  2 23:57 cpuset
13lrwxrwxrwx. 1 root root 0 Jun  2 23:57 cwd -> /
14-r--------. 1 root root 0 Jun  2 23:57 environ
15lrwxrwxrwx. 1 root root 0 Jun  2 23:57 exe
16dr-x------. 2 root root 0 Jun  2 23:57 fd
17dr-x------. 2 root root 0 Jun  2 23:57 fdinfo
18-rw-r--r--. 1 root root 0 Jun  2 23:57 gid_map
19-r--------. 1 root root 0 Jun  2 23:57 io
20-r--r--r--. 1 root root 0 Jun  2 23:57 limits
21-rw-r--r--. 1 root root 0 Jun  2 23:57 loginuid
22dr-x------. 2 root root 0 Jun  2 23:57 map_files
23-r--r--r--. 1 root root 0 Jun  2 23:57 maps
24-rw-------. 1 root root 0 Jun  2 23:57 mem
25-r--r--r--. 1 root root 0 Jun  2 23:57 mountinfo
26-r--r--r--. 1 root root 0 Jun  2 23:57 mounts
27-r--------. 1 root root 0 Jun  2 23:57 mountstats
28dr-xr-xr-x. 5 root root 0 Jun  2 23:57 net
29dr-x--x--x. 2 root root 0 Jun  2 23:57 ns
30-r--r--r--. 1 root root 0 Jun  2 23:57 numa_maps
31-rw-r--r--. 1 root root 0 Jun  2 23:57 oom_adj
32-r--r--r--. 1 root root 0 Jun  2 23:57 oom_score
33-rw-r--r--. 1 root root 0 Jun  2 23:57 oom_score_adj
34-r--r--r--. 1 root root 0 Jun  2 23:57 pagemap
35-r--r--r--. 1 root root 0 Jun  2 23:57 personality
36-rw-r--r--. 1 root root 0 Jun  2 23:57 projid_map
37lrwxrwxrwx. 1 root root 0 Jun  2 23:57 root -> /
38-rw-r--r--. 1 root root 0 Jun  2 23:57 sched
39-r--r--r--. 1 root root 0 Jun  2 23:57 schedstat
40-r--r--r--. 1 root root 0 Jun  2 23:57 sessionid
41-rw-r--r--. 1 root root 0 Jun  2 23:57 setgroups
42-r--r--r--. 1 root root 0 Jun  2 23:57 smaps
43-r--r--r--. 1 root root 0 Jun  2 23:57 stack
44-r--r--r--. 1 root root 0 Jun  2 23:57 stat
45-r--r--r--. 1 root root 0 Jun  2 23:57 statm
46-r--r--r--. 1 root root 0 Jun  2 23:36 status
47-r--r--r--. 1 root root 0 Jun  2 23:57 syscall
48dr-xr-xr-x. 3 root root 0 Jun  2 23:57 task
49-r--r--r--. 1 root root 0 Jun  2 23:57 timers
50-rw-r--r--. 1 root root 0 Jun  2 23:57 uid_map
51-r--r--r--. 1 root root 0 Jun  2 23:57 wchan

/run/是进程产生的临时文件，关机就会消失。

1[root@lhy ~]# ls /run/
2auditd.pid  cron.reboot  firewalld  log        NetworkManager  setrans   syslogd.pid  tuned  utmp
3console     dbus         initramfs  mount      plymouth        sshd.pid  systemd      udev   vmware
4crond.pid   faillock     lock       netreport  sepermit        sudo      tmpfiles.d   user   xtables.lock

/srv/文件夹默认是空的，存系统服务产生的一些文件。

/sys/存系统内核相关的文件，一般我们不去修改它们。

/tmp/是临时文件夹，任何用户都可以向其中添加文件，权限宽泛，但是普通用户之间的文件自己管理，有特殊权限，之后会讲。

/usr/是系统用户的目录，类似于根目录。

/var/目录存储的日志文件。比如系统日志存在/var/log/messages里面。

2.3 ls命令

ls命令可以列出当前目录的文件和文件夹，这是一个非常常用的一个命令，下面会介绍一下其常用参数。

列出文件的详细信息，使用参数-l

1[root@lhy ~]# ls -l
2total 4
3-rw-------. 1 root root 1622 May 29 14:05 anaconda-ks.cfg
4drwxr-xr-x. 2 root root   40 May 29 14:04 openscap_data

第一列是文件类型与权限，第二列表示有多少文件使用了相同的inode，inode记录的是这个文件的存储位置。inode指向的是固定的一个存储块，如果两个文件inode号相同，那么它们存储的位置就是相同的，这个和后续的硬链接有关，暂且不表。第三列表示所有者，第四列表示所属组。第五列是文件大小，单位是Byte。后面就是创建时间和文件名。

查看某一文件的inode使用-i参数。

1[root@lhy ~]# ls -i anaconda-ks.cfg 
267145602 anaconda-ks.cfg

使用-h可以更人性化的查看文件大小。

1[root@lhy ~]# ls -lh
2total 4.0K
3-rw-------. 1 root root 1.6K May 29 14:05 anaconda-ks.cfg
4drwxr-xr-x. 2 root root   40 May 29 14:04 openscap_data

使用-a可以查看所有文件，包括隐藏文件、隐藏目录。

1[root@lhy ~]# ls -la
2total 36
3dr-xr-x---.  4 root root  184 Jun  1 11:53 .
4dr-xr-xr-x. 17 root root  245 May 31 15:43 ..
5-rw-------.  1 root root 1622 May 29 14:05 anaconda-ks.cfg
6-rw-------.  1 root root 3206 Jun  1 13:52 .bash_history
7-rw-r--r--.  1 root root   18 Dec 29  2013 .bash_logout
8-rw-r--r--.  1 root root  176 Dec 29  2013 .bash_profile
9-rw-r--r--.  1 root root  176 Dec 29  2013 .bashrc
10-rw-r--r--.  1 root root  100 Dec 29  2013 .cshrc
11drwxr-xr-x.  2 root root   40 May 29 14:04 openscap_data
12drwx------.  2 root root   80 May 31 16:47 .ssh
13-rw-r--r--.  1 root root  129 Dec 29  2013 .tcshrc
14-rw-------.  1 root root 6877 Jun  1 11:53 .viminfo

每个目录下面都会有两个目录叫做当前目录（./）上一级目录（../），下面显示的就是为什么/root/的inode是4，因为有四个相同的目录指向同一个位置。一般来说对于目录来说，这个inode的个数和其下子目录数相同。

1[root@lhy ~]# ls -i /root/
2 67145602 anaconda-ks.cfg  101110119 openscap_data
3[root@lhy ~]# ls -i .
4 67145602 anaconda-ks.cfg  101110119 openscap_data
5[root@lhy ~]# ls -i .ssh/..
6 67145602 anaconda-ks.cfg  101110119 openscap_data
7[root@lhy ~]# ls -i openscap_data/..
8 67145602 anaconda-ks.cfg  101110119 openscap_data
9
10
11[root@lhy ~]# ls -ld /root
12dr-xr-x---. 4 root root 184 Jun  1 11:53 /root
13[root@lhy ~]# ls -a /root
14.   anaconda-ks.cfg  .bash_logout   .bashrc  openscap_data  .tcshrc
15..  .bash_history    .bash_profile  .cshrc   .ssh           .viminfo

使用-t选项可以按照时间降序排列。

1[root@lhy ~]# ls -lt ..
2total 20
3drwxrwxrwt.  11 root root 4096 Jun  3 03:10 tmp
4drwxr-xr-x.  22 root root  580 Jun  2 23:55 run
5drwxr-xr-x.   3 root root   19 Jun  2 23:49 home
6drwxr-xr-x.  76 root root 8192 Jun  2 23:49 etc
7drwxr-xr-x.  19 root root 3260 Jun  2 23:36 dev
8dr-xr-xr-x.  13 root root    0 Jun  2 23:36 sys
9dr-xr-xr-x. 178 root root    0 Jun  2 23:36 proc
10dr-xr-x---.   4 root root  184 Jun  1 11:53 root
11dr-xr-xr-x.   5 root root 4096 May 29 14:21 boot
12drwxr-xr-x.  19 root root  267 May 29 14:21 var
13drwxr-xr-x.  13 root root  155 May 29 14:01 usr
14lrwxrwxrwx.   1 root root    9 May 29 14:01 lib64 -> usr/lib64
15lrwxrwxrwx.   1 root root    8 May 29 14:01 sbin -> usr/sbin
16lrwxrwxrwx.   1 root root    7 May 29 14:01 lib -> usr/lib
17lrwxrwxrwx.   1 root root    7 May 29 14:01 bin -> usr/bin
18drwxr-xr-x.   2 root root    6 Nov  5  2016 media
19drwxr-xr-x.   2 root root    6 Nov  5  2016 mnt
20drwxr-xr-x.   2 root root    6 Nov  5  2016 opt
21drwxr-xr-x.   2 root root    6 Nov  5  2016 srv