Ubuntu /dev/loop＜0..n＞挂载的目录的分析

执行命令df -h 

lkmao@ubuntu:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            1.6G     0  1.6G   0% /dev
tmpfs           391M  2.1M  389M   1% /run
/dev/sda1        59G   30G   26G  54% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/loop0       13M   13M     0 100% /snap/gnome-characters/139
/dev/loop1      2.3M  2.3M     0 100% /snap/gnome-calculator/260
/dev/loop2      3.8M  3.8M     0 100% /snap/gnome-system-monitor/57
/dev/loop3       91M   91M     0 100% /snap/core/6350
/dev/loop4       15M   15M     0 100% /snap/gnome-logs/45
/dev/loop5      141M  141M     0 100% /snap/gnome-3-26-1604/74
/dev/loop6       35M   35M     0 100% /snap/gtk-common-themes/818
tmpfs           391M   16K  391M   1% /run/user/121
tmpfs           391M   24K  391M   1% /run/user/1000
lkmao@ubuntu:~$ 

他们都是挂载到/snap目录下：

lkmao@ubuntu:/snap$ ls
bin   gnome-3-26-1604   gnome-characters  gnome-system-monitor  README
core  gnome-calculator  gnome-logs        gtk-common-themes
lkmao@ubuntu:/snap$ 

 查看README文件：

lkmao@ubuntu:/snap$ cat README 

This directory presents installed snap packages.

It has the following structure:

/snap/bin                   - Symlinks to snap applications.
/snap/<snapname>/<revision> - Mountpoint for snap content.
/snap/<snapname>/current    - Symlink to current revision, if enabled.

DISK SPACE USAGE

The disk space consumed by the content under this directory is
minimal as the real snap content never leaves the .snap file.
Snaps are *mounted* rather than unpacked.

For further details please visit
https://forum.snapcraft.io/t/the-snap-directory/2817
lkmao@ubuntu:/snap$ 

查看bin目录下的文件：如下所示，这不是不是很想busybox的套路。

lkmao@ubuntu:/snap/bin$ ls -lsh
total 0
0 lrwxrwxrwx 1 root root 13 Jul 25 22:49 gnome-calculator -> /usr/bin/snap
0 lrwxrwxrwx 1 root root 13 Jul 25 22:49 gnome-characters -> /usr/bin/snap
0 lrwxrwxrwx 1 root root 13 Jul 25 22:49 gnome-logs -> /usr/bin/snap
0 lrwxrwxrwx 1 root root 13 Jul 25 22:49 gnome-system-monitor -> /usr/bin/snap
lkmao@ubuntu:/snap/bin$

 如果没猜错，PATH环境变量中很定有/snap/bin这个目录：打印PATH如下所示：

lkmao@ubuntu:/snap/bin$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
lkmao@ubuntu:/snap/bin$

/dev/loop0 挂载到 /snap/gnome-characters/139，看名字gnome-characters好像是一个软件，执行

gnome-characters

执行结果如下，看起来是个很有趣而且没什么用的的软件。 所以不能删。

 计算器：gnome-calculator

 系统监控：gnome-system-monitor

 

日志浏览工具：gnome-logs 

其他的三个目录

 /snap/core/6350目录的文件，这不就是一个根文件系统吗

lkmao@ubuntu:/snap/core/6350$ ls
bin   dev  home  lib64  meta  opt   root  sbin  srv  tmp  var
boot  etc  lib   media  mnt   proc  run   snap  sys  usr  writable
lkmao@ubuntu:/snap/core/6350$ 

 cd /snap/gnome-3-26-1604/74，这个目录，嗯？

lkmao@ubuntu:/snap/gnome-3-26-1604/74$ ls
etc  lib  meta  sbin  snap  usr  var
lkmao@ubuntu:/snap/gnome-3-26-1604/74$ 

lkmao@ubuntu:/snap/gnome-3-26-1604/74/etc$ cd /snap/gtk-common-themes/818
lkmao@ubuntu:/snap/gtk-common-themes/818$ ls
meta  share  snap
lkmao@ubuntu:/snap/gtk-common-themes/818$ tree -L 2
.
├── meta
│   └── snap.yaml
├── share
│   ├── gtk2
│   ├── icons
│   ├── sounds
│   └── themes
└── snap
    ├── manifest.yaml
    └── snapcraft.yaml

7 directories, 3 files
lkmao@ubuntu:/snap/gtk-common-themes/818$