This is part of the Semicolon&Sons Code Diary - consisting of lessons learned on the job. You're in the unix category.
Last Updated: 2024-04-19
In UNIX, all files in the system are organized into a single directory tree
structure with root / (as opposed to Windows, where you have a separate
directory tree for each drive - e.g. "C:", "E:)
The root / corresponds to the top directory on the main drive/partition. Any
other directory and file in the system can be reached from the root, by walking
down sub-directories.
How can you make other drives/partitions visible on unix? You mount them: mounting a drive/partition on a directory (e.g., /media/usb) means that the top directory on that drive/partition becomes visible as the directory being mounted. So, if I insert a USB stick in Windows I get a new drive, e.g., F:; if in Linux I mount it on directory /media/usb, then the top directory on the USB stick (what I would see by opening the F: drive in Windows) will be visible in Linux as directory /media/usb. In this case, the /media/usb directory is called a "mount point".
In general you can mount not only actual storage devices but also representations of anything that can be accessed as files.
A list of examples:
/proc (every Linux system does this)/var/log)Let's say it's 1999 and you want to access files on a CD-ROM. You must mount the CD-ROM on a location in the directory tree (this may be done automatically when you insert the CD). Let's say the CD-ROM device is /dev/cdrom and the chosen mount point is /media/cdrom. The corresponding command is
$ mount /dev/cdrom /media/cdrom
# i.e. mount source_file_or_device folder_where_accessible
When you are done, you can unmount with the following
$ umount /dev/cdrom
# or
$ umount /media/cdrom
# i.e. both the device name and the mount point are valid arguments
# macos
$ mount
# linux
$ mount -l
I get the following output on my mac:
# macOS Catalina mounts the read-only system volume at /.
/dev/disk1s5 on / (apfs, local, read-only, journaled)
devfs on /dev (devfs, local, nobrowse)
# The read-write data volume is here. This seems to correspond to where I, in user-space, usually work (but I'm not sure)
/dev/disk1s1 on /System/Volumes/Data (apfs, local, journaled, nobrowse)
/dev/disk1s4 on /private/var/vm (apfs, local, journaled, nobrowse)
map auto_home on /System/Volumes/Data/home (autofs, automounted, nobrowse)
/Users/jack/Library/Application Support/Google/Android File Transfer/Android File Transfer Agent.app on /private/var/folders/25/f__zt0z94vl3t812lw8zxdhw0000gn/T/AppTranslocation/EFFC1396-76BD-4D96-9575-0AD82D6DC1DA (nullfs, local, nodev, nosuid, read-only, nobrowse, mounted by jack)
# on macos
# I have a 500G drive FYI
$ df -h
Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
/dev/disk1s5 466Gi 10Gi 179Gi 6% 484398 4881968482 0% /
devfs 340Ki 340Ki 0Bi 100% 1176 0 100% /dev
/dev/disk1s1 466Gi 273Gi 179Gi 61% 3700657 4878752223 0% /System/Volumes/Data
/dev/disk1s4 466Gi 3.0Gi 179Gi 2% 4 4882452876 0% /private/var/vm
map auto_home 0Bi 0Bi 0Bi 100% 0 0 100% /System/Volumes/Data/home
/Users/jack/Library/Application Support/Google/Android File Transfer/Android File Transfer Agent.app 466Gi 263Gi 191Gi 58% 3625407 4878827473 0% /private/var/folders/25/f__zt0z94vl3t812lw8zxdhw0000gn/T/AppTranslocation/EFFC1396-76BD-4D96-9575-0AD82D6DC1DA