Android - What's the Android equivalent of /etc/fstab?

Don't think about Android as a heavily modified Linux distribution. Because it's not. The nearly only thing that Android shares with a Linux distribution is the kernel. And even this component is modified. Also other core components, like the libc, differ.

Android has no /etc/fstab

You don't need /etc/fstab to mount an partition. But there is IIRC no mount command either.dev_mount should work (root required). To answer your questions title: All startup system mounting is done with the/etc/vold.fstab helper script.

The fstab file is in /.

It's called /fstab.$systemname.rc where $systemname is based on the handset's fingerprint property, either identified as category of chipset or handset itself.

I realize that this is an old topic, but some of the answers here actually hindered my efforts to learn about fstab and Android because they so strongly imply that the fstab situation in Android is extremely different from other Linux distributions. From what I can tell, it isn't.

However, reading different responses here made me wonder: what fstab-equivalent file or files are on my device?

Stepping back for a moment, noting that "Android has no /etc/fstab" is probably not helpful to the OP since they must have already known this. If this were untrue, their question (asking what the Android equivalent of /etc/fstab is) would not make any sense. On the other hand, we know @Flow was not trying to imply that there was no equivalent on Android, since they mentioned one of them, a "helper script" named /etc/vold.fstab.

All in all, I think the takeaway from @Flow's post is that on some systems, there is a file (possibly a "helper script" - I can't verify that on my phone) called /etc/vold.fstab, and on those systems, this file is the nearest equivalent to /etc/fstab.

Getting back to wondering about my own device, I am going to post my findings here for several reasons, in spite of the age of the OP:

• First, I want to document all of the fstab-style files I can find on my phone, a Pixel 2XL.
• Second, I want to show people, especially Linux/Android newbies, that it is fairly easy to find these files on your own device ("teach them to fish").
• Third, it's helpful for me to write up my findings (bonus: I'll always be able to find it again here on StackExchange!).
• Finally, Google is still serving this page up so there's a chance this will help someone other than me.

So let me try to sum up everything I have learned from all of this:

Android, or at least its variants that I have access to, does make use of fstab-style files. However, the exact name, location, and function of these files vary by distribution - meaning by Android version and device, and also by ROM if you use a custom ROM.

To find these files on your system, open up a terminal emulator like tmux or adb shell and run something like this: find / -type f -iname '*fstab*' 2>/dev/null. The redirection of file 2 (stderr) to /dev/null will make your output much cleaner as you will be able to ignore the onslaught of error messages you will get from find, even if you are root.

On my system (a Pixel 2XL, code name "taimen"), I found three candidate files:

taimen:/ # find / -type f -iname '*fstab*' 2>/dev/null

/sbin/.core/mirror/vendor/etc/fstab.taimen
/vendor/etc/fstab.taimen
/data/data/com.android.omadm.service/files/dm/dmt_data/fstab

The first two are separate files in that neither is a hard or symbolic link to the other, but if you diff them you will find that they are identical. Looking a little deeper, if you run stat on the files you will see that they have the same Device and Inode values:

taimen:/ # stat /sbin/.core/mirror/vendor/etc/fstab.taimen /vendor/etc/fstab.taimen

  File: `/sbin/.core/mirror/vendor/etc/fstab.taimen'
  Size: 1326     Blocks: 16      IO Blocks: 512 regular file
Device: fc00h/64512d     Inode: 925      Links: 1
Access: (644/-rw-r--r--)        Uid: (    0/    root)   Gid: (    0/    root)
Access: 2009-01-01 02:00:00.000000000
Modify: 2009-01-01 02:00:00.000000000
Change: 2009-01-01 02:00:00.000000000

  File: `/vendor/etc/fstab.taimen'
  Size: 1326     Blocks: 16      IO Blocks: 512 regular file
Device: fc00h/64512d     Inode: 925      Links: 1
Access: (644/-rw-r--r--)        Uid: (    0/    root)   Gid: (    0/    root)
Access: 2009-01-01 02:00:00.000000000
Modify: 2009-01-01 02:00:00.000000000
Change: 2009-01-01 02:00:00.000000000

stat reports both of these filenames as regular files with only one link each (so no hard or symbolic links are involved). I'm not a filesystem expert but what has happened here is that the same device has been mounted twice. You can see this in the output of the following command, where the only differences between the two lines of output in are the mount points (the part immediately after "on"):

taimen:/ $ mount | grep vendor

/dev/block/dm-0 on /vendor type ext4 (ro,seclabel,relatime,block_validity,delalloc,barrier,user_xattr)
/dev/block/dm-0 on /sbin/.core/mirror/vendor type ext4 (ro,seclabel,relatime,block_validity,delalloc,barrier,user_xattr)

The third file is only visible to me if I login as root, so if you have a device identical to mine, you still will not find, or have access to, this file unless your phone is rooted. That file has to do with a service called Open Mobile Alliance Device Management, but that is a service I know very little about, so I will just mention it here, and you can Google for details about that if you'd like.