AutoFS not working as expected with CIFS shares

Question

I have this setup

Client: Centos 7.6.1810 up to date

Server: Windows 7 pro

AutoFS Configuration

# tail -1 /etc/auto.master
/srv/xray   /etc/auto.xray

# cat /etc/auto.xray
cdm8240  -fstype=cifs,ro,vers=2.0,credentials=/etc/auto.smb.cdm8-240.credentials  ://my.server/share/

# cat /etc/auto.smb.cdm8-240.credentials
username=mylogin
password=passpass123

if I mount this share manually, everything is fine

# mount.cifs -o ro,vers=2.0,credentials=/etc/auto.smb.cdm8-240.credentials //my.server/share/ /srv/xray/

# ls -l /srv/xray/ | wc -l
34
# umount /srv/xray/

If I try with autofs, I have this wrong mount entry.

/etc/auto.xray on /srv/xray type autofs (rw,relatime,fd=17,pgrp=71348,timeout=300,minproto=5,maxproto=5,indirect,pipe_ino=404555)

Then I tried to pre-create the mount point cdm8240 in the /srv/xray/ folder...

# ls -ld /srv/xray/cdm8240/
drwxrwxrwx 2 root root 6 Jun  6 08:17 /srv/xray/cdm8240/

...reload autofs and access the share and it works

# systemctl restart autofs
# ls -l /srv/xray/cdm8240/ | wc -l
34

But now here is the weird part, if I restart autofs, it dismounts the share and remove the cdm8240 folder!

# systemctl restart autofs
# find /srv/xray/ -ls
406293    0 drwxr-xr-x   2 root     root            0 Jun  6 08:20 /srv/xray/

And even changing the perms on /srv/xray/, leaving it with 755 instead of the 777 it has before! And I come back to the first situation and it's wrong mount entry.

Update 1

Tried with the "direct" mode and it looks fine now

# tail -1 /etc/auto.master
/-   /etc/auto.xray

# cat /etc/auto.xray 
/test/cdm8240  -fstype=cifs,ro,credentials=/etc/.cdm8240cred,vers=2.1,file_mode=0775,dir_mode=0775,users  ://my.server/share

so, is it a bug in the indirect mode or something "normal"?

Update 2 As explained bellow, everything was fine. I added --ghost option in my auto.master file as follow

/srv/autofs/xray   /etc/auto.xray --ghost

now the share is displayed and everything is working fine.

Answer 1

That looks perfectly normal.

The automounter takes over the top level directory, /srv/xray for all the mounts defined in the corresponding file or program, /etc/auto.xray. (In your case it's a normal file.)

Filesystems are only mounted on demand, so when you looked inside /srv/xray you would initially have seen nothing. But when you ran ls -ld /srv/xray/cdm8240/ the automounter saw the reference to the mapped directory cmd8240 and mounted the corresponding filesystem at /srv/xray/cdm8240 for you.

At some point in the future, once you'd stopped accessing the filesystem mounted at /srv/xray/cdm8240 the automounter would unmount it and /srv/xray would appear to be empty once more.

---

What I personally find helpful is to run the automounter underneath /var/autofs, so that for a mapping file auto.misc I'd have /var/autofs/misc and for an entry remote in that auto.misc file I'd have /var/autofs/misc/remote.

I then create a top-level directory /autofs and symlink directories from /var/autofs/misc/. This way they're visible to me even when not mounted, and I never need to worry about the /var/autofs/misc directory tree again.

mkdir -p -m755 /autofs
cd /autofs
ln -s ../var/autofs/misc/remote    # Create link to automounted 'remote'