[SOLVED] What are the Slackware Defaults for fstab

StevenXL · 01-23-2014, 04:43 PM

Hi guys,

So in my initial installation of Slackware, I mounted my Windows (NTFS) partition as read-only except for root. The fstab had the following for the NTFS partition:

/dev/sda2 /ntfs ntfs-3g fmask=133,dmask=022 1 0

And normal partitions had the following:

/dev/sda6 /home ext4 defaults 1 2

I tried to edit fstab in order to mount it read-write, and given the settings for /dev/sda6, I did the following:

/dev/sda2 /ntfs ntfs-3g defaults 1 0

However, this didn't have the intended effects. /dev/sda2 was not mounted read-write. I know how to edit the settings in order to mount it read-write, but I am wondering why changing it to defaults did not work.

What are the defaults in Slackware, and how could I have figured that out in the command line?

Thanks!

P.S., this is what I currently have in the fstab for the NTFS partition:

/dev/sda2 /ntfs ntfs-3g rw,suid,dev,exec,auto,user,async 1 0

Didier Spaier · 01-23-2014, 04:47 PM

Code:

/dev/sda2   /ntfs   ntfs-3g   fmask=111,dmask=000   1   0

FYI this is how Slackware installer set it up if you request R/W for everyone:

Code:

  dialog --backtitle "Setting permissions on NTFS partition $NEW_DIR" \
  --title "SET SECURITY FOR NTFS PARTITION $NEW_DIR" \
  --default-item "fmask=177,dmask=077" \
  --menu "Because users could go snooping through (or destroy, depending on \
the settings) your Windows partition, you should choose how much access would you \
like your non-root users to have to partition $NEW_DIR.  The access level can \
range from no access at all, to read-only for everyone, to read-write access \
for every user on the machine.  A reasonable default (read-write for root only) \
is chosen, but you may set this any way that you like." \
18 77 4 \
"fmask=177,dmask=077" "Root has read/write access, users have no access (ntfs-3g)" \
"fmask=333,dmask=222" "Everyone has read only access (built-in kernel ntfs driver)" \
"fmask=133,dmask=022" "Everyone has read access, but only root can write (ntfs-3g)" \
"fmask=111,dmask=000" "All users can read/write to any file (ntfs-3g)" \
2> $TMP/ntfs_security

PS I almost forgot: Hi, and welcome to LQ.

neymac · 01-23-2014, 05:01 PM

@Didier Spaier: my fstab uses "umask=000" for ntfs partitions. Which is the difference using user mask (umask) instead of file and directory masks (fmask and dmask)?

Didier Spaier · 01-23-2014, 05:08 PM

Quote:

Originally Posted by neymac

@Didier Spaier: my fstab uses "umask=000" for ntfs partitions. Which is the difference using user mask (umask) instead of file and directory masks (fmask and dmask)?

Here is what says man ntfs-3g:

Code:

OPTIONS
       Below is a summary of the options that ntfs-3g accepts.

       uid=value and gid=value
              Set  the  owner  and  the  group of files and directories. The values are numerical.  The
              defaults are the uid and gid of the current process.

       umask=value
              Set the  bitmask of the file and directory permissions that are not present. The value is
              given in octal. The default value is 0 which means full access to everybody.

       fmask=value
              Set  the   bitmask  of  the file permissions that are not present.  The value is given in
              octal. The default value is 0 which means full access to everybody.

       dmask=value
              Set the  bitmask of the directory permissions that are not present. The value is given in
              octal. The default value is 0 which means full access to everybody.

So somehow umask=0 is equivalent to dmask=0 and fmask=0.

Habitual · 01-23-2014, 05:22 PM

See https://www.linuxquestions.org/quest...issions-35729/
for my notes on how I fixed mine.

StevenXL · 01-23-2014, 06:30 PM

Thank you very much for all the input. (I certainly learned something new - which is my goal in switching to Slackware).

I think I might have confused people with all the information I offered.

My question is as follows:

fstab contains the following "/dev/sda6 /home ext4 defaults 1 2". What are the options set to when a user specifies that fstab should use the 'defaults' setting?

P.S. @Habitual - I like your signature.

Habitual · 01-23-2014, 07:23 PM

Quote:

Originally Posted by StevenXL

What are the options set to when a user specifies that fstab should use the 'defaults' setting?

Users don't specify anything in /etc/fstab.

You, as an administrator, can set the options for a particular user, but they themselves do not have control over it.
I'm not sure that regular users can even issue a mount without elevated privileges (an explicit directive in sudoers)...

If allowed (sudo privs) a user can mount using the -o <option> -o <option> (multiples are ok) eg:

Code:

mount -t ntfs-3g /dev/sda2 ~/Windows -o  rw -o dmask=022 -o fmask=133 0 0

assuming the user has made a ~/Windows mount point.

man ntfs-3g shows:

Code:

Access Handling and Security
       By  default,  files and directories are owned by the effective user and group of the mounting process, and everybody
       has full read, write, execution and directory browsing permissions.  You can also assign  permissions  to  a  single
       user by using the uid and/or the gid options together with the umask, or fmask and dmask options.

So for example:
as root, I check the zabbix user's ID with

Code:

id zabbix

and I get

Code:

uid=101(zabbix) gid=156(zabbix) groups=156(zabbix)

I'd instruct the user, or create a script to use

Code:

mount -t ntfs-3g /dev/sda2 ~/Windows -o  rw -o dmask=022 -o fmask=133 0 0

That should allow the <user> to mount with Read/Write privs and honor Linux file and directory permissions (files=644 and directories=755)

the uid stuff in /etc/fstab for the above user <zabbix> could be

Code:

/dev/sda2 /home/zabbix/Windows ntfs-3g  rw,uid=101,gid=156,dmask=022,fmask=133 0 0

See http://linux.die.net/man/8/ntfs-3g

I probably got some of that wrong, but fortunately, there are better people than I at explaining this stuff. (also a "we" thing)
I don't get out much and live in a terminal.

Edit: "defaults" are conservative, probably to save the system from its users?

Subscribed with interest...

StevenXL · 01-23-2014, 07:47 PM

Thank you very much for your continued response Habitual. It is all very helpful and informative. However, it is not what I am looking for, so I will try to rephrase the question for others.

Ubuntu has a page that delineates what the defaults are (https://help.ubuntu.com/community/Fstab).

Specifically, it reads: defaults = rw, suid, dev, exec, auto, nouser, and async.

What I would like to know is what are the defaults in Slackware.

What are the options being passed to mount when it finds the following line in fstab:

/dev/sda2 /ntfs ntfs-3g defaults 1 0

Thanks guys!

Habitual · 01-23-2014, 07:52 PM

Quote:

Originally Posted by StevenXL

Thank you very much for your continued response Habitual. It is all very helpful and informative. However, it is not what I am looking for, so I will try to rephrase the question for others.

and I'll butt out.

slacksam · 01-23-2014, 09:20 PM

Quote:

Originally Posted by StevenXL

What are the options being passed to mount when it finds the following line in fstab:

/dev/sda2 /ntfs ntfs-3g defaults 1 0

As you can see in the manpage for "mount", the defaults in Slackware are the same as in Ubuntu:

Code:

$ man mount
...
       defaults
              Use  default  options:  rw,  suid,  dev, exec, auto, nouser, and
              async.
...

StevenXL · 01-23-2014, 09:39 PM

@slackslam,

Thank you. I feel like a dummy. :-(

Quote:

Originally Posted by slacksam

As you can see in the manpage for "mount", the defaults in Slackware are the same as in Ubuntu:

Code:

$ man mount
...
       defaults
              Use  default  options:  rw,  suid,  dev, exec, auto, nouser, and
              async.
...