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I'm running slackware 14.0 linux.

I was recently doing an open office document and sent emails out and then my internet was cutting out then after a bit I got hinted that my disk was full then I cleared up some space. But what I don't understand is how is it possible that I can use my computer with the root filesystem mounted but it doesn't automatically show it with the mount command?

Here is an extract when I execute dmesg while looking for info about the root partition (sda2):

[    4.293905] sd 2:0:0:0: [sda] 234441648 512-byte logical blocks: (120 GB/111 GiB)
[    4.294372] sd 2:0:0:0: [sda] Write Protect is off
[    4.294434] sd 2:0:0:0: [sda] Mode Sense: 00 3a 00 00
[    4.294477] sd 2:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[    4.307345]  sda: sda1 sda2 sda3 sda4
[    4.307942] sd 2:0:0:0: [sda] Attached SCSI disk
[    4.322793] EXT3-fs (sda2): mounted filesystem with ordered data mode
[    6.917851] EXT3-fs (sda2): using internal journal
[   15.260713] EXT3-fs (sda3): using internal journal
[   15.260774] EXT3-fs (sda3): mounted filesystem with ordered data mode
[   15.297340] EXT3-fs (sda4): using internal journal
[   15.297400] EXT3-fs (sda4): mounted filesystem with ordered data mode

I also ran fsck to do a thorough scan on the same partition and it found no errors.

When I ran mount, I see this but no entry for sda2:

proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
/dev/sda3 on /80gb type ext3 (rw,commit=0)
/dev/sda4 on /disk type ext3 (rw,commit=0)
/dev/sda1 on /DOS type vfat (rw,umask=0022)
tmpfs on /dev/shm type tmpfs (rw)
/dev/ram0 on /tmp type ext2 (rw,nodev,noatime,nodiratime)

So I gave it a gamble to mount it manually and I get this error:

mount: /dev/sda2 already mounted or / busy

I looked for a running utility that might have something to do with automounting with "ps -A | grep uto" but nothing was found.

I checked /etc/fstab and I see:

/dev/sda2        /                ext3        defaults         1   1
/dev/sda3        /80gb            ext3        defaults         1   2
/dev/sda4        /disk            ext3        defaults         1   2
/dev/sda1        /DOS             vfat        umask=0022       1   0
/dev/cdrom       /mnt/cdrom       auto        noauto,owner,ro,comment=x-gvfs-show 0   0
/dev/fd0         /mnt/floppy      auto        noauto,owner     0   0
devpts           /dev/pts         devpts      gid=5,mode=620   0   0
proc             /proc            proc        defaults         0   0
tmpfs            /dev/shm         tmpfs       defaults         0   0

Yet what is odd is that I can still access the filesystem even though its not listed in mount and I am able to save data to it.

Also, what's even odder is that for me to find disk space info in the root filesystem I have to execute "df -h /" instead of "df -h". then it shows "-" as the filesystem. I would rather do "df -h" and see "/dev/sda2" as the filesystem with the correct free space.

Also, when I stared at the startup sequence, it indicated that everything is mounted. Only time it would unmount things is when I restart or shutdown my computer.

How do I fix this so when I execute mount with no parameters, I see the root partition already mounted along with the other partitions?

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  • Typing "mount" won't display "/" - "/" is where everything is mounted. Type "df -h". Apr 11, 2021 at 2:21
  • @CinaedSimson I dunno, mount does show / for me (on Debian 10). It's a mountpoint, why do you think mount shouldn't show it?
    – marcelm
    Apr 11, 2021 at 16:09
  • Try "dmesg | grep EXT4-fs" and you should see filesystems on all the partitions. Root should be the one with "mounted filesystem with ordered data mode - or in your case, sda1. In fact, there should also be a "re-mounted" entry for sda1. Apr 11, 2021 at 19:20

1 Answer 1

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The mount command only shows you whatever is listed in /etc/mtab. If you want to see all the mounts, you can do cat /proc/mounts. You can mount something without having it recorded in /etc/mtab by using the mount -n option.

The fact that /etc/mtab and /proc/mounts are not necessarily the same thing can be useful for the shutdown scripts, as it lets them only worry about unmounting the stuff that's listed in /etc/mtab.

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  • Why is this still a thing in modern Linux? In the distant past, there was no /proc/mounts, so /etc/mtab was needed... Apr 11, 2021 at 12:58
  • @user253751 Probably for backwards compatibility, people might have code that depends on this behavior.
    – Garo
    Apr 11, 2021 at 14:27
  • @user253751 "Why is this still a thing in modern Linux?" - It probably varies by distribution; on my system (Debian 10), /etc/mtab is a symlink to /proc/self/mounts, so mount shows all mounts.
    – marcelm
    Apr 11, 2021 at 16:10
  • I checked /proc/mounts but I did not see /dev/sda2 listed for / but I did see rootfs listed for /. and mtab is a separate file which also does not list /dev/sda2. fstab DOES list /dev/sda2 as explained in my question.
    – Mike St
    Apr 11, 2021 at 17:41
  • @Garo: I had a bunch of stuff break when they switched /etc/mtab -> /proc/mounts. Turned out that old stuff assumed that when /etc/mtab couldn't be opened for writing that / was still readonly and /etc/mtab was untrustworthy.
    – Joshua
    Apr 11, 2021 at 18:27

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