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Hi I'm trying to detect ro filesystem mainly for root partition
This is portable system using usb as OS disk
The state is readonly, I cannot write anything

touch /tmp
touch: setting times of '/tmp': Read-only file system

lsblk output

lsblk /dev/sdb

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sdb      8:16   1 28.7G  0 disk 
├─sdb1   8:17   1  512M  0 part /boot/efi
└─sdb2   8:18   1 15.5G  0 part /

This is the json output

{
  "blockdevices": [
    {
      "name": "sdb",
      "kname": "sdb",
      "path": "/dev/sdb",
      "maj:min": "8:16",
      "fsavail": null,
      "fssize": null,
      "fstype": null,
      "fsused": null,
      "fsuse%": null,
      "fsver": null,
      "mountpoint": null,
      "label": null,
      "uuid": null,
      "ptuuid": "cc59543f-1263-436b-b654-441947b5d432",
      "pttype": "gpt",
      "parttype": null,
      "parttypename": null,
      "partlabel": null,
      "partuuid": null,
      "partflags": null,
      "ra": 128,
      "ro": false,
      "rm": true,
      "hotplug": true,
      "model": "SanDisk_3.2Gen1",
      "serial": "0401915ccab85f2287ceb131fd353892d7ae4b148e3eff697bb2af15fdab6e26684500000000000000000000899c7a1b00827b18915581076eab2054",
      "size": "28.7G",
      "state": "running",
      "owner": "root",
      "group": "disk",
      "mode": "brw-rw----",
      "alignment": 0,
      "min-io": 512,
      "opt-io": 0,
      "phy-sec": 512,
      "log-sec": 512,
      "rota": true,
      "sched": "mq-deadline",
      "rq-size": 2,
      "type": "disk",
      "disc-aln": 0,
      "disc-gran": "0B",
      "disc-max": "0B",
      "disc-zero": false,
      "wsame": "0B",
      "wwn": null,
      "rand": true,
      "pkname": null,
      "hctl": "52:0:0:0",
      "tran": "usb",
      "subsystems": "block:scsi:usb:pci",
      "rev": "1.00",
      "vendor": " USB    ",
      "zoned": "none",
      "dax": false,
      "children": [
        {
          "name": "sdb1",
          "kname": "sdb1",
          "path": "/dev/sdb1",
          "maj:min": "8:17",
          "fsavail": "506M",
          "fssize": "511M",
          "fstype": "vfat",
          "fsused": "5M",
          "fsuse%": "1%",
          "fsver": "FAT32",
          "mountpoint": "/boot/efi",
          "label": null,
          "uuid": "6729-75FE",
          "ptuuid": "cc59543f-1263-436b-b654-441947b5d432",
          "pttype": "gpt",
          "parttype": "c12a7328-f81f-11d2-ba4b-00a0c93ec93b",
          "parttypename": "EFI System",
          "partlabel": null,
          "partuuid": "54ce8d01-e9bc-434b-9971-5d31ded28098",
          "partflags": null,
          "ra": 128,
          "ro": false,
          "rm": true,
          "hotplug": true,
          "model": null,
          "serial": null,
          "size": "512M",
          "state": null,
          "owner": "root",
          "group": "disk",
          "mode": "brw-rw----",
          "alignment": 0,
          "min-io": 512,
          "opt-io": 0,
          "phy-sec": 512,
          "log-sec": 512,
          "rota": true,
          "sched": "mq-deadline",
          "rq-size": 2,
          "type": "part",
          "disc-aln": 0,
          "disc-gran": "0B",
          "disc-max": "0B",
          "disc-zero": false,
          "wsame": "0B",
          "wwn": null,
          "rand": true,
          "pkname": "sdb",
          "hctl": null,
          "tran": null,
          "subsystems": "block:scsi:usb:pci",
          "rev": null,
          "vendor": null,
          "zoned": "none",
          "dax": false
        },
        {
          "name": "sdb2",
          "kname": "sdb2",
          "path": "/dev/sdb2",
          "maj:min": "8:18",
          "fsavail": "8.1G",
          "fssize": "15.2G",
          "fstype": "ext4",
          "fsused": "6.2G",
          "fsuse%": "41%",
          "fsver": "1.0",
          "mountpoint": "/",
          "label": null,
          "uuid": "f769a7b6-9d09-4bc7-9249-85f50d4a1c2e",
          "ptuuid": "cc59543f-1263-436b-b654-441947b5d432",
          "pttype": "gpt",
          "parttype": "0fc63daf-8483-4772-8e79-3d69d8477de4",
          "parttypename": "Linux filesystem",
          "partlabel": null,
          "partuuid": "0cf31261-d5f9-4182-894c-283bd8fb62ad",
          "partflags": null,
          "ra": 128,
          "ro": false,
          "rm": true,
          "hotplug": true,
          "model": null,
          "serial": null,
          "size": "15.5G",
          "state": null,
          "owner": "root",
          "group": "disk",
          "mode": "brw-rw----",
          "alignment": 0,
          "min-io": 512,
          "opt-io": 0,
          "phy-sec": 512,
          "log-sec": 512,
          "rota": true,
          "sched": "mq-deadline",
          "rq-size": 2,
          "type": "part",
          "disc-aln": 0,
          "disc-gran": "0B",
          "disc-max": "0B",
          "disc-zero": false,
          "wsame": "0B",
          "wwn": null,
          "rand": true,
          "pkname": "sdb",
          "hctl": null,
          "tran": null,
          "subsystems": "block:scsi:usb:pci",
          "rev": null,
          "vendor": null,
          "zoned": "none",
          "dax": false
        }
      ]
    }
  ]
}

in lsblk RO column it shown as 0
in the json format readonly also mark as false

But when check in /proc/mounts it shown as ro ( /dev/sdb2 )

cat /proc/mounts

/dev/sdb2 / ext4 ro,relatime,errors=remount-ro 0 0
/dev/sdb1 /boot/efi vfat rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro 0 0

So lsblk cannot read the correct state ?

Running from debian 11
lsblk from util-linux 2.36.1

I need the output for notification, preferably using lsblk since it has json format.

I also found that /proc/mounts sometime have strange record for non root

# correct fstab but here different disk in same mount 
# 2 of them ro , 1 of them rw
/dev/sdk1 /mnt/disk-***0G ext4 ro,noatime 0 0
/dev/sdo1 /mnt/disk-***0G ext4 ro,noatime 0 0
/dev/sdq1 /mnt/disk-***0G ext4 rw,noatime 0 0

Test on findmnt

├─/mnt/disk-***0G          /dev/sdk1  ext4          ro,noatime
│ └─/mnt/disk-***0G        /dev/sdo1  ext4          ro,noatime
│   └─/mnt/disk-***0G      /dev/sdq1  ext4          rw,noatime
│     └─/mnt/disk-***0G    /dev/sdl1  ext4          rw,noatime

Non root disk mount with UUID with this options
It's not that important to stale the OS if it is error, but need to know if it is error.

defaults,nofail,noatime,x-systemd.device-timeout=10s,errors=continue 0 0
wpsd
  • 101
  • 4
    lsblk only displays whether the device itself is read-only. As cat /proc/mounts is showing that it is read-only, it has been mounted as such via /etc/fstab, the mount command, or some other method. – Nasir Riley Aug 10 '23 at 01:06
  • I just found out /proc/mounts sometime has multiple same entry. So not quite easy to find out which one is correct – wpsd Aug 10 '23 at 08:56
  • They are both correct. lsblk shows the device as being not read-only because it isn't whereas cat /proc/mounts shows the filesystem as being read-only because it is. You said yourself in a reply to the answer below that the /etc/fstab has the option errors=remount-ro. – Nasir Riley Aug 10 '23 at 11:35
  • For root partition it only show as one, this one I can find a way to catch it. But for normal partition ( using findmnt and mount same mount target appear multiple time for different disk ). Problem with x-systemd perhaps .... – wpsd Aug 10 '23 at 12:58

1 Answers1

2

As Nasir said in the comments, the RO column in the lsblk output is about the device being read-only, not the filesystem. So if it's read only because the filesystem is mounted with the ro option lsblk won't show it, because the device itself is still read-write. lsblk can show you only the device "state":

$ lsblk -o+RO /dev/sde3
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS RO
sde3   8:67   0  10M  0 part              0

$ sudo blockdev --setro /dev/sde3


$ lsblk /dev/sde3
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sde3   8:67   0  10M  1 part

If you want to check whether the filesystem is mounted as readonly you need to check for the ro or rw mount option (conveniently mount will mount read-only devices with the ro option by default so you don't need to check both the device and filesystem). You can use findmnt to do that so for example something like

$ findmnt -n -o options /dev/sde3
ro,relatime,seclabel

$ findmnt -n -o options /dev/sde3 | grep -q ^ro && echo "read only"
read only
Vojtech Trefny
  • 18,146
  • hmm, I set the options in fstab to errors=remount-ro, since it is a flash disk sometime it get mounted to ro maybe due to some corrupt fs.

    sometime the ssh key exchange will be error under this circumstances. so I know it was flash disk problem. But sometime it's not , currently I use touch to detect it.

     – wpsd Aug 10 '23 at 08:56