[disk][linux] fix readlink error which system boot by nfs mount

[arstercz]

Some host maybe boot the linux os with nfs mount, such as:

# cat /proc/self/mountinfo
14 1 0:14 / / rw,relatime - nfs /dev/root rw,vers=2,rsize=4096,wsize=4096,namlen=255,hard,nolock,proto=udp,port=65535,timeo=11,retrans=3,sec=sys,mountport=65535,addr=10.1.1.10
15 14 0:3 / /proc rw,relatime - proc /proc rw
16 15 0:13 / /proc/bus/usb rw,relatime - usbfs /proc/bus/usb rw
17 14 0:0 / /sys rw,relatime - sysfs /sys rw
18 14 0:15 / /dev rw,relatime - tmpfs none rw,mode=755
19 18 0:9 / /dev/pts rw,relatime - devpts devpts rw,gid=5,mode=620
20 14 8:0 / /export rw,relatime - xfs /dev/sda rw,noquota
21 15 0:16 / /proc/sys/fs/binfmt_misc rw,relatime - binfmt_misc none rw

and the device 0:14 can not found at this host:

# ls /sys/dev/block/ -hl
total 0
lrwxrwxrwx  1 root root 0 Apr 26 18:14 1:0 -> ../../block/ram0
lrwxrwxrwx  1 root root 0 Apr 26 18:14 1:1 -> ../../block/ram1
lrwxrwxrwx  1 root root 0 Apr 26 18:14 1:10 -> ../../block/ram10
......
lrwxrwxrwx  1 root root 0 Apr 26 18:14 7:7 -> ../../block/loop7
lrwxrwxrwx  1 root root 0 Apr 26 18:14 8:0 -> ../../block/sda
lrwxrwxrwx  1 root root 0 Apr 26 18:14 9:0 -> ../../block/md0

so we'll get the following error:

readlink /sys/dev/block/0:14: no such file or directory

this commit ignore the nfs type so that we can skip this error.

[shirou]

According to the psutil implementation, there are other ways, but they are more complicated. Could you show us following ?

• /proc/partitions
• /sys/class/block/

[arstercz]

Hi @shirou , because we compiled the(kernel-2.6.32) on an old system(centos 5(kernel-2.6.18)), so there is no dirs /sys/class/block,

# cat /proc/partitions
major minor  #blocks  name

   8        0 1468006400 sda


# ls -hl /sys/class/block
ls: /sys/class/block: No such file or directory


# ls -hl /sys/block/
total 0
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop0
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop1
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop2
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop3
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop4
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop5
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop6
drwxr-xr-x  6 root root 0 Apr 26 18:14 loop7
drwxr-xr-x  7 root root 0 Apr 26 18:14 md0
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram0
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram1
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram10
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram11
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram12
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram13
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram14
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram15
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram2
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram3
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram4
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram5
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram6
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram7
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram8
drwxr-xr-x  6 root root 0 Apr 26 18:14 ram9
drwxr-xr-x  6 root root 0 Apr 25 17:31 sda



# cat /proc/self/mountinfo
14 1 0:14 / / rw,relatime - nfs /dev/root rw,vers=2,rsize=4096,wsize=4096,namlen=255,hard,nolock,proto=udp,port=65535,timeo=11,retrans=3,sec=sys,mountport=65535,addr=10.1.1.10
15 14 0:3 / /proc rw,relatime - proc /proc rw
16 15 0:13 / /proc/bus/usb rw,relatime - usbfs /proc/bus/usb rw
17 14 0:0 / /sys rw,relatime - sysfs /sys rw
18 14 0:15 / /dev rw,relatime - tmpfs none rw,mode=755
19 18 0:9 / /dev/pts rw,relatime - devpts devpts rw,gid=5,mode=620
20 14 8:0 / /export rw,relatime - xfs /dev/sda rw,noquota
21 15 0:16 / /proc/sys/fs/binfmt_misc rw,relatime - binfmt_misc none rw


# df -hl
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda              1.4T   41G  1.4T   3% /export


# mount  -l
manager_host:/export/backup on / type nfs (rw,addr=10.1.1.10)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
usbfs on /proc/bus/usb type usbfs (rw)
/dev/sda on /export type xfs (rw) []
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)


# cat /proc/cmdline
root=/dev/nfs nfsroot=10.1.1.10:/export/backup ip=dhcp BOOT_IMAGE=pxeboot/vmlinuz.backup


# rdev
0x000e /

[shirou]

Thank you for the report. It seems we can not get a root device from those files.

According to this psutil code, use /dev/root if we can not find a root device.

So, how about change error handling on here like this?

if err == nil {
	d.Device = strings.Replace(d.Device, "root", filepath.Base(devpath), 1)
}

[arstercz]

Thanks @shirou , we should follow the psutil principles, and I test ok.

[shirou]

Thank you for your update!