[SOLVED] Remounting as read-write a directory on device

dorsio · 08-10-2014, 02:43 PM

How to remount as read-write a target directory on device? (one folder) I need to replace file, which is in "Read-only file system", not allow to change permissions. Path to folder: /etc/foo/bar. I need to remount /bar folder. Embedded Linux (busybox), Linux version 2.6.18_pro500

I tried the following, with no success:

Code:

<root@elocal:/etc/foo/bar> ls -la
total 6
drwxr-xr-x    2 root     0               98 Jan 18  2011 .
drwxrwxr-x    7 root     0              105 Feb 10  2011 ..
-rw-r--r--    1 root     0             1052 Jan 18  2011 file1
-rw-r--r--    1 root     0              270 Jan 18  2011 file2
-rw-r--r--    1 root     0             1088 Jan 18  2011 file3
-rw-r--r--    1 root     0              270 Jan 18  2011 file4

mount -o rw,remount /etc/foo/bar
mount: can't find /etc/foo/bar in /proc/mounts

output mount command:

Code:

mount
rootfs on / type rootfs (rw)
/dev/root on / type squashfs (ro)
proc on /proc type proc (rw)
ramfs on /var type ramfs (rw)
sysfs on /sys type sysfs (rw)
tmpfs on /dev type tmpfs (rw)
devpts on /dev/pts type devpts (rw)
/dev/mtdblock4 on /nvram type jffs2 (rw)

output of cat /proc/mounts

Code:

cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root / squashfs ro 0 0
proc /proc proc rw 0 0
ramfs /var ramfs rw 0 0
sysfs /sys sysfs rw 0 0
tmpfs /dev tmpfs rw 0 0
devpts /dev/pts devpts rw 0 0
/dev/mtdblock4 /nvram jffs2 rw 0 0

T3RM1NVT0R · 08-10-2014, 03:09 PM

From the output you have shared I don't see any filesystem mounted on /bar. You don't mount directory, you mount filesystem on a directory. Also, the command that you have tried (though it will not work in this case as I don't see any filesystem mount on /bar) is incorrect. Correct syntax is:

Code:

mount -o remount,rw /filesystem

From what I can gather from your post you are trying to edit a file and you are unable to do so as it says read only file. I would suggest checking file permission as well as attributes using:

1. ls -al filename_or_directory_name
2. lsattr filename

dorsio · 08-10-2014, 03:26 PM

File attributes specified in my sample code Nr 1 (-rw-r--r--)

you mean this
mount -o remount,rw /squashfs

T3RM1NVT0R · 08-10-2014, 03:28 PM

Run lsattr against any of these file and paste the output. Syntax: lsattr <filename>

rknichols · 08-10-2014, 04:27 PM

Is "squashfs" the filesystem type? squashfs is inherently read-only. To make changes, you would need to install squashfs-tools, then unpack the filesystem (unsquashfs) into a directory tree somewhere writeable, make your changes, and mksquashfs a new filesystem.

More generally, while you can bind-mount a directory to a new mount point, you cannot gain any features that were not in the original mount. If the filesystem is mounted read-only, the bind-mount will also be read-only. See the "--bind" option in the mount command.

dorsio · 08-10-2014, 05:03 PM

Thanks for clarifying.