Ubuntu – Chmod error changing permission read only file system

chmodpermissions

I have three main partitions on my disc /dev/sda:

/dev/sda1            2048   117186559    58592256   83  Linux
/dev/sda2       117186560   128905215     5859328   82  Linux swap / Solaris
/dev/sda3   *   128905216   324216831    97655808    7  HPFS/NTFS/exFAT
/dev/sda4       324216832  1250263039   463023104    b  W95 FAT32

/dev/sda3 is a Windows 7 partition and /dev/sda4 is a FAT32 partition where I keep my data. My problem is that yesterday I can't write on /dev/sda4 and when I tried to change the file permissions I get an error:

$ sudo chmod 777 /media/fourat/74A7-A44E/
chmod: changing permissions of ‘74A7-A44E/’: Read-only file system

mount output:

/dev/sda1 on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/cgroup type tmpfs (rw)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755)
none on /sys/fs/pstore type pstore (rw)
systemd on /sys/fs/cgroup/systemd type cgroup (rw,noexec,nosuid,nodev,none,name=systemd)
gvfsd-fuse on /run/user/1000/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=fourat)
/dev/sda4 on /media/fourat/74A7-A44E type vfat (rw,nosuid,nodev,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2)

Solved: Remounted the partition as instructed in mikewhatever's comment with

sudo mount -o remount,rw /dev/sda4

Best Answer

I guess you can use the below command to remount:

adb remount

this solution should work for the above issue

Related Solutions

Ubuntu – Can’t change permission of folders: read-only file system error

You will need to have credentials to enable write access. If you do not have the ability, then this is a moot point. If you have the ability enable it and change the file permissions.

Ubuntu – ‘chmod -644’ would set file permission to 000

You are using -664, just use 664 instead. And never use sudo when you dont need to. If that's your file, you don't need sudo:

chmod 644 my_file

When you run chmod with a - before the mode, you will remove that mode. See man chmod (emphasis mine):

The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected.

The numbers are:

1: execute
2: write
4: read

So a file with 777 permissions means everyone has the right to do all three, since 1 + 2 + 4 = 7, and therefore setting the permissions to 7 means allowing read, write and execute.

If you start with a file whose mode is 777:

$ ls -l my_file 
-rwxrwxrwx 1 terdon terdon 0 May 28 13:45 my_file

And now run chmod -644, you will remove the bits 644, and end up with a file whose mode is 133:

$ chmod -644 my_file; ls -l my_file 
---x-wx-wx 1 terdon terdon 0 May 28 13:45 my_file

That's because you removed 6 (read (4) + write (2)) from the owner's permissions, leaving only 1 (execute) set, and 4 (read) from the group and other permissions. The result is a file with only execute (1) permissions for the owner, and write and execute (you unset 4, leaving 1 and 3) permissions for the rest.

Because your file presumably had the default permissions for new files, so 644, when you ran chmod -644 my_file, you removed all of the set permission bits and got a file with no permissions for anybody.

$ ls -l my_file 
-rw-r--r-- 1 terdon terdon 0 May 28 13:45 my_file
$ chmod -644 my_file
$ ls -l my_file 
---------- 1 terdon terdon 0 May 28 13:45 my_file

Best Answer

Related Solutions

Ubuntu – Can’t change permission of folders: read-only file system error

Ubuntu – ‘chmod -644’ would set file permission to 000

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