09-09-2003
Linux questions
Hi everyone,
I came from a diffrent UNIX background and am trying to learn Linux (Red Hat) in a hurry. I would be very grateful if you could help me with the following questions. I know the answers for questions 1, 3, and 4 in a Sun Solaris environment, but not in Linux... Thanks in advance for your help!
1. When the command "touch" is used to create a file, it assigns some default permissions to the file. What would you do to make "touch" command create files with different default permissions?
2. Using bash shell, run the following commands in a clean directory:
for ((i=20000;i--;)) ; do touch test$i ; done
for ((i=10;i--;)) ; do touch file$i ; done
This will take a while.
Now try to list all files beginning with 'test':
ls test*
This will give an error:
bash: /bin/ls: Argument list too long
How would you get around this problem (i.e., successfully list all these files)?
3. How would you automatically mount a device each time the system starts up?
4. While trying to "umount" a device, it will fail if the device is busy. How would you determine which process is causing the device to be busy?
-- Enigma777
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LEARN ABOUT REDHAT
umount
UMOUNT(8) Linux Programmer's Manual UMOUNT(8)
NAME
umount - unmount file systems
SYNOPSIS
umount [-hV]
umount -a [-dflnrv] [-t vfstype] [-O options]
umount [-dflnrv] dir | device [...]
DESCRIPTION
The umount command detaches the file system(s) mentioned from the file hierarchy. A file system is specified by giving the directory where
it has been mounted. Giving the special device on which the file system lives may also work, but is obsolete, mainly because it will fail
in case this device was mounted on more than one directory.
Note that a file system cannot be unmounted when it is `busy' - for example, when there are open files on it, or when some process has its
working directory there, or when a swap file on it is in use. The offending process could even be umount itself - it opens libc, and libc
in its turn may open for example locale files. A lazy unmount avoids this problem.
Options for the umount command:
-V Print version and exit.
-h Print help message and exit.
-v Verbose mode.
-n Unmount without writing in /etc/mtab.
-r In case unmounting fails, try to remount read-only.
-d In case the unmounted device was a loop device, also free this loop device.
-a All of the file systems described in /etc/mtab are unmounted. (With umount version 2.7 and later: the proc filesystem is not
unmounted.)
-t vfstype
Indicate that the actions should only be taken on file systems of the specified type. More than one type may be specified in a
comma separated list. The list of file system types can be prefixed with no to specify the file system types on which no action
should be taken.
-O options
Indicate that the actions should only be taken on file systems with the specified options in /etc/fstab. More than one option type
may be specified in a comma separated list. Each option can be prefixed with no to specify options for which no action should be
taken.
-f Force unmount (in case of an unreachable NFS system). (Requires kernel 2.1.116 or later.)
-l Lazy unmount. Detach the filesystem from the filesystem hierarchy now, and cleanup all references to the filesystem as soon as it is
not busy anymore. (Requires kernel 2.4.11 or later.)
THE LOOP DEVICE
The umount command will free the loop device (if any) associated with the mount, in case it finds the option `loop=...' in /etc/mtab, or
when the -d option was given. Any pending loop devices can be freed using `losetup -d', see losetup(8).
FILES
/etc/mtab table of mounted file systems
SEE ALSO
umount(2), mount(8), losetup(8).
HISTORY
A umount command appeared in Version 6 AT&T UNIX.
Linux 2.0 26 July 1997 UMOUNT(8)