- How to protect single user mode (init 1) in Red Hat linux?
- How to Kernel compile ?
- Restrict user login based on time and terminal ?
- How to Manage Write CD Images in Linux?
- Specify Download Speed / Download Rate Using wget limit-rate
- Finding total size of files owned by a particular user
- Finding all large files in the root filesystem
How to protect single user mode (init 1) in Red Hat linux?
To protect this:-
# vi /etc/inittab
#add this line
su:S:wait:/sbin/sulogin
#save and exit
#init 1
here you prompt for password.
How to Kernel compile ?
# make config
or
# make menuconfig
or
# make xconfig <– Basen on QT in 2.6.x
or
# make gconfig
# make dep
# make bzImage
copy this bzImage into /boot/ and create new initrd (mkinitrd command) file . after this modify grub.conf file then restart.
Restrict user login based on time and terminal ?
#vi /etc/security/time.conf
A simple /etc/security/time.conf file will look like:
*;tty1;jim;A10000-2300
login & ssh;*;jane | jim|bill|susan;A11200-2000
ftp;*;guest;MoTuFr0800-1700&!Wk0000-2400
finger;*;guestA10000-2400
Now, let’s examine the contents of this file. The first line:
*;tty1;jim;A10000-2300
allows the user Jim access to all services from midnight until 11:00 P.M., as long as Jim is logging from tty1.
The second line:
login & ssh;*;jane | jim|bill|susan;A11200-2000
allows the users Jane, Jim, Bill, and Susan access to the system on any day of the week from 12:00 noon until 8:00 P.M. as long as they are accessing the system using /bin/login, or the secure shell, ssh.
The third line:
ftp; *;guest;Wk0000-2400
allows the user guest access to the system via FTP at any time during the weekend.
The last line:
finger;*;guestA10000-2400
prevents the user from obtaining finger information from the system at any time.
Test yourself What would happen if I placed the following entry in /etc/security/time.conf?
*;*;*;!A10000-2400
If you guessed that this entry would deny access to all users, including root, you’re right. The point here is to be very careful when making modifications to the time.conf file. Always make a backup copy of this file before any modifications are made.
How to Manage Write CD Images in Linux?
create ISO image of cd data
# dd if=/dev/cdrom of=/home/abc/image.iso
mount this ISO image file in local
# mount -o loop -t iso9660 /home/abc/image.iso /xyz
Burning an .iso file works with the following command:
# cdrecord -v dev=0,0,0 /home/abc/image.iso
How to auto logout with terminal in Linux?
# vi /etc/bashrc
– in bottom of file write this line
TMOUT=20 # time in second
– then save and logout
Specify Download Speed / Download Rate Using wget limit-rate
$ wget –limit-rate=200k http://www.openss7.org/repos/tarballs/strx25-0.9.2.1.tar.bz2
Finding total size of files owned by a particular user
Example:
Foldername to search: /my-path
Username: user1
# find /my-path -user user1 -ls | awk ‘{sum += $7} END {printf “Total size: %8.4f MB\n”, sum/1024/1024}’
To find the last modified files in a directory you can use ls -ltr. To find the last modified file on a file system it will not work, but the following command will work:
#find /etc -type f -printf “%T@ %T+ %p” | sort -n
Unmount busy drives
You are probably all too familiar with the situation – you are trying to unmount a drive, but keep getting told by your system that it’s busy. But what application is tying it up? A quick one-liner will tell you:
$lsof +D /mnt/windows
This will return the command and process ID of any tasks currently accessing the /mnt/windows directory. You can then locate them, or use the kill command to finish them off.
Stat command can be used either to check the status/properties of a single file or the filesystem.
[root@feenix ~]# stat inventry.sh
File: `inventry.sh’
Size: 2721 Blocks: 8 IO Block: 4096 regular file
Device: 302h/770d Inode: 2046099 Links: 1
Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2012-05-05 16:15:58.000000000 +0530
Modify: 2012-05-05 08:39:41.000000000 +0530
Change: 2012-05-05 08:39:41.000000000 +0530
Finding all large files in the root filesystem
I have a linux server, which currently has below space usage:
/dev/sda3 20G 15G 4.2G 78% /
/dev/sda6 68G 42G 23G 65% /data
/dev/sda2 30G 7.4G 21G 27% /opt
/dev/sda1 99M 19M 76M 20% /boot
tmpfs 48G 8.2G 39G 18% /dev/shm
As you can see. / is at 78%. I want to check, which files or folders are consuming space.
I tried this:
find . -type d -size +100M
Which shows result like this:
./data/app/june01.dbf
./data/app/temp01.dbf
./data/app/smprd501.dbf
./home/feenixdv/centos.iso
./home/feenixdv/filegroup128.jar
Now this is my issue. I only want the name of those files located in folders that are consuming space at / and not at /data or /home. Since / is base of everything, it is showing me every file of my server.
Is is possible to get big files that is contributing to 78% of / ?
Answers:-
find / -xdev -type f -size +100M