Linux Important files


– Stores IP addresses and their corresponding hostname plus any aliases.

/etc/hosts.allow and /etc/hosts.deny
– list machines which are allowed or denied use of network services.

/etc/HOSTNAME or /etc/hostname
– contains the hostname for the local system.

– used to create mail aliases. Mail for root can be forwarded to another mail account.

– database files for the automounter daemon.

– store daily, weekly, etc. cron jobs.

– allows system administrator to define who can ftp to and from machine. Also define which machines can be used to access local ftp server.

– contain configuration and log directories for the Apache Web Server.

– define run levels; defines the default runlevel as 3.

– contains information on when each partition was backed up using the dump command.

– Boot loader configuration file.

– Message Of The Day – message which is displayed when user logs into the system. Maybe a warning message on usage or a funny message.

– contains user account information. Readable by everyone.

– contains actually passwords if using shadow passwords. Readable only by root.

– sendmail configuration files.

– system configuration files, i.e. pcmcia, network, etc.

– file system table – define partitions and their mount points.

– directory which contains system startup scripts.

– enable/disable network services. Can be used to disable ftp services or finger services, etc.


– System message files. View using any method used to view ascii files.

– Stores information on the last time each user logged into the system. Only viewable using the `last command`.

– Stores log files for web server

– Stores information on who is accessing your server.

– System information. Info on hardware errors and messages seen during boot. View using the `dmesg` command.

– Directory containing log files for the Samba Server (Allows Window based machines to access data on UNIX machines).

– contains mailbox files for each user. Created automatically when user account is created.

– Printer spooler directory.
is created when you define your printer. Printers can be local or remote.

– Directory contains crontab entries when created by users.

Mounting and Unmounting File Systems

– To mount a file system in the Linux directory tree, you must have a physical disk partition, CD-ROM, or floppy that you want to mount.
– You must also make sure that the directory to which you want to attach the file system, known as the mount point, actually exists.
– The mount point must exist before you try to mount the file system.
– Lets say you want to mount your Red Hat 6.2 CD:
– first, insert the CD into the CD-ROM drive
– then, as root, use the command: mount /dev/hdc /mnt/cdrom
– /dev/hdc = the device name for your CD-ROM drive
– /mnt/cdrom = the mount point. It is an empty directory that was created just for mounting your CD-ROM.
– Now when you want to read files from your CD-ROM, you will access it via the mount point, /mnt/cdrom. The system actually reads the date from /dev/hdc.
– Notice how /mnt/cdrom appears to be a part of the / file system. However, / is a hard disk partition and /mnt/cdrom is on your CD-ROM drive.
– The mount command is used to mount a disk and make it available for use.
– The umount command is used to dismount or un-mount a disk partition or CD-ROM. For example, to unmount the CD-ROM so you can eject the disk: umount /mnt/cdrom
– mount command options:
– -t type: specify the type of file system used on the device we are about to mount. Types include ext2 (linux native), msdos (MS-DOS), vfat (Windows 9x), ntfs (New Technology file system for WindowsNT), and iso9660(CD-ROM)just to name a few.
– Linux attempts to automatically determine the file system type. But it can not, then you must specify the type.
– -o list_of_options: These options allow you to mount the disk as read-only, read/write, whether root can access the data from a remote system(Not secure) and other things. Use the man command to find out more about mount’s options.

Mounting systems as boot time

– File systems that will be used all of the time should be mounted at boot time. For example, the / directory must be mounted when every we boot the system. If /home is on a separate disk, then it must be mounted before users log into the system. Or else, people can log in, but they have no home directory.
– /etc/fstab is the configuration file that defines which disk should be mounted and where (mount point).
– Fields in /etc/fstab:
– File System: Specifies the block device to be mounted from local or remote system.
– Mount Point: Specifies the mount point directory. For swap, this would be the word none.
– Type: Specify the type of file system being mounted.
– Mount options: comma-separated list of mount options.
– Dump Frequency: how often should the file system be backed up by the dump command.
– Pass Number: Specifies the order in which file systems should be checked by the fsck command when the system is booted. For / the value is 1, for all others (local only) the value is 2. NEVER check remote file systems.
– There is no mount point for swap partitions and the type is swap.
– The umount command unmounts a disk partition or CD-ROM. You can not remove, removable media until the drive has been unmounted. If you mount your CD-ROM, then push the button on the door, nothing happens. After unmounting the drive, then you can open the drive door.

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Tayfun DEĞER

Bu yazı blog üzerinde Tayfun DEĞER tarafından paylaşılmıştır. 2009 yılında açılan blog kısa zaman içerisinde büyük bir izleyici kitlesine sahip olmuştur. Tayfun DEĞER danışmanlık ve eğitimler vermektedir. vExpert 2013-2019, VCP4/5/6, VCP5-DT, VCP-Cloud ve MCSE sertifikalarına sahiptir.Twitter 'dan @tayfundeger veya RSS ile sitedeki değişiklikleri takip edebilirsiniz.

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