Linux (Debian) Distros Hard Drives & File Systems

Transcription

1 Linux (Debian) Distros Debian GNU/Linux Debian based: Ubuntu, Knoppix, Linspire, Damn Small Linux, etc. Red Hat, Slackware, SUSE, Mandriva, CentOS, Gentoo, etc. Linux is just the kernel, it's what allows the system to boot up and talk with your machine's hardware. GNU (Recursive acronym: GNU's Not Unix ) was a project launched in 1984 to develop a complete Unix-line operating system which is free software. The GNU project was never able to develop a kernel, so that started using the Linux kernel to run all of their software on. Free Software? liberty, not necessarily price. Think of it as free speech, not as in free beer. Although, most open source software is free in both ways. Common items in Linux : Shell (text terminal/console), a graphical environment know has the X Window System, sometimes referred to as X11. GNOME or KDE desktop environment. Bar at the left/right/top/bottom is called the Panel (similar to taskbar in Windows ). Terminal Windows (console/shell window). Similar to Windows Command Prompt. Common partitions/directories: /, /home, /usr, /var, /tmp, swap Directory paths use forward slash / in Linux. (Backslash \ in Windows) Hard Drives & File Systems Managing your Hard drives in Linux: Gnome System Menu -> Administration -> Partition Manager: Allows you to see how your hard drive's partitions and the types of file systems that your partitions are using. Shell tools: fsck for checking hard drive for errors. cfdisk for partitioning drives. mkfs.ext3, mkfs.vfat, etc. to format the partition with a specific file system. Partitions are usually mounted to directory mount points. df command will show you which partitions are mounted to which directories. Mounting/Unmounted file systems (partitions) in linux: mount -t ext4 /dev/sda4 /mnt umount /mnt You can also use mount/umount to connect/disconnect network shares (like nfs shares): mount -t nfs :/share1 /mnt umount /mnt File systems are usually mounted at boot time via the /etc/fstab file. In Linux you need to have at least 2 partitions: / and swap. File Systems: ext (extended file system): The first file system ever created for linux. ext3 (third extended file system): 3 rd generation of the ext file system that now supports journaling along with a number of other improvements to the file system. ext2 and ext3 used to be the most common file systems used in linux, but now replaced by ext4. ext3 supports up to 16TB file systems, and 2TB file sizes. ext4 (fourth extended file system): 4 th generation of the ext file system which now upports up to 1EB file systems and 16TB file sizes. ext4 is also faster then all previous ext versions and has support for SSD drives via TRIM. reiserfs, xfs, zfs, etc. etc.

2 Advanced File System Features: Logical Volumes: Extending file systems (partitions) across multiple disks to create larger volumes and make it easier to expand in the future. Software & Hardware RAID - Redundant Array of Independent Disks (Inexpensive Drives). Bootup/Shutdown During the Linux install, some code is written to your hard drive's MBR (Master Boot Record) which tells your computer what files to load from your hard drive to load Linux. This program is usually either LILO (Linux Loader) or GRUB (GRand Unified Bootloader). With most linux boot loaders, you are presented with a boot screen that allows you to choose which kernel to boot. Runtime levels (init levels): 0: shutdown 1: single user mode 2: normal user mode 6: reboot For instance, this command will cause your system to reboot: /sbin/init 6 And this command will cause your system to shutdown: /sbin/init 0 Other command to shutdown and reboot your system: shutdown, halt, reboot Single User Mode allows you to troubleshoot your system and perform hardware/software maintenance. Similar to Windows Safe Mode. When was the machine last booted? From a Shell/Terminal run: uptime Locking Screen or Logging off: Gnome System Menu -> Lock Screen or Log Out Startup Scripts: /etc/rc#.d/* (# is 0, 1, 2, or 6) These scripts get run when entering or exiting a specific runtime level. Scripts will either start with an S (start) or K (kill), followed by a number to specify an order in which the scripts should run, for instance: /etc/rc2.d/s10syslog-ng, /etc/rc2.d/s89cron Account Management Creating and managing user accounts via Gnome System Menu -> Administration -> Users and Groups. Allows you to add, delete and change user accounts. Shell/Terminal: useradd -m -g users -u s /bin/tcsh -d /home/joe joe userdel -r joe /etc/passwd, /etc/shadow, /etc/group /etc/passwd contains account information: 7 fields: username:x:uid:gid:account Name:home dir:shell uid = user id number, integer gid = group id number /etc/shadow contains account password and other password settings: 9 fields: username:password:?:?:?:?:?:?:? /etc/group contains group information: 4 fields: groupname:password:gid:list of users for this group password is usually not used (usually an x ), and the list of users is comma separated like: video:x:44:demo,tom,mike New Account config files are stored in /etc/skel, they get copied over to the user's home directory (/home/username) when the account gets created. Groups: Users can be in multiple groups so that they can do specific things on the system. For instance, in order to be access your computer's cdrom drive, you must be part of the cdrom group. Or for printing, lpadmin group.

3 NIS (Network Information Services) aka YP (Yellow Pages): A client-server directory service protocol that allows you to share accounts between a server and clients. Quotas Enabling Quotas: Edit /etc/fstab and add the options usrquota,grpquota to any partition you want quotas enabled on. Reboot, then run: quotacheck -F vfsv0 -v -c /home Commands to control quotas: edquota: to setup (edit) a user's quota quota -v: To view a user's quota (they can only view their own) root can view all users' quota: quota -v username File Permissions Changing ownership and permissions on files and directories: Right-click on file or directory and choose Properties. Under the Permissions tab, you have the ability to set the different permissions for owner/group/other. 4 different types of permissions: read, write, execute, and none for owner/group/other. The chmod command allows you to set the permissions on files. The chown command allows you to change ownership of files (when root). Sample file permissions: rwxr-x--- root sys file1 read/write/execute for root, read/execute for group sys, none for other. Linux Memory Management RAM and Swap space. A swap file (virtual memory) is simply a file that linux will use in place of memory if it runs out of physical memory. Under the Gnome Application Menu -> System Tools -> System Monitor, Resources tab, allows you to see your physical and swap memory usage. Shell/Terminal: free command shows physical and swap memory usage. Networking Gnome System Menu -> Administration -> Network. Highlight the Wired interface and click Properties... So long as Roaming mode isn't selected, then you'll see that it's very similar to Windows, you can either use DHCP or manual (static info) for your network settings. If you Cancel out of that interface's properties, then you'll see the following tabs: Connections, General, DNS, Hosts. Shell/Terminal: ifconfig, hostname, netstat, ping Config files: /etc/network/interfaces (for Debian) Process/Job Management Under the Gnome Application Menu -> System Tools -> System Monitor, Process Table tab, allows you to see what processes are running your system system and kill them, End Process, if necessary. Allows you to see who is running the process, how much CPU resources or Memory a particular process is using, along with the process's PID (process ID #). Shell/Terminal: ps -aef more [list process] kill pid [kill process] kill -9 pid [forcefully kill process] top [interative process monitor]

4 Job Scheduling cron configuration files: /etc/crontab sample entry: 0 1 * * 1-3 root /command/to/run 7 fields: minute, hour, day of month, month, day of week, user, command Config Files Most configuration files in linux are plain text files. Files like /etc/hostname, /etc/passwd, /etc/shadow, /etc/fstab, /etc/crontab, etc,.etc. A lot of user configuration files in a user's home directory (/home/username or ~/username) are dot files like.cshrc,.bashrc,.profile. A large number of front end applications to edit config files (GUI based, text based, and web based). Daemons Programs that run in the background to perform some special function (SSH server, Remote Desktop, DNS server, DHCP server, event logging, etc.) Gnome System Menu -> Administration -> Services: Start, stop and disable services from here. 3 ways to startup jobs/daemons: 1. startup at bootup (vi /etc/rc scripts) 2. via cron, schedule job to run/startup at a specific time. 3. via inetd daemon: Startup daemons as needed. inetd daemon will run at all times, and will startup daemons (from /etc/inetd.conf) when needed. You can see what processes are running via shell/terminal: ps -aef more Logs System logs are logged via syslog-ng (or older syslog) daemon. Logs are normally stored in /var/log directory under different service name files. You can also see what your kernel is doing by running: dmesg Common log files: /var/log/syslog, /var/log/mail.log, /var/log/auth.log, etc. GUI vs TEXT Graphical: Point & Click. Large number of possible graphical environments: Xorg, Xfree86, Xgl are the X Window Systems. GNOME & KDE are the common desktop environments. Then you have the window managers: metacity, Compiz Fusion, etc. etc. Very customizable... Shell/Terminal: Easily write scripts to automate tasks. Easy to do remote administration via SSH. Shell Commands Number of different shells available: sh, csh, tcsh, bash, zsh, etc... Get help with man cmd Some general commands: cd, ls, mkdir, rmdir, rm, mv, cp, cat, more, echo Updates Linux update-manager for Debian takes care of updates (similar to Windows update manager). Shell/Terminal: apt-get update; apt-get upgrade Upgrading the system's kernel is usually the only time Linux ever needs to be rebooted, and even that now-a-days can sometimes be done without rebooting your system. (Compared to Windows, which requires a reboot with most updates).

5 Package Management Gnome System Menu -> Administration -> Synaptic Package Managerallows you to install and uninstall programs. Debian Linux Packages: DEB packages Red Hat Packages: RPM packages Debian Package installation: apt-get install package-name dpkg -i package-name.deb aptitude is a text based shell package manager. Compiling and installing software from source: tar xf package-name.tar./configure make make install Backups & File Compression The tar command is the easiest to use to archive a number of files into one file which you can then compress (with gzip or bzip2): tar cfp /tmp/new_file.tar /etc/hosts /etc/hostname [compress] tar xfp /tmp/new_file.tar [extract] Most commonly used file compression formats are gzip and bzip2 in linux: gzip /tmp/new_file.tar [gives you a new_file.tar.gz file] gunzip /tmp/new_file.tar.gz [gives us new_file.tar] bzip2 /tmp/new_file.tar [gives us new_file.tar.bz2] bunzip2 /tmp/new_file.tar.bz2 [gives us new_file.tar] dump/restore: Common unix/linux command for dumping files or entire partition to some backup area and restoring them as needed. Backup to tape, CD, DVD, or disk-to-disk (external USB drive, or NAS/SAN) Programming A large number of programming languages available for Linux: C, Java, Python, Perl, Shell scripts, etc. File Sharing Linux uses NFS (Network File System) was back in 1984 as a way for Unix systems to share their file systems between different machines. On the server export a directory via NFS by editing /etc/exports and adding an entry like so: /home/share (rw,sync,no_root_squash,subtree_check) /home/share2 *(ro,sync,no_root_squash,subtree_check) On the client, you use the mount command to access the share like so: mount -t nfs :/home/share1 /mnt [mount share] umount /mnt [unmount share] Access Window shares via Samba, you can mount a Windows share via: mount -t smbfs username=username,password //server/share_name /mnt (You will be prompted to type in a password)

6 Remote Management VNC (Virtual Network Computing): Remote Desktop protocol that is cross-platform, supported on: Windows, FreeBSD, MAC, Unix/Linux, etc. SSH (Secure SHell) access to shell/terminal from a remote location. Very secure, powerful and fast. Uses very little network bandwidth. Security File/Directory ownership/permissions Linux software firewall (iptables) Hardware Firewall for better protection Anti-Virus (Clamav): To protect other Windows system on network. Disable unneeded services (telnet, etc.) Miscellaneous Web: Apache Web Server Postfix Server Linux Text Editors: emacs, vi, gedit, etc...