Munchotaur
3/19/2015 - 5:32 AM
LFCS Study Outline 2015.02.28
LFCS Study Outline 2015.02.28
* LFCS Domains 2015.02
Note - the domains will change somewhat in March 2015. SW RAID
with mdadm will be removed
** The Command Line
*** Editing text files on the CLI
Covers the use of the basic text editors nano and gedit as well
as the advanced editors _vi_ and _emacs_
- nano
simple CLI-based text editor
- gedit
simple GUI-based text editor
- *vi/vim*
- invocation
+ vi -r myfile :: start vi and edit myfile in recovery mode
after a system crash - vim stores your changes in a swap
file. Using the original file plus the swap file, you can
mostly recover your work.
+ vi myfile :: edit myfile with vi
- _command mode_
initial mode that vim starts in
- movement
+ hjkl :: Left Down Up Right
+ H :: move to top of screen
+ L :: move to bottom of screen
+ 0 :: move to beginning of line
+ $ :: move to end of line
+ :0 or 1G or gg :: move to beginning of file
+ :n or nG :: move to line 'n'
+ :10 :: move to 10th line
+ 10G :: move to 10th line
+ :$ or G :: move to last line in file
+ C-f :: move forward one page
+ C-b :: move back one page
+ /pattern :: forward search for 'pattern'
+ ?pattern :: reverse search for 'pattern'
+ n :: move to next occurrence of search pattern
+ N :: move to previous occurrence of search pattern
+ C-g :: show position and line no; type _nG_ to go to
line number `n`
- editing
+ a :: append text after cursor
+ A :: append text at end of current line
+ I :: insert text at the beginning of current line
+ i :: insert text before cursor
+ o :: start new line below current line, insert text
+ O :: start new line above current line, insert text
+ Nx :: delete N chars, starting at current position
+ dw :: delete the word at the current position
+ D or d$ :: delete the rest of the current line
+ Ndd or dNd :: delete N lines
+ u :: undo the previous operation
+ C-R :: redo
+ yy :: yank(copy) the current line and put in buffer
+ Nyy or yNy :: yank N lines and put in buffer
+ p :: put after the current line
+ P :: put before the current line
- _insert mode_
from command mode, press 'i' to enter Insert mode
- _line mode_
from command mode, press ':' to enter Line mode
+ :r file2 :: read in file2 and insert at current position
+ :w :: write to the current file in buffer
+ :w myfile :: write out the file to myfile
+ :w! file2 :: overwrite file2
+ :x :: exit vi and write out modified file
+ :wq :: exit vi and write out modified file
+ :ZZ :: same as ':x', ':wq' save and exit vi
+ :q! :: quit vi without saving changes
+ external commands
+ :! wc % :: word count of current file (%)
+ :sh cmd :: open an external cmd shell; upon exit
resume vi session
+ %!fmt :: run current file through fmt and return results
- *emacs*
As emacs is our editor of choice, we know most of the
commands required for daily usage. We are only making note
of those cmds were weren't aware of previously
- C-o :: insert a blank line
- C-@ :: same as C-space (set mark)
- M-g-g-n :: goto line n
*** Manipulating text files on the CLI
- I/O Redirection
- read from '<'
- write to '>'
- append to '>>'
- Viewing files
- cat :: list file on stdout (no scrollback)
- tac :: list file on stdout in reverse order (no scrollback)
- less :: useful for viewing larger files as it provides scrollback
pauses at each screenful of text
- head :: print first 10 lines of a file by default
- tail :: print last 1o lines of a file by default
- head -n X | tail -n Y :: view a range of lines from text on stdin
+ _head -n 22 | tail -n 11_
Display from lines 12 to 22, inclusive. Note that _tail_ must
show the last *11* lines (22,21,20,19,18,17,16,15,14,13,12)
starting from 22 in order for line 12 to be included.
0-9: 10 numbers, 0-10: 11 numbers, 12-22: 11 numbers
- Manipulating Text
- cat :: concatenate - read, print, join, view files
+ cat file1 file2 :: concatenate multiple files and display output
+ cat file1 file2 > newfile :: concatenate multiple files and
redirect output to newfile (overwrites)
+ cat file >> file2 :: append file to end of file2
+ cat > file :: interactive mode; redirect stdin to file
Ctrl-d to terminate input
+ cat >> file :: interactive mode; append stdin to file
Ctrl-d to terminate input
+ *tac* can be used in all the same ways as above as it has
the same syntax as _cat_
- echo :: displays (echoes) text on stdout
is often used to redirect text to files and also display the
value of variables
+ echo -e :: use escaped char sequences like '\n' and '\t'
+ echo string > file :: write string to file
+ echo string >> file :: append string to file
+ echo $var :: print value of env. variable
- sed :: stream editor
filter and substitute text from an input source and move
to stdout or an output stream
- invocation
+ sed -e cmd <file> :: specify editing cmd, operate on
file and send result to stdout
+ sed -f scriptfile <file> :: specify a script containing
sed cmds, operate on file, send result to stdout
+ sed s/pattern/replace_str/ file :: substitute 1st string
occurrence in a line
+ sed s/pattern/replace_str/g file :: subtitute _pattern_ with
_replace_str_ globally (similar to vi _:s/foo/bar/g_)
+ sed 1,3s/pattern/replace_str/g file :: substitute all string
occurrences in lines 1 through 3
+ sed -i s/pattern/replace_str/g file :: edit files in-place
saves changes for string substitution in the same file; this
option is not recommended b/c it is irreversible; if you
absolutely must overwrite the original, '>' to a new file,
verify changes, and then '> originalFile'
** Filesystem and Storage
- *Archiving and Compressing files and directories*
+ Compressing files
_tar cvf(z) archive.tar(.gz) file1 file2 file3_
+ Compressing directories
_tar cvf(z) archive.tar(.gz) /path/to/dir_
When you run this command, make sure your /pwd/ is not
the directory you are trying to archive!
- *Assembling partitions as RAID devices*
1. Examine the drives which will compose the array
(Assume we have two drives, sdb and sdc)
_mdadm --examine /dev/sd[b-c]_
We want to make sure that there is no existing RAID
on the two disks ('no md superblock')
2. Create partitions with fdisk
_fdisk /dev/sdb_ (and later for /dev/sdc)
+ n :: create new partition ('1' for primary)
+ t :: change partition type ('fd' for Linux RAID auto)
+ w :: write changes and exit
Of course in between steps you want to use *p* to print the
partition table to check your work
3. Create RAID md devices
_mdadm -C /dev/md0 -l raid0 -n 2 /dev/sd[b-c]1_
+ -C or --create :: create md device
+ -l or --level :: RAID level (0,1,4,5,6,10)
linear, stripe, mirror, raid4, raid5, raid6, raid10,
multipath, faulty, container ...
+ -n or --raid-devices :: no. of RAID devices
4. Verify RAID device
_cat /proc/mdstat_
- *Creating LVM partitions* (LFCS & LFS201 topic)
1. Create Physical Volume (PV)
_pvcreate /dev/sdXY_
2. Create Volume Group (VG)
3. Create Logical Volume (LV)
4. Make file system on LV
_mkfs.ext[2,3,4,] /dev/VGname/LVname_
- *Configuring swap partitions*
1. _fdisk /dev/sdX_
n, p, 1, t, 82, w
normally swap partitions are designated as type 82, but
it is actually possible to use any partition type
2. _mkswap /dev/sdXY_
set up the linux swap area
3. _swapon /dev/sdXY_
enables the device for paging
4. edit /etc/fstab
_/dev/sdXY none swap defaults 0 0_
- *File attributes*
+ lsattr :: list file attributes
+ a :: append only
a file with 'a' attribute set can only be opened in
append mode for writing
+ c :: compressed
a file with 'c' attribute set is automatically compressed
on disk by the kernel, but reads from the file return
uncompressed data
+ d :: no dump
if this attribute is set, the file will not be backed
up when _dump_ is run
+ e :: extent format
if this attrib is set, it means the file is using
extents for mapping blocks on a disk
+ i :: immutable
a file with this attrib set cannot be modified, deleted,
renamed, and no link to the file can be created. This
attrib *even prevents su from deleting or modifying*
a file!
+ j :: data journalling
if this attrib is set, all its data is written to the
ext3 journal before being written to the file itself
+ s :: secure deletion
if this attrib is set on a file, when the file is deleted
all its block are zeroed and written back to the disk
+ t :: no tail-merging
if this attrib is set on a file, a partial block fragment
at the end of the file will _not_ be merged with other files
+ tail-merging :: efficiently use slack space at the end
of large files by packing the 'tail'/last partial block
of multiple files into a single bock
+ u :: undeletable
if a file has this attrib set, when the file is deleted
its contents are saved, allowing for the user to ask
for its undeletion
+ A :: no atime updates
if a file has this attrib set, when the file is accessed,
its atime record is not modified
+ atime :: time a file was last accessed
disabling this attribute can speed up file operations
+ C :: no copy on write
if a file has this attrib set, a fs supporting CoW
(Btrfs, for example) will not use CoW. CoW causes many
small random writes for large files, so CoW should be
disabled for DB files and VM images
+ D :: synchronous directory updates
+ S :: synchronous updates
+ T :: top of directory hierarchy
+ chattr :: change file attributes on Linux file systems
part of the _e2fsprogs_ package
+ -R :: Recursively change attribs of dir's and their
contents
+ -V :: verbose output
+ -f :: suppress error messages
shut the *f*uck up
+ -v :: version
+ _chattr -R +C /MULTIMEDIA/VM_
disable CoW recursively in dir .../VM and its sub-dirs
(+C means _no Copy-on-Write_)
- *Filesystem checking* (LFS201 topic)
+ e2fsck :: check ext2,3,4 fs
+ fsck :: a wrapper for fs-specific fs-checkers
- *Filesystem quotas and usage* (LFS201 topic)
https://wiki.archlinux.org/index.php/Disk_quota
+ install disk package quota
- quota-tools (Archlinux)
- quota (RHEL and Ubuntu)
+ set up file system quotas
+ user quota (edit /etc/fstab)
_/dev/sda1 /home ext4 defaults 1 1_
This is our fstab entry for 'home'. We will edit this to
enable a user disk quota
_/dev/sda1 /home ext4 defaults,usrquota 1 1_
+ group quota (edit /etc/fstab)
_/dev/sda1 /home ext4 defaults,usrquota,grpquota 1 1_
+ create quota files in the fs
_touch /home/aquota.user_
_touch /home/aquota.group_
+ remount partitions with quotas
_mount -vo remount /home_
+ create quota index
_quotacheck -vgum /home_
to create quota index for all partitions with quota
mount options in /etc/mtab
_quotacheck -vguma_
+ finally, enable quotas
_quotaon -av_
- Finding files on a filesystem
+ find
+ locate
+ ls
- Formatting filesystems
- ext2/3/4 filesystems
- mkfs
- XFS and btrfs filesystems
- Mounting filesystems automatically at boot time
you need to add an entry in /etc/fstab and make sure that the
mountpoint exists
- Mounting networked filesystems
1. NFS client config
_mount -t nfs(nfs4) -o servername:/remoteDir /local/mntpt_
2. Add NFS mount to /etc/fstab
_server:/remote/export /local/mntpt nfsType options 0 0_
_servername:/music /local/music nfs4 rsize=8192,wsize=8192,timeo=14,_netdev 0 0_
+ nfsTypes are _nfs_ (for nfs2,3) and _nfs4_
+ rsize :: the number of bytes used when reading from the server
+ wsize :: the number of bytes used when writing to the server
+ timeo :: the amount of time, in tenths of a second,
to wait before resending a transmission after an RPC timeout
+ _netdev :: wait until the network is up before
trying to mount the share. systemd assumes this for NFS,
but anyway it is good practice to use it for all types of
networked file systems
- Partitioning storage devices
- Troubleshooting filesystem issues
- *Linux Filesystem Tree Layout* (LFS201 topic)
- Linux Filesystem Hierarchy
+ /bin
+ /sbin
+ /lib
+ /usr/bin
+ /usr/sbin
+ /usr/lib
- *Linux Filesystems and the VFS* (LFS201 topic)
- Virtual Filesystems
+ /proc
+ /sysfs
- *Encrypting Disks with LUKS* (LFS201 topic)
+ create a LUKS partition
1. _cryptsetup luksFormat /dev/sdaX_
2. _cryptsetup open --type luks /dev/sdaX LUKSname_
** Local system administration
- Creating backups
t + tar cvf(z)
- Restoring backed up data
+ tar xvf(z)
- Creating local user groups
+ groupadd groupName
- Managing user accounts
+ user management
+ cat /etc/group
+ usermod :: modify user account
+ -a :: add to group
+ -G :: used with -a
+ group management
+ groupmod :: modify group definition
- Managing file permissions and ownership
+ chown :: change file or dir owner
+ -R :: recursively change ownership in dir and sub-dirs
+ chmod :: change rwx permissions
- Managing fstab entries
- Managing local user accounts
- Managing the startup process and related services
+ chkconfig
- Managing user account attributes
+ chmod
- Managing user processes
+ top (or htop)
+ ps
- Setting file permissions and ownership
- *System startup and shutdown* (LFS201 topic)
- init
+ systemV
+ upstart
+ systemd
- bootloader
+ GRUB
+ GRUB2
- *Kernel Services and Configuration* (LFS201 topic)
- *Kernel Modules* (LFS201 topic)
+ /proc/modules
+ lsmod
- *Devices and udev* (LFS201 topic)
+ udevadm :: udev management tool
- *Processes* (LFS201 topic)
- *Signals* (LFS201 topic)
- *System Monitoring* (LFS201 topic)
- *Process Monitoring* (LFS201 topic)
- *I/O monitoring and tuning* (LFS201 topic)
+ iotop
+ sar
- *I/O Scheduling* (LFS201 topic)
- *Memory: Monitoring Usage and Tuning* (LFS201 topic)
+ free
+ /proc/meminfo
- *Pluggable Authentication Modules (PAM)* (LFS201 topic)
- *Network Addresses* (LFS201 topic)
+ ip addr
+ ifconfig
- *Network Devices and Configuration* (LFS201 topic)
- *Basic Troubleshooting* (LFS201 topic)
- *System Rescue* (LFS201 topic)
- init 1, single-user mode
- LiveCD boot, chroot
** Local Security
- Accessing the root account
- Using sudo to manage access to the root account
+ _visudo_ for editing /etc/sudoers
+ usermod -a -G wheel userName (RHEL, Arch)
_usermod -a -G sudo userName_ (Ubuntu/Debian)
- *Linux Security Modules* (LFS201 topic)
+ Ubuntu
+ apt-get install pkgname
+ apt-get update
+ apt-get dist-upgrade
+ apt-get remove pkgname
** Shell scripting
- Basic Shell Scripting
** Software Management
- Installing software packages
+ RPM
+ DPKG
+ yum
+ APT