When using the nice command to start a process, by default the value 10 is assigned to it, that is, the priority is reduced. When a process is started without using nice, the assumed NICE value is 0.

Since the directory is not in the PATH, the form “report.sh“ can not be used, the ./report.sh should be used. Another way is to use the script as the command shell/bash shell (or sh, or ksh, etc).

The tr command will receive the string “Online Linux Training“ as input, the -d command will remove the entered characters generating the new output. Remember that everything is case sensitive, that’s why the “O“ of Online is not removed.

The touch command can be used to create a file without any content and also to change the dates of access and modification of a file.

The most common use of the dd command is to create an image from a partition, and vice versa, in that way the syntax uses if= to inform the source and of= to inform the destination.

In the tar command, the “t“ option displays the contents of the grouped/compressed file, the -f should always be used to indicate the .tar or .tgz file.

The rm command with the -r option removes a directory recursively, that is, removes the directory and everything inside. rmdir is only used to remove empty directories.

In “cat <<< linux“, the text after the <<< header is sent as input to the cat command, so the text is displayed. In “echo linux|cat“, the text output is also sent to the cat command and the text is displayed. In “echo linux 2> file“, only the error output is being redirected to the file file, the standard output is displayed on the screen.

The >log.out indication redirects the standard output (stout, value descriptor 1) to the log.out file. The indication 2>&1 says that the error output (stderr, value descriptor 2) must be associated with the same location that is associated with the standard output.

The ‘find /var -name “* 2015.log“‘ command will return all files in the /var directory ending with 2015.log, these files will be sent one by one as a parameter to the gzip command via xargs. , the xargs command is essential to do the intermediate between the output of the first command, and the delivery of the input to the gzip command, since it only works with one file at a time.

The tee command must be used to display an output on the screen while writing to a file, but by default the tee overwrites the file if it already exists, the -a option causes the tee to append to the file, including output at the end, without deleting the previous content.

SIGHUP can cause a process to die, to be restarted, or to reread its configuration files, with 1 being its numeric code. 9 is the code for SIGKILL, 10 for SIGUSR1 and 15 for SIGTERM.

In the shell, by default every command will be started in foreground mode, to force initialization as background, that is, unlinked from the shell, the & symbol at the end of the command should be used.

Option “a“ shows the processes of other users but linked to the current terminal. The “u“ option enables the user format, displaying the user name of each process as well as other details of the process. The “x“ option shows the processes of all terminals, as well as processes that are not associated with any terminal.

In general, load average allows you to check how the execution of processes on a system is. This value can be viewed by the uptime and top commands.

The uname command provides various system information, including the kernel-release, by the -r option.

The renice and top commands can be used to change the NICE value of a process that is already running. The nice command is used to set the value when starting a process.

In grep/egrep/fgrep, the -v option has the effect of not displaying the string or results of the expression used.

The -c option in grep/egrep counts the number of rows in which the string/expression is found. The expression “Class1+“ says that the character “1“ must be present in the string and may or may not be followed by other characters. This way you can find :Class1, Class11, Class12 and Class111

The EDITOR environment variable can be used to define the default text editor in the shell.

The option :q requests that the vi exit editing, but if the file has been changed you must use :q! to force the output of vi without saving the changes made. The commands :wq and ZZ are used to save and exit.

The “a“ option enters edit mode one character after the current cursor position. The “i“ option enters edit mode exactly at the current cursor position. The “o“ option enters edit mode on the line below the current cursor position.

Both fdisk and parted have the -l option to display the system partitions. The information is also always present in the /proc/partitions file. “Mount -a“ will mount all partitions defined as auto in /etc/fstab, but without any option it also displays mounted partitions.

The journaling feature was implemented in the ext3 filesystem, the only difference being with ext2.

The du command can be used to recursively check the disk space usage of files and directories. Df is used to show the use of system partitions.

The difference from ext3 to ext2 is the journaling feature, so the tune2fs command, with the -j option, to turn a device into ext3.

The -a option of the mount command will mount all partitions listed in /etc/fstab, except entries containing the “noauto“ option. Without any option, mount only displays the currently mounted partitions.

The first line information of /etc/fstab should be the device name (device, UUID or Label), the second should be the directory to be mounted. In the case of a swap partition, the second field can be described as “none“.

The partition must be unmounted so that the fsck command is used and the partition is checked. For this the first command to be executed must be the umount.

Permissions are set by subtracting the umask value from value 666 for files and 777 for directories. Thus, the value 022, which can also appear as 0022, will be 777 – 022 = 755 (rwxr-xr-x)).

Runlevel 0 is related to system shutdown and runlevel 6 to system reboot, so using 0 or 6 would make it impossible to boot the system.

Whenever a file has the letter “l“ at the beginning of its permissions, followed by 777 permissions, it is an indicator of being a symbolic link. You will also be able to see the following: link-name -> file/directory-destination

Which searches for files only in the directories included in the PATH. Whereis finds the binary files, libraries, source codes and manuals. Locate uses an internal database that contains the location of all system files.

The hypervisor is a required layer between the Infrastructure (aka Host) and the Virtual Machine itself, or Guest. The hypervisor controls and manages the access of virtual machines to the hardware elements of the infrastructure.

The gzip, bzip2 and xz commands are used for compression, just as the gunzip, bunzip2, and unxz commands are used for unpacking, respectively.

The characters [] define a list, and [0-9] indicates that all numeric characters are accepted. The keys {} indicate a quantifier, that is, how many occurrences of the previous character is expected. Remember that because it is an extended regular expression, the expression will only work with the use of the egrep or grep -E command.

Vim is an improvement on vi, in practice currently in most distributions the vi command is a link to vim. Other options are nano and emacs.

Btrfs natively supports features like subvolumes, snapshots, multi-devices/RAID and transparent data compression.

fdisk and parted can create GPT and MBR partitions. gdisk is specific to the GPT type.

SATA storage devices follow the same standard as SCSI disks, that is, /dev/sdX. ATA/IDE disks use the /dev/hdX standard.

IRQ stands for Interrut Request Line, or Interrupt Request. This information is recorded in the /proc/interrupts dynamic file.

After the boot process, the kernel invokes the /sbin/init process as the first system process, and it starts the other processes, so all other processes are children of the init process.

POST (Power-On Self-Test) is a BIOS procedure that checks if all devices are ready for use. The MBR (Master Boot Record) is the disk area that contains the information that will be used during the boot processs, GRUB is a boot manager and UEFI is a new firwmware being used in BIOS‘s place in modern systems.

The kernel supports a series of parameters that can be used at startup, such as quiet enable silent mode, not displaying startup and error messages. Other options are mem (maximum amount of RAM), ro (read only), splash (splash screen), among others.

In systemctl, the isolate option is used to switch between execute modes, or target (runlevels in SysV). For recovery mode (or single mode) the targets rescue.target or runlevel1.target are used.

If you use the ln command without any option, a hard link will be created. The most commonly used syntax is: ln

The /etc/inittab file shows the init process which is the default runlevel, by the parameter “initdefault“, and with that, which services should be started by the system.

In MBR partitioning, there is a limit of 4 primary partitions or 3 primary partitions and 1 extended partitions in which the logical partitions will be associated.

The LVM (Logical Volume Manager) has 5 main elements: VG (Volume Group), PV (Physical Volume), LV (Logical Volume), PE (Physical Extent) and LE (Logical Extent).

As the question mentions the file menu.lst, we are talking about the Legacy GRUB and in that standard hd0,3 indicates the fourth partition (since the count starts from 0) of the first disk. If it were GRUB2, hd0,3 would be the third partition of the first disk, ie / dev / hda3.

GRUB_DEFAULT = X indicates which system should be started by default. GRUB_TIMEOUT indicates the timeout before booting the kernel. The “default“ option indicates the default system in the GRUB Legacy and “root“ indicates the partition to be used.

The ldconfig command updates the /etc/ld.so.cache file information according to what is configured in the /etc/ld.so.conf file and the files in the /etc/ld.so.conf.d/ directory

Among the options presented, apt-cache depends shows the dependencies of a package, “apt“ has the same option. The command “dpkg -s vim“ would also return this information.

Apt-get update updates the package information contained in the configured repositories, but does not update the packages. The apt-get upgrade and dis-upgrade options are the ones used to perform the actual updates.

The dpkg command is used to install/update/remove packages directly, the -i option does the installation procedure. The apt-get and aptitude commands use the repositories as the source of the packages.

In the rpm command you must first enter the operating mode parameter, in this case the mode is the query, represented by -q, after that the option “f“ receives a file as parameter and rpm identifies the package related to it.

The -V or -verify option of rpm checks the integrity of a package.

The repositories are indicated in the files in the /etc/yum.repos.d/ directory. /etc/yum.conf refers to general YUM settings.

The export command causes a variable to become global, so that all child processes can work with the contents of this variable.

By default Linux, the .bash_history file in the user‘s $ HOME will contain the command execution history, being updated at the end of each user session.