LPIC-2 201-450 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Load average interpretation

The 1-, 5-, and 15-minute averages of runnable plus uninterruptible tasks; compare the value with the number of logical CPUs, since sustained load above that count signals oversubscription.

vmstat wa column

Percentage of CPU time spent waiting for I/O; a high wa value together with low user and system time points to a storage bottleneck rather than CPU shortage.

free available versus free

available estimates memory usable for new applications without swapping, including reclaimable page cache; free counts only completely unused RAM and is usually much smaller.

sar historical data

System Activity Reporter reads historical files under /var/log/sa; sar -u reports CPU, -r memory, -d disk, and -n DEV network; sadf exports data to CSV or XML.

iostat -x %util

Percentage of elapsed time during which the block device was busy; values near 100 indicate saturation, while await reports average request latency in milliseconds.

modprobe versus insmod

modprobe resolves dependencies from modules.dep and applies options from /etc/modprobe.d; insmod loads one .ko file directly and fails if dependencies are missing.

depmod function

Scans /lib/modules/$(uname -r) and writes modules.dep plus related maps so that modprobe can locate and order dependent kernel modules.

make oldconfig

Reuses the existing .config and prompts only for newly introduced kernel options; make localmodconfig instead creates a configuration limited to currently loaded modules.

initramfs purpose

Early userspace archive containing drivers and tools needed to mount the real root filesystem; generated by dracut, mkinitrd, or update-initramfs and stored in /boot.

sysctl persistent settings

Runtime kernel parameters exposed under /proc/sys; sysctl -w changes a value immediately, while /etc/sysctl.d/*.conf and /etc/sysctl.conf make it persist across reboots.

GRUB2 grub.cfg generation

grub-mkconfig -o /boot/grub/grub.cfg, or grub2-mkconfig, combines /etc/default/grub with executable scripts in /etc/grub.d to generate the active GRUB2 menu.

GRUB_DEFAULT variable

/etc/default/grub variable choosing the default menu entry by zero-based index, exact title, or saved; GRUB_SAVEDEFAULT records the last selected entry.

systemctl set-default

Sets the default.target symbolic link, normally multi-user.target or graphical.target; this replaces the traditional SysV default runlevel setting.

init=/bin/bash recovery

Kernel parameter that starts a shell instead of the init process; remount the root filesystem read-write with mount -o remount,rw / before making repairs.

LILO bootloader

Legacy bootloader configured through /etc/lilo.conf; any configuration change requires running lilo again to rewrite the boot sector, unlike GRUB2.

fstab sixth field

The sixth /etc/fstab field is the fsck pass number: 0 disables checking, 1 is used for the root filesystem, and 2 for other filesystems checked afterward.

noexec nosuid nodev

Security-related mount options: noexec prevents execution of binaries, nosuid ignores setuid and setgid bits, and nodev prevents interpretation of device nodes.

tune2fs -c and -i

Adjust ext2, ext3, or ext4 maximum mount count and interval between forced filesystem checks; tune2fs -l displays current superblock parameters.

cryptsetup luksOpen

Opens a LUKS encrypted container and maps it to /dev/mapper/name; an /etc/crypttab entry automates unlocking during system boot.

blkid and UUID mounts

Prints filesystem UUIDs and labels; using UUID= or LABEL= in /etc/fstab keeps mounts stable when device names change or disks are reordered.

mdadm and /proc/mdstat

Virtual file showing software RAID arrays, member disks, and resync or rebuild progress; mdadm --detail provides additional metadata and state information.

RAID 5 minimum devices

Requires at least three devices and tolerates one device failure; usable capacity is (n-1) disks because parity is distributed across all members.

lvextend -r option

Extends a logical volume and resizes its filesystem in one operation; works with ext4 through resize2fs and XFS through xfs_growfs when tools are present.

LVM snapshot creation

lvcreate -s creates a point-in-time copy using copy-on-write; the snapshot size must hold all changed blocks or the snapshot becomes invalid.

ip route default

ip route add default via GATEWAY installs the default route; ip route show lists current routes, and ip -6 manages IPv6 addresses and routes.

ss -tulpn

Lists TCP and UDP listening sockets with numeric ports and owning process names; elevated privileges are needed to see processes owned by other users.

NetworkManager nmcli

Command-line client for NetworkManager; nmcli connection add, modify, and up manage profiles, while nmcli device shows interface state and connectivity.

resolv.conf search directive

Appends listed domains to unqualified hostnames during DNS resolution; the ndots option sets how many dots a name needs before it is tried as absolute.

rsync -aAX

Archive mode preserves permissions, timestamps, and symlinks; -A preserves ACLs and -X extended attributes; --delete removes files absent from the source.

logrotate operation

Rotates, compresses, and deletes log files according to /etc/logrotate.conf and /etc/logrotate.d; usually triggered daily by cron or a systemd timer.

wall broadcast command

Broadcasts a message to all logged-in users' terminals; write targets a single user, and mesg y or mesg n controls whether messages are accepted.

DESTDIR make install

Staging variable for make install that redirects files into a temporary root; useful for packaging and for inspecting installed files without altering the running system.