Raspian buster(Lite)でUARTコンソールを使う

タイトルそのまんま、UARTで操作したいときのためのメモ。
機材はRaspberry Pi 4B+、OSはRaspian buster Lite 2020-02-13版を使います。

Raspian OSは、デフォルトでUARTコンソールが有効になってません。
最初これに気づかず、minicomに何も出ない！って焦ったんですが、HDMI繋いだら普通に画面が出たので設定変更が必要と知った次第。

設定変更が必要なのは、Raspianを焼いてあるmicroSDカードの/bootパーティションにあるconfig.txt。

config.txtのなかみ（初期状態）

# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details
# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1
# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
#disable_overscan=1
# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16
# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720
# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1
# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=1
#hdmi_mode=1
# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2
# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4
# uncomment for composite PAL
#sdtv_mode=2
#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800
# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on
# Uncomment this to enable infrared communication.
#dtoverlay=gpio-ir,gpio_pin=17
#dtoverlay=gpio-ir-tx,gpio_pin=18
# Additional overlays and parameters are documented /boot/overlays/README
# Enable audio (loads snd_bcm2835)
dtparam=audio=on
[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2
[all]
#dtoverlay=vc4-fkms-v3d

UARTコンソールを使うためにはこのコンフィグテキストに

enable_uart=1

を追記します。
config.txtを書き換えたら、SDカードのアンマウントを行い、microSDをPiに差し込んで起動。

ちなみに、

ユーザ名　pi
パスワード　raspberry

でした。
~~（いろいろ試しちゃったのは内緒）~~

これでUARTからコンソール操作できるようになります。ただし、Linux Kernel起動からのログしか取れません（U-Bootまで?は見れない）。

出てきたKernelのブートログをそのまんまベタ張り。

Welcome to minicom 2.7.1
OPTIONS: I18n
Compiled on Aug 13 2017, 15:25:34.
Port /dev/ttyUSB0, 00:21:46
Press CTRL-A Z for help on special keys
[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 4.19.97-v7l+ (dom@buildbot) (gcc version 4.9.3 (cr0
[ 0.000000] CPU: ARMv7 Processor [410fd083] revision 3 (ARMv7), cr=30c5383d
[ 0.000000] CPU: div instructions available: patching division code
[ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
[ 0.000000] OF: fdt: Machine model: Raspberry Pi 4 Model B Rev 1.2
[ 0.000000] Memory policy: Data cache writealloc
[ 0.000000] cma: Reserved 256 MiB at 0x000000001ec00000
[ 0.000000] random: get_random_bytes called from start_kernel+0xc0/0x4e8 wit0
[ 0.000000] percpu: Embedded 17 pages/cpu s36928 r8192 d24512 u69632
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 1011008
[ 0.000000] Kernel command line: coherent_pool=1M 8250.nr_uarts=1 cma=64M cmt
[ 0.000000] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
[ 0.000000] Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
[ 0.000000] Memory: 3735564K/4050944K available (8192K kernel code, 687K rwd)
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] vector : 0xffff0000 - 0xffff1000 ( 4 kB)
[ 0.000000] fixmap : 0xffc00000 - 0xfff00000 (3072 kB)
[ 0.000000] vmalloc : 0xf0800000 - 0xff800000 ( 240 MB)
[ 0.000000] lowmem : 0xc0000000 - 0xf0000000 ( 768 MB)
[ 0.000000] pkmap : 0xbfe00000 - 0xc0000000 ( 2 MB)
[ 0.000000] modules : 0xbf000000 - 0xbfe00000 ( 14 MB)
[ 0.000000] .text : 0x(ptrval) - 0x(ptrval) (10208 kB)
[ 0.000000] .init : 0x(ptrval) - 0x(ptrval) (2048 kB)
[ 0.000000] .data : 0x(ptrval) - 0x(ptrval) ( 688 kB)
[ 0.000000] .bss : 0x(ptrval) - 0x(ptrval) ( 851 kB)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[ 0.000000] ftrace: allocating 28692 entries in 85 pages
[ 0.000000] rcu: Hierarchical RCU implementation.
[ 0.000000] NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
[ 0.000000] GIC: Using split EOI/Deactivate mode
[ 0.000000] arch_timer: cp15 timer(s) running at 54.00MHz (phys).
[ 0.000000] clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycless
[ 0.000005] sched_clock: 56 bits at 54MHz, resolution 18ns, wraps every 4398s
[ 0.000021] Switching to timer-based delay loop, resolution 18ns
[ 0.000246] Console: colour dummy device 80x30
[ 0.000708] console [tty1] enabled
[ 0.000768] Calibrating delay loop (skipped), value calculated using timer f)
[ 0.000804] pid_max: default: 32768 minimum: 301
[ 0.001087] Mount-cache hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.001119] Mountpoint-cache hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.001888] CPU: Testing write buffer coherency: ok
[ 0.002300] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
[ 0.002950] Setting up static identity map for 0x200000 - 0x20003c
[ 0.003122] rcu: Hierarchical SRCU implementation.
[ 0.003985] smp: Bringing up secondary CPUs ...
[ 0.004796] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
[ 0.005717] CPU2: thread -1, cpu 2, socket 0, mpidr 80000002
[ 0.006599] CPU3: thread -1, cpu 3, socket 0, mpidr 80000003
[ 0.006735] smp: Brought up 1 node, 4 CPUs
[ 0.006801] SMP: Total of 4 processors activated (432.00 BogoMIPS).
[ 0.006824] CPU: All CPU(s) started in HYP mode.
[ 0.006844] CPU: Virtualization extensions available.
[ 0.007642] devtmpfs: initialized
[ 0.017846] VFP support v0.3: implementor 41 architecture 3 part 40 variant 0
[ 0.018078] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, ms
[ 0.018121] futex hash table entries: 1024 (order: 4, 65536 bytes)
[ 0.025607] pinctrl core: initialized pinctrl subsystem
[ 0.026468] NET: Registered protocol family 16
[ 0.029185] DMA: preallocated 1024 KiB pool for atomic coherent allocations
[ 0.030634] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint.
[ 0.030666] hw-breakpoint: maximum watchpoint size is 8 bytes.
[ 0.030870] Serial: AMBA PL011 UART driver
[ 0.033951] bcm2835-mbox fe00b880.mailbox: mailbox enabled
[ 0.050025] raspberrypi-firmware soc:firmware: Attached to firmware from 202t
[ 0.060041] raspberrypi-firmware soc:firmware: Firmware hash is c3c8dbdf14760
[ 0.102647] bcm2835-dma fe007000.dma: DMA legacy API manager at (ptrval), dm1
[ 0.105860] vgaarb: loaded
[ 0.106236] SCSI subsystem initialized
[ 0.106442] usbcore: registered new interface driver usbfs
[ 0.106509] usbcore: registered new interface driver hub
[ 0.106597] usbcore: registered new device driver usb
[ 0.107849] clocksource: Switched to clocksource arch_sys_counter
[ 0.186411] VFS: Disk quotas dquot_6.6.0
[ 0.186516] VFS: Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
[ 0.186672] FS-Cache: Loaded
[ 0.186862] CacheFiles: Loaded
[ 0.187457] simple-framebuffer 3e513000.framebuffer: framebuffer at 0x3e5130)
[ 0.187494] simple-framebuffer 3e513000.framebuffer: format=a8r8g8b8, mode=16
[ 0.196747] Console: switching to colour frame buffer device 228x61
[ 0.205101] simple-framebuffer 3e513000.framebuffer: fb0: simplefb registere!
[ 0.214401] NET: Registered protocol family 2
[ 0.215110] tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 6144)
[ 0.215209] TCP established hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.215347] TCP bind hash table entries: 8192 (order: 4, 65536 bytes)
[ 0.215478] TCP: Hash tables configured (established 8192 bind 8192)
[ 0.215653] UDP hash table entries: 512 (order: 2, 16384 bytes)
[ 0.215741] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes)
[ 0.216012] NET: Registered protocol family 1
[ 0.216629] RPC: Registered named UNIX socket transport module.
[ 0.216700] RPC: Registered udp transport module.
[ 0.216756] RPC: Registered tcp transport module.
[ 0.216811] RPC: Registered tcp NFSv4.1 backchannel transport module.
[ 0.219858] Initialise system trusted keyrings
[ 0.220080] workingset: timestamp_bits=14 max_order=20 bucket_order=6
[ 0.229159] FS-Cache: Netfs 'nfs' registered for caching
[ 0.229742] NFS: Registering the id_resolver key type
[ 0.229822] Key type id_resolver registered
[ 0.229876] Key type id_legacy registered
[ 0.229937] nfs4filelayout_init: NFSv4 File Layout Driver Registering...
[ 0.232239] Key type asymmetric registered
[ 0.232298] Asymmetric key parser 'x509' registered
[ 0.232456] bounce: pool size: 64 pages
[ 0.232538] Block layer SCSI generic (bsg) driver version 0.4 loaded (major )
[ 0.232779] io scheduler noop registered
[ 0.232833] io scheduler deadline registered (default)
[ 0.235417] io scheduler cfq registered
[ 0.237796] io scheduler mq-deadline registered (default)
[ 0.240220] io scheduler kyber registered
[ 0.266765] brcm-pcie fd500000.pcie: dmabounce: initialised - 32768 kB, thre0
[ 0.269251] brcm-pcie fd500000.pcie: could not get clock
[ 0.271707] brcm-pcie fd500000.pcie: host bridge /scb/pcie@7d500000 ranges:
[ 0.274117] brcm-pcie fd500000.pcie: MEM 0x600000000..0x603ffffff -> 0xf800
[ 0.327885] brcm-pcie fd500000.pcie: link up, 5.0 Gbps x1 (!SSC)
[ 0.330509] brcm-pcie fd500000.pcie: PCI host bridge to bus 0000:00
[ 0.332868] pci_bus 0000:00: root bus resource [bus 00-01]
[ 0.335202] pci_bus 0000:00: root bus resource [mem 0x600000000-0x603ffffff])
[ 0.340487] PCI: bus0: Fast back to back transfers disabled
[ 0.342843] pci 0000:00:00.0: bridge configuration invalid ([bus 00-00]), reg
[ 0.348601] PCI: bus1: Fast back to back transfers disabled
[ 0.351000] pci 0000:00:00.0: BAR 8: assigned [mem 0x600000000-0x6000fffff]
[ 0.353368] pci 0000:01:00.0: BAR 0: assigned [mem 0x600000000-0x600000fff 6]
[ 0.355799] pci 0000:00:00.0: PCI bridge to [bus 01]
[ 0.358188] pci 0000:00:00.0: bridge window [mem 0x600000000-0x6000fffff]
[ 0.360798] pcieport 0000:00:00.0: enabling device (0140 -> 0142)
[ 0.363379] pcieport 0000:00:00.0: Signaling PME with IRQ 54
[ 0.365925] pcieport 0000:00:00.0: AER enabled with IRQ 54
[ 0.368491] pci 0000:01:00.0: enabling device (0140 -> 0142)
[ 0.373313] Serial: 8250/16550 driver, 1 ports, IRQ sharing enabled
[ 0.377681] iproc-rng200 fe104000.rng: hwrng registered
[ 0.380338] vc-mem: phys_addr:0x00000000 mem_base=0x3ec00000 mem_size:0x4000)
[ 0.383269] vc-sm: Videocore shared memory driver
[ 0.386056] gpiomem-bcm2835 fe200000.gpiomem: Initialised: Registers at 0xfe0
[ 0.398521] brd: module loaded
[ 0.410412] loop: module loaded
[ 0.413524] Loading iSCSI transport class v2.0-870.
[ 0.417525] libphy: Fixed MDIO Bus: probed
[ 0.420299] bcmgenet fd580000.genet: failed to get enet clock
[ 0.422635] bcmgenet fd580000.genet: GENET 5.0 EPHY: 0x0000
[ 0.424937] bcmgenet fd580000.genet: failed to get enet-wol clock
[ 0.427223] bcmgenet fd580000.genet: failed to get enet-eee clock
[ 0.429528] bcmgenet: Skipping UMAC reset
[ 0.432000] unimac-mdio unimac-mdio.-19: DMA mask not set
[ 0.447882] libphy: bcmgenet MII bus: probed
[ 0.488376] unimac-mdio unimac-mdio.-19: Broadcom UniMAC MDIO bus at 0x(ptrv)
[ 0.491511] usbcore: registered new interface driver r8152
[ 0.493843] usbcore: registered new interface driver lan78xx
[ 0.496156] usbcore: registered new interface driver smsc95xx
[ 0.498734] xhci_hcd 0000:01:00.0: xHCI Host Controller
[ 0.501008] xhci_hcd 0000:01:00.0: new USB bus registered, assigned bus numb1
[ 0.505400] xhci_hcd 0000:01:00.0: hcc params 0x002841eb hci version 0x100 q0
[ 0.508054] genirq: irq_chip Brcm_MSI did not update eff. affinity mask of i5
[ 0.511186] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, b9
[ 0.513517] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber1
[ 0.515856] usb usb1: Product: xHCI Host Controller
[ 0.518192] usb usb1: Manufacturer: Linux 4.19.97-v7l+ xhci-hcd
[ 0.520496] usb usb1: SerialNumber: 0000:01:00.0
[ 0.523302] hub 1-0:1.0: USB hub found
[ 0.525673] hub 1-0:1.0: 1 port detected
[ 0.528429] xhci_hcd 0000:01:00.0: xHCI Host Controller
[ 0.530710] xhci_hcd 0000:01:00.0: new USB bus registered, assigned bus numb2
[ 0.533001] xhci_hcd 0000:01:00.0: Host supports USB 3.0 SuperSpeed
[ 0.535639] usb usb2: New USB device found, idVendor=1d6b, idProduct=0003, b9
[ 0.538000] usb usb2: New USB device strings: Mfr=3, Product=2, SerialNumber1
[ 0.540330] usb usb2: Product: xHCI Host Controller
[ 0.542621] usb usb2: Manufacturer: Linux 4.19.97-v7l+ xhci-hcd
[ 0.544908] usb usb2: SerialNumber: 0000:01:00.0
[ 0.547671] hub 2-0:1.0: USB hub found
[ 0.550037] hub 2-0:1.0: 4 ports detected
[ 0.553484] dwc_otg: version 3.00a 10-AUG-2012 (platform bus)
[ 0.556189] usbcore: registered new interface driver uas
[ 0.558606] usbcore: registered new interface driver usb-storage
[ 0.561016] mousedev: PS/2 mouse device common for all mice
[ 0.564378] bcm2835-wdt bcm2835-wdt: Broadcom BCM2835 watchdog timer
[ 0.568070] sdhci: Secure Digital Host Controller Interface driver
[ 0.570251] sdhci: Copyright(c) Pierre Ossman
[ 0.572790] mmc-bcm2835 fe300000.mmcnr: could not get clk, deferring probe
[ 0.575389] sdhci-pltfm: SDHCI platform and OF driver helper
[ 0.580645] ledtrig-cpu: registered to indicate activity on CPUs
[ 0.583011] hidraw: raw HID events driver (C) Jiri Kosina
[ 0.585359] usbcore: registered new interface driver usbhid
[ 0.587567] usbhid: USB HID core driver
[ 0.590500] vchiq: vchiq_init_state: slot_zero = (ptrval), is_master = 0
[ 0.594074] [vc_sm_connected_init]: start
[ 0.600749] [vc_sm_connected_init]: end - returning 0
[ 0.604123] Initializing XFRM netlink socket
[ 0.606339] NET: Registered protocol family 17
[ 0.608632] Key type dns_resolver registered
[ 0.611037] Registering SWP/SWPB emulation handler
[ 0.613740] registered taskstats version 1
[ 0.615879] Loading compiled-in X.509 certificates
[ 0.624932] uart-pl011 fe201000.serial: cts_event_workaround enabled
[ 0.627160] fe201000.serial: ttyAMA0 at MMIO 0xfe201000 (irq = 34, base_baud2
[ 0.634691] console [ttyS0] disabled
[ 0.636908] fe215040.serial: ttyS0 at MMIO 0x0 (irq = 36, base_baud = 6250000
[ 2.318280] console [ttyS0] enabled
[ 2.324641] bcm2835-power bcm2835-power: Broadcom BCM2835 power domains drivr
[ 2.335094] brcmstb_thermal fd5d2200.thermal: registered AVS TMON of-sensor r
[ 2.345750] mmc-bcm2835 fe300000.mmcnr: mmc_debug:0 mmc_debug2:0
[ 2.354200] mmc-bcm2835 fe300000.mmcnr: DMA channel allocated
[ 2.388411] sdhci-iproc fe340000.emmc2: Linked as a consumer to regulator.3
[ 2.397890] sdhci-iproc fe340000.emmc2: Linked as a consumer to regulator.4
[ 2.425492] mmc1: queuing unknown CIS tuple 0x80 (2 bytes)
[ 2.435334] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
[ 2.444861] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
[ 2.452758] mmc0: SDHCI controller on fe340000.emmc2 [fe340000.emmc2] using A
[ 2.464942] of_cfs_init
[ 2.465214] mmc1: queuing unknown CIS tuple 0x80 (7 bytes)
[ 2.469858] of_cfs_init: OK
[ 2.479108] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
[ 2.490641] Waiting for root device PARTUUID=738a4d67-02...
[ 2.539004] random: fast init done
[ 2.578494] usb 1-1: new high-speed USB device number 2 using xhci_hcd
[ 2.598733] mmc0: new ultra high speed DDR50 SDHC card at address 0007
[ 2.608815] mmcblk0: mmc0:0007 SL16G 14.5 GiB
[ 2.617139] mmcblk0: p1 p2
[ 2.626897] mmc1: new high speed SDIO card at address 0001
[ 2.650226] EXT4-fs (mmcblk0p2): INFO: recovery required on readonly filesysm
[ 2.659982] EXT4-fs (mmcblk0p2): write access will be enabled during recovery
[ 2.770543] usb 1-1: New USB device found, idVendor=2109, idProduct=3431, bc1
[ 2.781204] usb 1-1: New USB device strings: Mfr=0, Product=1, SerialNumber=0
[ 2.790775] usb 1-1: Product: USB2.0 Hub
[ 2.798676] hub 1-1:1.0: USB hub found
[ 2.805007] hub 1-1:1.0: 4 ports detected
[ 10.380628] EXT4-fs (mmcblk0p2): recovery complete
[ 10.417342] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. )
[ 10.427937] VFS: Mounted root (ext4 filesystem) readonly on device 179:2.
[ 10.444228] devtmpfs: mounted
[ 10.457173] Freeing unused kernel memory: 2048K
[ 10.464363] Run /sbin/init as init process
[ 10.960779] systemd[1]: System time before build time, advancing clock.
[ 11.065471] NET: Registered protocol family 10
[ 11.073581] Segment Routing with IPv6
[ 11.117234] systemd[1]: systemd 241 running in system mode. (+PAM +AUDIT +SE)
[ 11.144735] systemd[1]: Detected architecture arm.
[ 11.171316] systemd[1]: Set hostname to .
[ 11.181391] systemd[1]: Failed to bump fs.file-max, ignoring: Invalid argumet
[ 11.808359] random: systemd: uninitialized urandom read (16 bytes read)
[ 11.825901] random: systemd: uninitialized urandom read (16 bytes read)
[ 11.835900] systemd[1]: Set up automount Arbitrary Executable File Formats F.
[ 11.852021] random: systemd: uninitialized urandom read (16 bytes read)
[ 11.861962] systemd[1]: Listening on udev Control Socket.
[ 11.879054] systemd[1]: Created slice system-systemd\x2dfsck.slice.
[ 11.892271] systemd[1]: Listening on udev Kernel Socket.
[ 11.904205] systemd[1]: Started Dispatch Password Requests to Console Direct.
[ 11.919012] systemd[1]: Listening on initctl Compatibility Named Pipe.

Raspbian GNU/Linux 10 raspberrypi ttyS0

raspberrypi login: pi
Password:
Linux raspberrypi 4.19.97-v7l+ #1294 SMP Thu Jan 30 13:21:14 GMT 2020 armv7l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

Wi-Fi is currently blocked by rfkill.
Use raspi-config to set the country before use.

pi@raspberrypi:~$ uname -a
Linux raspberrypi 4.19.97-v7l+ #1294 SMP Thu Jan 30 13:21:14 GMT 2020 armv7l GNx
pi@raspberrypi:~$ systemd-analyze
Startup finished in 10.911s (kernel) + 35.747s (userspace) = 46.658s
graphical.target reached after 35.704s in userspace
pi@raspberrypi:~$ lscpu
Architecture: armv7l
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 1
Vendor ID: ARM
Model: 3
Model name: Cortex-A72
Stepping: r0p3
CPU max MHz: 1500.0000
CPU min MHz: 600.0000
BogoMIPS: 108.00
Flags: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva id2
pi@raspberrypi:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
mmcblk0 179:0 0 14.5G 0 disk
�..�..mmcblk0p1 179:1 0 256M 0 part /boot
�..�..mmcblk0p2 179:2 0 14.2G 0 part /
pi@raspberrypi:~$ df -m
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/root 14288 1184 12493 9% /
devtmpfs 1825 0 1825 0% /dev
tmpfs 1954 0 1954 0% /dev/shm
tmpfs 1954 9 1945 1% /run
tmpfs 5 1 5 1% /run/lock
tmpfs 1954 0 1954 0% /sys/fs/cgroup
/dev/mmcblk0p1 253 53 200 21% /boot
tmpfs 391 0 391 0% /run/user/1000
pi@raspberrypi:~$ free -m
total used free shared buff/cache available
Mem: 3906 92 3735 8 78 3698
Swap: 99 0 99
pi@raspberrypi:~$