889 commands · 48 cheat sheets · 6 subcategories

Linux master quick reference — Page 3

Browse 244 commands from 12 focused cheat sheets on page 3 of 4. Each example opens its matching detailed section.

Processes, Services, and System · 17 commands

logrotate and Linux Log Retention Cheat Sheet

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Debug a configurationsudo logrotate --debug /etc/logrotate.confView examples
Run verboselysudo logrotate --verbose /etc/logrotate.confView examples
Test with isolated statesudo logrotate --state /run/app-logrotate.state \ --verbose /etc/logrotate.d/appView examples
Force a rotationsudo logrotate --force /etc/logrotate.d/appView examples
Rotate by sizesize 100MView examples
Cap between intervalsmaxsize 500MView examples
Keep archive generationsrotate 14View examples
Expire old archivesmaxage 90View examples
Use sortable date suffixesdateextView examples
Compress archivescompressView examples
Delay compressiondelaycompressView examples
Create replacement securelycreate 0640 app admView examples
Run scripts oncesharedscriptsView examples
Signal the writerpostrotateView examples
Copy then truncate in placecopytruncateView examples
Drop rotation identitysu app admView examples
Inspect rotation schedulingsystemctl status logrotate.timer logrotate.service \ --no-pagerView examples

Processes, Services, and System · 23 commands

systemd Services and Journal Cheat Sheet

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List loaded servicessystemctl list-units --type=serviceView examples
List installed unit filessystemctl list-unit-files --type=serviceView examples
Inspect service statussystemctl status nginx.serviceView examples
Test active statesystemctl is-active --quiet nginx.serviceView examples
Read unit propertiessystemctl show nginx.service \ --property=ActiveState,SubState,MainPIDView examples
Show unit sourcesystemctl cat nginx.serviceView examples
Show dependenciessystemctl list-dependencies nginx.serviceView examples
Start a servicesudo systemctl start nginx.serviceView examples
Stop a servicesudo systemctl stop nginx.serviceView examples
Restart a servicesudo systemctl restart nginx.serviceView examples
Reload service configurationsudo systemctl reload nginx.serviceView examples
Enable and startsudo systemctl enable --now nginx.serviceView examples
Disable and stopsudo systemctl disable --now nginx.serviceView examples
Reload unit definitionssudo systemctl daemon-reloadView examples
Create a drop-in overridesudo systemctl edit nginx.serviceView examples
Read one unit's journaljournalctl --unit=nginx.service --no-pagerView examples
Limit to current bootjournalctl --boot=0View examples
Read previous bootjournalctl --boot=-1View examples
Filter by timejournalctl --since='1 hour ago' --until=nowView examples
Filter error prioritiesjournalctl --priority=err --boot=0View examples
Follow a unit livejournalctl --follow --unit=nginx.serviceView examples
Emit JSON recordsjournalctl --unit=nginx.service --output=json --lines=20View examples
Read kernel messagesjournalctl --dmesg --boot=0View examples

Processes, Services, and System · 15 commands

systemd Timers and Scheduled Jobs Cheat Sheet

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List timerssystemctl list-timers --allView examples
Inspect one timersystemctl status backup.timerView examples
Read timer propertiessystemctl show backup.timer -p NextElapseUSecRealtime -p \ LastTriggerUSec -p TriggersView examples
Validate a calendarsystemd-analyze calendar 'Mon..Fri 02:00'View examples
Calendar scheduleOnCalendar=Mon..Fri *-*-* 02:00:00View examples
Catch a missed runPersistent=trueView examples
Delay after bootOnBootSec=15minView examples
Delay after activationOnUnitActiveSec=6hView examples
Set timing accuracyAccuracySec=1minView examples
Spread startsRandomizedDelaySec=30minView examples
Keep host delay stableFixedRandomDelay=trueView examples
Select activated unitUnit=backup.serviceView examples
Enable and start timersudo systemctl enable --now backup.timerView examples
Test work directlysudo systemctl start backup.serviceView examples
Read job logsjournalctl --unit=backup.service --since=todayView examples

Processes, Services, and System · 14 commands

udev Rules and Linux Device Events Cheat Sheet

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Inspect a deviceudevadm info --query=all --name=/dev/sdbView examples
Walk parent attributesudevadm info --attribute-walk --name=/dev/sdbView examples
Resolve sysfs pathudevadm info --query=path --name=/dev/sdbView examples
Monitor kernel and udev eventsudevadm monitor --kernel --udev --propertyView examples
Filter event monitoringudevadm monitor --udev --property \ --subsystem-match=blockView examples
Verify rule syntaxudevadm verify /etc/udev/rules.d/70-backup-disk.rulesView examples
Test rule evaluationudevadm test --action=add /sys/class/block/sdbView examples
Test a builtinudevadm test-builtin blkid /sys/class/block/sdbView examples
Reload rulessudo udevadm control --reloadView examples
Preview a trigger scopeudevadm trigger --dry-run --verbose \ --subsystem-match=blockView examples
Retrigger one devicesudo udevadm trigger --action=change \ /sys/class/block/sdbView examples
Check the event queueudevadm settle --timeout=10View examples
Read udev daemon logsjournalctl --unit=systemd-udevd --boot --no-pagerView examples
Export the udev databaseudevadm info --export-dbView examples

Storage and Filesystems · 20 commands

ext4, XFS, and Filesystem Repair Cheat Sheet

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Resolve a mount sourcefindmnt --target /srv/data -o \ TARGET,SOURCE,FSTYPE,OPTIONS,MAJ:MINView examples
Show block topologylsblk --fs --output \ NAME,KNAME,TYPE,FSTYPE,FSVER,LABEL,UUID,MOUNTPOINTSView examples
Probe filesystem metadatasudo blkid /dev/mapper/vg_data-lv_projectsView examples
Read device healthsudo smartctl --all /dev/nvme0n1View examples
Find storage errorsjournalctl -k -g \ 'I/O error|EXT4-fs error|XFS.*Corruption|nvme|ata' \ --since today --no-pagerView examples
Inspect ext metadatasudo dumpe2fs -h /dev/mapper/vg_data-lv_projectsView examples
Read-only ext checksudo e2fsck -f -n /dev/mapper/vg_data-lv_projectsView examples
Preen ext filesystemsudo e2fsck -f -p /dev/mapper/vg_data-lv_projectsView examples
List backup superblockssudo mke2fs -n /dev/mapper/vg_data-lv_projectsView examples
Show ext parameterssudo tune2fs -l /dev/mapper/vg_data-lv_projectsView examples
Show XFS geometrysudo xfs_info /srv/dataView examples
Create XFS metadata imagesudo xfs_metadump /dev/mapper/vg_data-lv_projects \ /recovery/projects.metadumpView examples
Check XFS without changessudo xfs_repair -n /dev/mapper/vg_data-lv_projectsView examples
Repair XFSsudo xfs_repair /dev/mapper/vg_data-lv_projectsView examples
Zero a corrupt XFS logsudo xfs_repair -L /dev/mapper/vg_data-lv_projectsView examples
Mount read-onlysudo mount -o ro /dev/mapper/vg_data-lv_projects \ /mnt/recoveryView examples
Mount ext without journal replaysudo mount -t ext4 -o ro,noload \ /dev/mapper/vg_data-lv_projects /mnt/recoveryView examples
Mount XFS without recoverysudo mount -t xfs -o ro,norecovery \ /dev/mapper/vg_data-lv_projects /mnt/recoveryView examples
Unmount normallysudo umount /srv/dataView examples
Find mount userssudo fuser -vm /srv/dataView examples

Storage and Filesystems · 30 commands

Linux Software RAID with mdadm Cheat Sheet

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List active MD arrayscat /proc/mdstatView examples
Inspect array geometrysudo mdadm --detail /dev/md/dataView examples
Inventory stable identitieslsblk -o \ NAME,PATH,SIZE,MODEL,SERIAL,TYPE,FSTYPE,MOUNTPOINTSView examples
Examine one MD superblocksudo mdadm --examine /dev/disk/by-id/ATA_MEMBER_A-part1View examples
Group discovered metadatasudo mdadm --examine --scanView examples
Create a named RAID1sudo mdadm --create /dev/md/data -l1 -n2 -e1.2 -N data \ -b internal /dev/disk/by-id/A-part1 \ /dev/disk/by-id/B-part1View examples
Create near-layout RAID10sudo mdadm --create /dev/md/data -l10 -p n2 -n4 \ /dev/disk/by-id/A-part1 /dev/disk/by-id/B-part1 \ /dev/disk/by-id/C-part1 /dev/disk/by-id/D-part1View examples
Assemble configured arrayssudo mdadm --assemble --scanView examples
Assemble explicit members read-onlysudo mdadm --assemble --readonly /dev/md/data \ /dev/disk/by-id/A-part1 /dev/disk/by-id/B-part1View examples
Stop an unused arraysudo mdadm --stop /dev/md/dataView examples
Mark a member faultysudo mdadm /dev/md/data --fail \ /dev/disk/by-id/ATA_FAILED-part1View examples
Detach a failed membersudo mdadm /dev/md/data --remove \ /dev/disk/by-id/ATA_FAILED-part1View examples
Add a replacement membersudo mdadm /dev/md/data --add \ /dev/disk/by-id/ATA_REPLACEMENT-part1View examples
Replace while the old disk readssudo mdadm /dev/md/data --replace \ /dev/disk/by-id/OLD-part1 --with \ /dev/disk/by-id/SPARE-part1View examples
Watch rebuild progresswatch -n 5 cat /proc/mdstatView examples
Read current sync actioncat /sys/block/md0/md/sync_actionView examples
Read precise sync progresscat /sys/block/md0/md/sync_completedView examples
Inspect per-array speed limitscat /sys/block/md0/md/sync_speed_min \ /sys/block/md0/md/sync_speed_maxView examples
Run one monitoring passsudo mdadm --monitor --scan --oneshotView examples
Add an internal bitmapsudo mdadm --grow /dev/md/data --bitmap=internalView examples
Remove a write-intent bitmapsudo mdadm --grow /dev/md/data --bitmap=noneView examples
Start a consistency checkecho check | sudo tee /sys/block/md0/md/sync_actionView examples
Read mismatch countcat /sys/block/md0/md/mismatch_cntView examples
Request consistency repairecho repair | sudo tee /sys/block/md0/md/sync_actionView examples
Grow a parity arraysudo mdadm --grow /dev/md/data -n4 \ --backup-file=/mnt/rescue/md-data.reshapeView examples
Reassemble with reshape backupsudo mdadm --assemble --scan \ --backup-file=/mnt/rescue/md-data.reshapeView examples
Print array configurationsudo mdadm --detail --scanView examples
Update Debian-family initramfssudo update-initramfs -uView examples
Update dracut initramfssudo dracut --forceView examples
Read physical-disk SMART datasudo smartctl -x /dev/disk/by-id/ATA_MEMBER_AView examples

Storage and Filesystems · 16 commands

Linux Storage and Filesystems Cheat Sheet

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Show block-device topologylsblk -o \ NAME,TYPE,SIZE,FSTYPE,FSVER,LABEL,UUID,MOUNTPOINTSView examples
Show filesystem overviewlsblk --fsView examples
Probe a specific devicesudo blkid /dev/sdb1View examples
List mounted filesystemsfindmnt --real --output TARGET,SOURCE,FSTYPE,OPTIONSView examples
Resolve a path's mountfindmnt --target /var/lib/appView examples
Test a mount pointmountpoint --quiet /mnt/archiveView examples
Show filesystem capacitydf -hT /var/lib/appView examples
Show inode capacitydf -ih /var/lib/appView examples
Measure one treedu -sh -- /var/lib/appView examples
Compare top-level childrendu -xhd1 -- /var/lib/app | sort -hView examples
Verify fstabsudo findmnt --verify --verboseView examples
Mount read-onlysudo mount --read-only --source /dev/sdb1 --target \ /mnt/reviewView examples
Unmount by targetsudo umount -- /mnt/reviewView examples
Synchronize one filesync --data /var/lib/app/database.dbView examples
Find mount userssudo fuser --mount --verbose /mnt/reviewView examples
Inspect open pathssudo lsof +D /mnt/reviewView examples

Storage and Filesystems · 35 commands

LVM Logical Volume Management Cheat Sheet

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Inventory physical volumessudo pvs -o \ pv_name,pv_uuid,vg_name,pv_size,pv_free,pv_attr,dev_sizeView examples
Inventory volume groupssudo vgs -o \ vg_name,vg_uuid,vg_size,vg_free,pv_count,lv_count,vg_attrView examples
Inventory logical volumessudo lvs -a -o \ lv_full_name,lv_size,segtype,lv_attr,origin,pool_lv,data_percent,metadata_percent,devicesView examples
Export a structured reportsudo lvm fullreport --reportformat json_stdView examples
Initialize a physical volumesudo pvcreate /dev/disk/by-id/wwn-0x5000c50012345678View examples
Create a volume groupsudo vgcreate vgdata \ /dev/disk/by-id/wwn-0x5000c50012345678View examples
Create a linear LVsudo lvcreate --name app --size 100G vgdataView examples
Extend an LV and filesystemsudo lvextend --resizefs --size +20G /dev/vgdata/appView examples
Consume remaining VG spacesudo lvextend --resizefs --extents +100%FREE \ /dev/vgdata/appView examples
Grow a mounted XFS filesystemsudo xfs_growfs /srv/appView examples
Test an LV reduction plansudo lvreduce --test --size 80G /dev/vgdata/archiveView examples
Reduce an LV after its filesystemsudo lvreduce --size 80G /dev/vgdata/archiveView examples
Create a thin poolsudo lvcreate --type thin-pool --name pool0 --size 500G \ vgdataView examples
Create a thin LVsudo lvcreate --type thin --name tenant1 --virtualsize \ 2T --thinpool vgdata/pool0View examples
Monitor thin-pool utilizationsudo lvs -o \ lv_full_name,segtype,lv_size,data_percent,metadata_percent,pool_lv,discardsView examples
Extend thin-pool datasudo lvextend --size +100G vgdata/pool0View examples
Extend thin-pool metadatasudo lvextend --poolmetadatasize +1G vgdata/pool0View examples
Create a COW snapshotsudo lvcreate --snapshot --name app-prechange --size 20G \ /dev/vgdata/appView examples
Monitor snapshot consumptionsudo lvs -o \ lv_full_name,origin,lv_size,data_percent,lv_attrView examples
Merge a snapshotsudo lvconvert --merge /dev/vgdata/app-prechangeView examples
Move extents between PVssudo pvmove /dev/disk/by-id/wwn-0x5000c50011111111 \ /dev/disk/by-id/wwn-0x5000c50022222222View examples
Remove an empty PV from a VGsudo vgreduce vgdata \ /dev/disk/by-id/wwn-0x5000c50011111111View examples
Tag a logical volumesudo lvchange --addtag production vgdata/appView examples
Select LVs by tagsudo lvs -o lv_full_name,lv_tags -S 'tags={production}'View examples
Activate one LVsudo lvchange --activate y vgdata/appView examples
Deactivate one LVsudo lvchange --activate n vgdata/appView examples
Disable LV autoactivationsudo lvchange --setautoactivation n vgdata/appView examples
Back up VG metadatasudo vgcfgbackup --file /var/backups/lvm/vgdata.conf \ vgdataView examples
List metadata archivessudo vgcfgrestore --list vgdataView examples
Test metadata restorationsudo vgcfgrestore --test --file \ /var/backups/lvm/vgdata.conf vgdataView examples
List the LVM devices filesudo lvmdevicesView examples
Check device-file entriessudo lvmdevices --checkView examples
Set thin-pool discard modesudo lvchange --discards nopassdown vgdata/pool0View examples
Report VG ownership and lockingsudo vgs -o \ vg_name,vg_uuid,vg_attr,vg_systemid,vg_locktypeView examples
Start shared-VG lockingsudo vgchange --lockstart vgsharedView examples

Storage and Filesystems · 20 commands

NFS and autofs Cheat Sheet

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List NFS mountsfindmnt -t nfs,nfs4 -o TARGET,SOURCE,FSTYPE,OPTIONSView examples
Show negotiated optionsnfsstat --mountsView examples
Query NFSv3 exportsshowmount --exports nfs1.example.netView examples
List RPC servicesrpcinfo -p nfs1.example.netView examples
Mount NFSv4.1sudo mount -t nfs4 -o vers=4.1,sec=krb5p \ nfs1.example.net:/projects /srv/projectsView examples
Mount read-only for validationsudo mount -t nfs4 -o ro,vers=4.1 \ nfs1.example.net:/projects /mnt/nfs-testView examples
Unmount normallysudo umount /srv/projectsView examples
Identify mount userssudo fuser -vm /srv/projectsView examples
Show active exportssudo exportfs -vView examples
Reload exportssudo exportfs -raView examples
Validate export syntaxsudo exportfs -ravView examples
Show server statisticsnfsstat --serverView examples
Show client statisticsnfsstat --clientView examples
Inspect per-mount statisticsmountstats /srv/projectsView examples
Check autofs mapssudo automount --dumpmapsView examples
Reload autofssudo systemctl reload autofs.serviceView examples
Show automount unitsfindmnt -t autofs -o TARGET,SOURCE,OPTIONSView examples
Read autofs logsjournalctl -u autofs.service --since today --no-pagerView examples
Check NFSv4 id mappingnfsidmap -lView examples
Inspect GSS servicessystemctl status rpc-gssd.service rpc-svcgssd.service \ --no-pagerView examples

Storage and Filesystems · 20 commands

Samba File Sharing Cheat Sheet

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Show Samba versionsmbd --versionView examples
Validate configurationtestparm --suppress-prompt /etc/samba/smb.confView examples
Inspect one sharetestparm --suppress-prompt --section-name projects \ /etc/samba/smb.confView examples
List configured servicestestparm --suppress-prompt --show-all-parameters \ /etc/samba/smb.confView examples
List server sharessmbclient --list=files1.example.net --user=aliceView examples
Open an SMB clientsmbclient //files1.example.net/projects --user=aliceView examples
Connect with Kerberossmbclient //files1.example.net/projects \ --use-kerberos=required --no-passView examples
Show active sessionssudo smbstatus --sharesView examples
Show locked filessudo smbstatus --locksView examples
Reload configurationsudo smbcontrol all reload-configView examples
Add a Samba passwordsudo smbpasswd -a aliceView examples
Disable a Samba accountsudo smbpasswd -d aliceView examples
Enable a Samba accountsudo smbpasswd -e aliceView examples
Read a share ACLsmbcacls //files1.example.net/projects / --user=aliceView examples
Read filesystem ACLsgetfacl --absolute-names /srv/samba/projectsView examples
Show protocol boundstestparm --suppress-prompt \ --parameter-name='server min protocol' \ /etc/samba/smb.confView examples
Show signing policytestparm --suppress-prompt \ --parameter-name='server signing' /etc/samba/smb.confView examples
Inspect SMB listenersss -ltnp 'sport = :445'View examples
Read smbd logsjournalctl -u smb.service -u smbd.service --since today \ --no-pagerView examples
Mount an SMB sharesudo mount -t cifs //files1.example.net/projects \ /mnt/projects -o \ credentials=/root/.smb-projects,vers=3.1.1View examples

Storage and Filesystems · 20 commands

Swap, zram, and Memory Pressure Cheat Sheet

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Summarize memoryfree --human --wideView examples
Read kernel memory countersgrep -E \ '^(MemAvailable|SwapTotal|SwapFree|Dirty|Writeback|Slab|SReclaimable):' \ /proc/meminfoView examples
List swap areasswapon --show --output=NAME,TYPE,SIZE,USED,PRIOView examples
Read kernel swap tablecat /proc/swapsView examples
Sample reclaim and swappingvmstat 1 10View examples
Read memory PSIcat /proc/pressure/memoryView examples
Sample swap activitysar -W 1 10View examples
Rank processes by RSSps -eo pid,user,comm,rss,vsz --sort=-rss | head -20View examples
Inspect one process memorysudo cat /proc/1234/smaps_rollupView examples
Find OOM eventsjournalctl -k -g 'oom|Out of memory|Killed process' \ --since today --no-pagerView examples
Read swappinesssysctl vm.swappinessView examples
Read overcommit policysysctl vm.overcommit_memory vm.overcommit_ratioView examples
Enable prepared swapsudo swapon --priority 10 /swapfileView examples
Disable one swap areasudo swapoff /swapfileView examples
List zram deviceszramctl --output \ NAME,ALGORITHM,DISKSIZE,DATA,COMPR,TOTAL,STREAMS,MOUNTPOINTView examples
Read zram memory statscat /sys/block/zram0/mm_statView examples
Configure a zram devicesudo zramctl /dev/zram0 --algorithm zstd --size 4GView examples
Reset an unused zram devicesudo zramctl --reset /dev/zram0View examples
Read zswap statecat /sys/module/zswap/parameters/enabledView examples
Read cgroup memory eventscat \ /sys/fs/cgroup/system.slice/example.service/memory.eventsView examples

Networking and Connectivity · 14 commands

curl and HTTP Debugging Cheat Sheet

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Include response headerscurl --include https://example.com/healthView examples
Request headers onlycurl --head https://example.com/assetView examples
Trace protocol exchangecurl --verbose https://example.com/healthView examples
Follow redirectscurl --location --max-redirs 5 https://example.com/oldView examples
Fail on HTTP errorscurl --fail-with-body https://example.com/apiView examples
Print status metadatacurl --silent --output /dev/null --write-out \ '%{http_code}\n' https://example.com/View examples
Send JSONcurl --json @payload.json https://api.example.com/itemsView examples
Add a headercurl --header 'Accept: application/json' \ https://api.example.com/itemsView examples
Upload a file bodycurl --upload-file ./artifact.bin \ https://upload.example.com/artifact.binView examples
Bound timecurl --connect-timeout 5 --max-time 30 \ https://example.com/View examples
Retry transient failurescurl --retry 3 --retry-all-errors --max-time 30 \ https://example.com/View examples
Save to an exact pathcurl --fail --output ./artifact.tar.gz \ https://example.com/artifact.tar.gzView examples
Use an explicit CA bundlecurl --cacert ./ca.pem https://internal.example/View examples
Measure phasescurl --output /dev/null --write-out \ 'dns=%{time_namelookup} connect=%{time_connect} total=%{time_total}\n' \ https://example.com/View examples
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